The great horned owl (''Bubo virginianus''), also known as the tiger owl (originally derived from early naturalists' description as the "winged tiger" or "tiger of the air"), or the hoot owl,
is a large
owl
Owls are birds from the order Strigiformes (), which includes over 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers a ...
native to the
Americas
The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World.
Along with th ...
. It is an extremely adaptable bird with a vast range and is the most widely distributed
true owl
The true owls or typical owls (family Strigidae) are one of the two generally accepted families of owls, the other being the barn owls (Tytonidae). This large family comprises 230 living or recently extinct species in 24 genera. The typical owl ...
in the Americas.
Its primary diet is
rabbits and hares,
rats and mice, and
vole
Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of lo ...
s, although it freely hunts any animal it can overtake, including
rodent
Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...
s and other small mammals, larger mid-sized
mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s,
bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
s,
reptile
Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
s,
amphibian
Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...
s, and
invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s. In ornithological study, the great horned owl is often compared to the
Eurasian eagle-owl
The Eurasian eagle-owl (''Bubo bubo'') is a species of eagle-owl that resides in much of Eurasia. It is also called the Uhu and it is occasionally abbreviated to just the eagle-owl in Europe. It is one of the largest species of owl, and femal ...
(''Bubo bubo''), a closely related species, which despite the latter's notably larger size, occupies the same ecological niche in
Eurasia
Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago a ...
, and the
red-tailed hawk
The red-tailed hawk (''Buteo jamaicensis'') is a bird of prey that breeds throughout most of North America, from the interior of Alaska and northern Canada to as far south as Panama and the West Indies. It is one of the most common members wit ...
(''Buteo jamaicensis''), with which it often shares similar habitat, prey, and nesting habits by day, thus is something of a diurnal ecological equivalent.
The great horned owl is one of the earliest nesting birds in
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
, often laying eggs weeks or even months before other raptorial birds.
Taxonomy
The great horned owl was
formally described in 1788 by the German naturalist
Johann Friedrich Gmelin
, fields =
, workplaces = University of GöttingenUniversity of Tübingen
, alma_mater = University of Tübingen
, doctoral_advisor = Philipp Friedrich GmelinFerdinand Christoph Oetinger
, academic_advisors =
, doctora ...
in his revised and expanded edition of
Carl Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...
's ''
Systema Naturae
' (originally in Latin written ' with the ligature æ) is one of the major works of the Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the system, now known as binomial nomen ...
''. He placed it with the other owls in the
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
''
Strix
Strix may refer to:
* Strix (mythology), a legendary creature of ancient Roman mythology
* ''Strix'' (bird), a genus of large "earless" wood-owls
* Strix Ltd, manufacturer of kettle controls, thermostats and water boiling elements for domestic ap ...
'' and coined the
binomial name
In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...
''Strix virginia''. Gmelin based his description on that of English naturalist
George Edwards who had described and illustrated the great horned owl in 1747 in the second volume of his ''A Natural History of Uncommon Birds''. Edwards had seen a live specimen from
Virginia
Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...
at the
house
A house is a single-unit residential building. It may range in complexity from a rudimentary hut to a complex structure of wood, masonry, concrete or other material, outfitted with plumbing, electrical, and heating, ventilation, and air condi ...
of the
Earl of Burlington
Earl of Burlington is a title that has been created twice, the first time in the Peerage of England in 1664 and the second in the Peerage of the United Kingdom in 1831. Since 1858, Earl of Burlington has been a courtesy title used by the duk ...
in
Chiswick
Chiswick ( ) is a district of west London, England. It contains Hogarth's House, the former residence of the 18th-century English artist William Hogarth; Chiswick House, a neo-Palladian villa regarded as one of the finest in England; and Full ...
. Edwards also owned a preserved specimen, and another specimen formed part of the
Leverian collection
The Leverian collection was a natural history and ethnographic collection assembled by Ashton Lever. It was noted for the content it acquired from the voyages of Captain James Cook. For three decades it was displayed in London, being broken up ...
. The great horned owl is now placed in the genus ''
Buco'' that was introduced in 1805 by
André Duméril.
The great horned owl represents one of the one or two radiations of the genus across the
Bering land bridge
Beringia is defined today as the land and maritime area bounded on the west by the Lena River in Russia; on the east by the Mackenzie River in Canada; on the north by 72 degrees north latitude in the Chukchi Sea; and on the south by the tip of ...
to the
Americas
The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World.
Along with th ...
. Whereas the Magellanic horned owl clearly divided once the owl had spread through the Americas, the consensus seems to be that the snowy owl and the great horned owl divided back in Eurasia and the snowy then spread back over the
Arctic
The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenla ...
through northernmost North America separately from the radiation of the horned owl.
The great horned and Eurasian eagle-owls may in fact be conspecifics, based on similarities in life history, geographic distribution, and appearance.[ In one case, a zoo-kept male great horned owl and female Eurasian eagle-owl produced an apparently healthy hybrid. Genetic testing indicates that the snowy owl, not the Eurasian eagle-owl, is the most closely related living species.][ ]Pleistocene era
The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...
fossils have been found of ''Bubo'' owls in North America, which may either be distinct species or paleosubspecies
A chronospecies is a species derived from a sequential development pattern that involves continual and uniform changes from an extinct ancestral form on an evolutionary scale. The sequence of alterations eventually produces a population that is p ...
, from as far east as Georgia
Georgia most commonly refers to:
* Georgia (country), a country in the Caucasus region of Eurasia
* Georgia (U.S. state), a state in the Southeast United States
Georgia may also refer to:
Places
Historical states and entities
* Related to the ...
, but predominantly in the Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
and to the west of them. Almost all fossils indicate these owls were larger than modern great horned owls.
A large number of subspecies
In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...
, more than 20 altogether, have been named. However, many of these are not true subspecies and only examples of individual or clinal variation. Subspecies differences are mainly in color and size and generally follow Gloger's and Bergmann's rule
Bergmann's rule is an ecogeographical rule that states that within a broadly distributed taxonomic clade, populations and species of larger size are found in colder environments, while populations and species of smaller size are found in warmer ...
s:[ The most conservative treatments of great horned owl subspecies may describe as few as 10,][ although an intermediate number is typical in most writings.][
Fifteen subspecies are currently recognised:][
* ''B. v. algistus'' ( Oberholser, 1904) – west Alaska
* ''B. v. lagophonus'' (Oberholser, 1904) – central Alaska to northeast Oregon, Idaho and northwest Montana (USA)
* ''B. v. saturatus'' Ridgway, 1877 – coastal southeast Alaska to coastal north California (USA)
* ''B. v. pacificus'' Cassin, 1854 – coastal central California (USA) to northwest ]Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
(Mexico)
* ''B. v. subarcticus'' Hoy, PR, 1853 – central west Canada to north Idaho (USA)
* ''B. v. pallescens'' Stone
In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition, and the way in which it is formed. Rocks ...
, 1897 – southwest USA to south Mexico
* ''B. v. pinorum'' Dickerman & Johnson, AB, 2008 – south Idaho to north Arizona and north New Mexico (USA)
* ''B. v. heterocnemis'' (Oberholser, 1904) – northeast Canada to the Great Lakes
The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lakes ...
region
* ''B. v. virginianus'' ( Gmelin, JF, 1788) – southeast Canada to central, east USA
* ''B. v. elachistus'' Brewster, 1902 – south Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
(Mexico)
* ''B. v. mayensis'' Nelson
Nelson may refer to:
Arts and entertainment
* ''Nelson'' (1918 film), a historical film directed by Maurice Elvey
* ''Nelson'' (1926 film), a historical film directed by Walter Summers
* ''Nelson'' (opera), an opera by Lennox Berkeley to a lib ...
, 1901 – Yucatán Peninsula
The Yucatán Peninsula (, also , ; es, Península de Yucatán ) is a large peninsula in southeastern Mexico and adjacent portions of Belize and Guatemala. The peninsula extends towards the northeast, separating the Gulf of Mexico to the north ...
(southeast Mexico)
* ''B. v. mesembrinus'' (Oberholser, 1904) – south Mexico to west Panama
* ''B. v. nigrescens'' Berlepsch, 1884 – Colombia to northwest Peru
* ''B. v. nacurutu'' (Vieillot
Louis Pierre Vieillot (10 May 1748, Yvetot – 24 August 1830, Sotteville-lès-Rouen) was a French ornithologist.
Vieillot is the author of the first scientific descriptions and Linnaean names of a number of birds, including species he collect ...
, 1817) – east Colombia through the Guianas to north, east Brazil, Argentina, Bolivia and central Peru
* ''B. v. deserti'' Reiser, 1905 – northeast Brazil (central north Bahia)
Description
The great horned owl is generally colored for camouflage.[ The underparts of the species are usually light with some brown horizontal barring; the upper parts and upper wings are generally a mottled brown usually bearing heavy, complex, darker markings. All subspecies are darkly barred to some extent along the sides, as well.
A variable-sized white patch is seen on the throat. The white throat may continue as a streak running down the middle of the breast even when the birds are not displaying, which in particularly pale individuals can widen at the belly into a large white area. South American great horned owls typically have a smaller white throat patch, often unseen unless actively displaying, and rarely display the white area on the chest.][ Individual and regional variations in overall color occur, with birds from the ]subarctic
The subarctic zone is a region in the Northern Hemisphere immediately south of the true Arctic, north of humid continental regions and covering much of Alaska, Canada, Iceland, the north of Scandinavia, Siberia, and the Cairngorms. Generally, ...
showing a washed-out, light-buff color, while those from the Pacific Coast
Pacific coast may be used to reference any coastline that borders the Pacific Ocean.
Geography Americas
Countries on the western side of the Americas have a Pacific coast as their western or southwestern border, except for Panama, where the Pac ...
of North America, Central America, and much of South America can be a dark brownish color overlaid with blackish blotching. The skin of the feet and legs, though almost entirely obscured by feathers, is black. Even tropical great horned owls have feathered legs and feet. The feathers on the feet of the great horned owl are the second-longest known in any owl (after the snowy owl
The snowy owl (''Bubo scandiacus''), also known as the polar owl, the white owl and the Arctic owl, is a large, white owl of the true owl family. Snowy owls are native to the Arctic regions of both North America and the Palearctic, breeding m ...
).[ The bill is dark gunmetal-gray, as are the talons.]
All great horned owls have a facial disc
In ornithology, the facial disc is the concave collection of feathers on the face of some birds—most notably owls—surrounding the eyes. The concavity of the facial disc forms a circular paraboloid that collects sound waves and directs those ...
. This can be reddish, brown, or gray in color (depending on geographical and racial variation) and is demarked by a dark rim culminating in bold, blackish side brackets. This species' "horns" are tufts of feathers, called plumicorns. The purpose of plumicorns is not fully understood, but the hypothesis that they serve as a visual cue in territorial and sociosexual interactions with other owls is generally accepted.[
]
Physiology and measurements
The great horned owl is the heaviest extant owl in Central
Central is an adjective usually referring to being in the center of some place or (mathematical) object.
Central may also refer to:
Directions and generalised locations
* Central Africa, a region in the centre of Africa continent, also known as ...
and South America and is the second-heaviest owl in North America, after the closely related, but very different-looking snowy owl.[ It is heavily built, with a barrel-shaped body, a large head, and broad wings.][ Its size can vary considerably across its range, with populations in interior ]Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
and Ontario
Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...
being largest and populations in California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
and Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
being smallest, though those from the Yucatán Peninsula
The Yucatán Peninsula (, also , ; es, Península de Yucatán ) is a large peninsula in southeastern Mexico and adjacent portions of Belize and Guatemala. The peninsula extends towards the northeast, separating the Gulf of Mexico to the north ...
and Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
appear to be even smaller. Adult great horned owls range in length from , with an average of , and possess a wingspan of , with an average of . Females are somewhat larger than males. Mean body weight is for females and for males. Depending on subspecies, maximum weight can reach .[.]
The wing chord length is . The wing loading
In aerodynamics, wing loading is the total mass of an aircraft or flying animal divided by the area of its wing. The stalling speed of an aircraft in straight, level flight is partly determined by its wing loading. An aircraft or animal with a ...
, the measured wing area compared to weight, is high, meaning the wings are relatively small in surface area for the bird's weight; the species' wing loading has been described as proportionately the highest among raptors. The tail
The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, r ...
, being relatively short as is typical of most owls, is long. Like other owl species, the great horned owl is capable of “silent flight”, which is the way owls fly while making almost no discernable noise, despite their large size. This is made possible thanks to three main components of the owl's wing structure. The leading edge of their feathers have serrations that help to disrupt the turbulence generated by wing flapping, then the softer feathers help deaden the sound, and finally the trailing fringe of the feathers that works to finish cutting the sounds made by flight. The structure of the great horned owl wing also allows it to fly at a very low speeds for the size of the species, as slow as 2 miles per hour when they are gliding on breezes.
The legs, feet, and talons are large and powerful. Tarsal length is .[ The average foot span of a fully spread foot, from talon to talon, is around , as compared to in ]long-eared owl
The long-eared owl (''Asio otus''), also known as the northern long-eared owlOlsen, P.D. & Marks, J.S. (2019). ''Northern Long-eared Owl (Asio otus)''. In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook o ...
s, in barn owls, and in the great grey owl
The great grey owl (''Strix nebulosa'') (also great gray owl in American English) is a very large owl, documented as the world's largest species of owl by length. It is distributed across the Northern Hemisphere, and it is the only species in th ...
. Great horned owls can apply at least 300 lb/in2 of crushing power in their talons, a pressure considerably greater than the human hand is capable of exerting. In some big females, the gripping power of the great horned owl may be comparable to much larger raptor species such as the golden eagle
The golden eagle (''Aquila chrysaetos'') is a bird of prey living in the Northern Hemisphere. It is the most widely distributed species of eagle. Like all eagles, it belongs to the family Accipitridae. They are one of the best-known bird of p ...
.
The hard, inflexible bill
Bill(s) may refer to:
Common meanings
* Banknote, paper cash (especially in the United States)
* Bill (law), a proposed law put before a legislature
* Invoice, commercial document issued by a seller to a buyer
* Bill, a bird or animal's beak
Plac ...
of the great horned owl is long, although the culmen, the exposed bill portion as measured along the top of the beak, is only .
The outer ear openings, which are concealed by feathers on the sides of the head, are relatively smaller than those of the Eurasian eagle owl, being in vertical axis, with the left ear slightly larger than the right. Like most exclusively (or near exclusively) nocturnal species, the great horned owl has asymmetrical ear holes that allow for the triangulation of sounds when hunting in the dark. The different-height holes, while still close together, are differentiated enough that the owl is able to use the timing and direction of the sound waves hitting each hole to precisely locate prey even if the prey is located under cover such as snow. The disc-like shape of their faces also helps to direct the sounds they hear toward their ears. While the true nature/purpose of the ear tufts that are present on the great horned owl is unknown, researchers agree that the tufts do not play any role in the hearing ability of the owl. It is estimated that their hearing is up to ten times that of a human being.
The great horned owl's eyes, just slightly smaller than the eyes of a human being
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedality, bipedalism and exceptional cognitive skills due to a large and complex Human brain, brain. This has enabled the development of ad ...
, are large even for an owl and rank proportionately among the largest eyes of all terrestrial vertebrates. The great horned owl has cylindrical eyes which creates more distance from the lens of the eye to the retina, which allows it to act more like a telephoto lens for farther distance sight compared to that possible from round eyes. They are visually highly adapted for nocturnal hunting and provide a wide, almost completely binocular field of view, a large cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...
l surface and a predominantly rod retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
. The great horned owl's eye contains both rods and cones like most species that see in color, but the vision of a great horned owl closely resembles that of many other nocturnal species. The peak wavelengths that are observed by the cones is 555 nm and the research suggests that the great horned owl has relatively weak color vision, especially compared to other bird species. Despite (or perhaps as a result of) the poorer sense of color vision, the owl manages to have excellent night vision. Instead of turning its eyes, an owl must turn its whole head, and the great horned owl can rotate its neck 270°. The iris
Iris most often refers to:
*Iris (anatomy), part of the eye
*Iris (mythology), a Greek goddess
* ''Iris'' (plant), a genus of flowering plants
* Iris (color), an ambiguous color term
Iris or IRIS may also refer to:
Arts and media
Fictional ent ...
is yellow, except in the amber-eyed South American great horned owl (''B. v. nacurutu'').
Calls
The great horned owl's song
A song is a musical composition intended to be performed by the human voice. This is often done at distinct and fixed pitches (melodies) using patterns of sound and silence. Songs contain various forms, such as those including the repetitio ...
is normally a low-pitched but loud (or also transcribed as , or , , ) and can last for four or five syllables. The call is resonant and has warranted descriptions as varied as "solemn" and "terrifying".[ The female's call is higher and rises in pitch at the end of the call. Female vocalizations are higher in pitch because of a smaller syrinx in the larger sex. Calling seems to peak after rather than before midnight.] Usually, territorial hooting decreases in February or March at the onset of egg laying. On occasion, this species exhibits "an indescribable assemblage of hoots, chuckles, screeches, and squawks, given so rapidly and disconnectedly that the effect is both startling and amusing". Descriptions of some of these odd sounds including a growling note pair, a laughing , a high-pitched ; a weak, soft , a cat
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
-like , a hawk
Hawks are bird of prey, birds of prey of the family Accipitridae. They are widely distributed and are found on all continents except Antarctica.
* The subfamily Accipitrinae includes goshawks, sparrowhawks, sharp-shinned hawks and others. Th ...
-like note of , and a nighthawk
The nighthawk is a nocturnal bird of the subfamily Chordeilinae, within the nightjar family, Caprimulgidae, native to the western hemisphere. The term "nighthawk", first recorded in the King James Bible of 1611, was originally a local name i ...
-like . These vocalizations may be variously uttered when the birds are disturbed and angered at the nest (frequently preceding an attack on an interloping human or other animal), represent the vocal development of young owls, or are given during courtship and during territorial disputes with other owls. Young owls still in the care of their parents make loud, persistent hissing or loud, piercing screeching sounds that are often confused with the calls of the barn owl.[
]
Subspecies
* Common/eastern great horned owl (''Bubo virginianus virginianus'')
:Eastern United States
The Eastern United States, commonly referred to as the American East, Eastern America, or simply the East, is the region of the United States to the east of the Mississippi River. In some cases the term may refer to a smaller area or the East C ...
eastwards from at least as far west as Minnesota
Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over to ...
to Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
; northeastwards in distribution to southern Quebec
Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...
, southern Ontario
Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...
, Nova Scotia
Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland".
Most of the population are native Eng ...
and Prince Edward Island
Prince Edward Island (PEI; ) is one of the thirteen Provinces and territories of Canada, provinces and territories of Canada. It is the smallest province in terms of land area and population, but the most densely populated. The island has seve ...
. Resident all-year.[ The race ''B. v. mesembrinus'' from Central America south of the ]Isthmus of Tehuantepec
The Isthmus of Tehuantepec () is an isthmus in Mexico. It represents the shortest distance between the Gulf of Mexico and the Pacific Ocean. Before the opening of the Panama Canal, it was a major overland transport route known simply as the Te ...
, may be merely a southerly leg of this race, as its coloring is almost exactly the same as ''virginianus'', although with rather smaller body size. However, ''mesembrinus'' type owls are discontinuous in range, with only paler owls from ''pallescens'' and ''mayensis'' found in the in-between range before the northern ''virginianus'' reappears back up in South Texas.[
:The "nominate race" is a medium-hued form, neither darkly saturated nor strikingly pale. Darker gray or somewhat paler individuals are known. It tends to be richly tinged with rufous and barred distinctly blackish-brown below with rather soft contrast. The feet can range from tawny to buff to creamy and are the legs are typically barred dark to a moderate extent. The facial disc is often a solid cinnamon-red color. This is mid-to-large race, with a wing chord length of , averaging , in males and , averaging , in females.] Unexpectedly, although it is not the longest-winged, the nominate is the heaviest known race as males weigh from , averaging , and females weigh from , averaging ; the prior figures originally from a huge sample around Michigan
Michigan () is a state in the Great Lakes region of the upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the 10th-largest state by population, the 11th-largest by area, and the ...
. In comparison, ''B. v. subarcticus'', though averaging longer in wing length averages somewhat less heavy.[ On the contrary, in ]Costa Rica
Costa Rica (, ; ; literally "Rich Coast"), officially the Republic of Costa Rica ( es, República de Costa Rica), is a country in the Central American region of North America, bordered by Nicaragua to the north, the Caribbean Sea to the no ...
, within the range of the possibly synonymous ''mesembrinus'', great horned owls average approximately , the lightest average mass reported anywhere for this species. Other standard measurements of this race are a tail length of , a tarsus length of about and a bill length of .[ ''B. v. virginianus'' also tends to have relatively the longest ear tufts on any race.][
* South American great horned owl (''Bubo virginianus nacurutu'')
:A lowland form occurring in disjunct populations from eastern ]Colombia
Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...
to the Guyanas
The Guianas, sometimes called by the Spanish loan-word ''Guayanas'' (''Las Guayanas''), is a region in north-eastern South America which includes the following three territories:
* French Guiana, an overseas department and region of France
* G ...
; also from Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
and Uruguay
Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...
south of the Amazon Basin
The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Bolivi ...
to Bolivia
, image_flag = Bandera de Bolivia (Estado).svg
, flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center
, flag_alt2 = 7 × 7 square p ...
, the Buenos Aires Province
Buenos Aires (), officially the Buenos Aires Province (''Provincia de Buenos Aires'' ), is the largest and most populous Argentine province. It takes its name from the city of Buenos Aires, the capital of the country, which used to be part of th ...
in northern Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
and western Paraguay
Paraguay (; ), officially the Republic of Paraguay ( es, República del Paraguay, links=no; gn, Tavakuairetã Paraguái, links=si), is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to th ...
; resident all-year. Includes the proposed subspecies ''scotinus'', ''elutus'', and ''deserti''. The status of this form, especially the relationships between the scattered subpopulations and with ssp. ''nigrescens'' and the Magellanic horned owl, deserves more study.
:Dull, earthy brownish color is typical; birds from the semiarid interior of Brazil often have much white on uppertail- and ear-coverts against a dull gray background (sometimes separated as ''deserti''). This race is less fuscous than ''nigrescens''. It is the only subspecies where the iris
Iris most often refers to:
*Iris (anatomy), part of the eye
*Iris (mythology), a Greek goddess
* ''Iris'' (plant), a genus of flowering plants
* Iris (color), an ambiguous color term
Iris or IRIS may also refer to:
Arts and media
Fictional ent ...
is amber, not yellow. The Magellanic horned owl, while somewhat similar in coloring, has yellow eyes like other horned owls, not amber eyes. ''B. v. nacurutu'' is a medium-sized race, smaller than most in North America but not as small as some of the Mexican races. The wing chord length is in males and in females. The tail in both sexes can range from . Only three birds have had published weights, two males scaling and one female weighing . The most notable feature of this race is its large bill, at , which is the biggest of any horned owl race despite the otherwise moderate size of ''B. v. nacurutu''.[
* Northern/sub-Arctic great horned owl (''Bubo virginianus subarcticus'')
:Breeding range from ]Mackenzie, British Columbia
Mackenzie is a district municipality within the Fraser-Fort George Regional District in central British Columbia, Canada. The community is located at the south end of Williston Lake. The townsite, established by Alexandra Forest Industries (acqu ...
region east to the southern Hudson Bay
Hudson Bay ( crj, text=ᐐᓂᐯᒄ, translit=Wînipekw; crl, text=ᐐᓂᐹᒄ, translit=Wînipâkw; iu, text=ᑲᖏᖅᓱᐊᓗᒃ ᐃᓗᐊ, translit=Kangiqsualuk ilua or iu, text=ᑕᓯᐅᔭᕐᔪᐊᖅ, translit=Tasiujarjuaq; french: b ...
; southern limit unclear but at least reaches to Montana
Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...
and North Dakota
North Dakota () is a U.S. state in the Upper Midwest, named after the Native Americans in the United States, indigenous Dakota people, Dakota Sioux. North Dakota is bordered by the Canadian provinces of Saskatchewan and Manitoba to the north a ...
. Non-breeding birds are regularly found south to latitude
In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...
45°S, i.e. Wyoming
Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...
or South Dakota
South Dakota (; Sioux language, Sioux: , ) is a U.S. state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota people, Lakota and Dakota peo ...
, occasionally ranging beyond this limit especially in years with low prey in the north. This race includes the birds described as ''occidentalis'' (based on a wintering individual, as was the original ''subarcticus'') and ''sclariventris''. The older name ''wapacuthu'' was occasionally used for this subspecies, but it cannot with certainty be assigned to a recognizable taxon
In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...
and is thus considered a '' nomen dubium''. The population described as ''algistus'' is probably based on wandering individuals and/or various intergrades of ''subarcticus'' with other races.[
:This is the palest form of horned owl, with the ground color essentially whitish with a faint buff tinge above; black underside barring variable from indistinct to pronounced, being most often prominent on the upper chest amongst otherwise pale plumage. This race shows little to no reddish coloration. ''B. v. subarcticus'' shows a very high degree of clinal variation, ranging from in the ]Contiguous United States
The contiguous United States (officially the conterminous United States) consists of the 48 adjoining U.S. states and the Federal District of the United States of America. The term excludes the only two non-contiguous states, Alaska and Hawaii ...
where owls are often medium-grayish and more heavily marked to the subarctic
The subarctic zone is a region in the Northern Hemisphere immediately south of the true Arctic, north of humid continental regions and covering much of Alaska, Canada, Iceland, the north of Scandinavia, Siberia, and the Cairngorms. Generally, ...
zone in Canada where very pale birds with almost non-existent markings are prominent. Very pale birds are similar to a young female snowy owl from a distance. In this race, the feet range from immaculate white to buff, with little or no mottling.[ In the west of Canada, ''subarcticus'' may hybridize with the dark ''saturatus'' and may do the same with this similarly dark ''heterocnemis'' in the east. In both cases, they may produce intermediate looking hybrids of reddish tone, like a ''virginianus'' but with sharper contrasting of colors.] This is one of the largest-bodied subspecies. The wing chord length is , averaging , in males and , averaging , in females. Body mass ranges from , averaging , in males and from , averaging , in females. Tail length is and in males and females, respectively. Bill length is in both and one bird had a tarsus of .[
* California great horned owl (''Bubo virginianus pacificus'')
:Central and southern California west of the ]Sierra Nevada
The Sierra Nevada () is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primarily ...
except for the San Joaquin Valley
The San Joaquin Valley ( ; es, Valle de San Joaquín) is the area of the Central Valley of the U.S. state of California that lies south of the Sacramento–San Joaquin River Delta and is drained by the San Joaquin River. It comprises seven c ...
, south to Northwestern Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
, Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
. Intergrades with ''pallescens'' in San Diego County
San Diego County (), officially the County of San Diego, is a county in the southwestern corner of the U.S. state of California. As of the 2020 census, the population was 3,298,634, making it California's second-most populous county and the fi ...
, California (see also below). Resident all-year.[
:Very rich brown, dark underside barring distinct, less pronounced than in ''saturatus'' but more pronounced than in ''pallescens''. ]Humeral
The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a rou ...
area is black. Feet are mottled dark. The facial disc is often even darkly mottled.[ This is a fairly small-bodied race, in fact including the lightest wild great horned owl adult ever weighed. The wing chord length is , averaging , in males and , averaging , in females. Body mass ranges from , averaging , in males and from , averaging , in females. Tail length is and in males and females, respectively. Bill length is and one bird had a tarsus of .][
* Coastal great horned owl (''Bubo virginianus saturatus'')
:]Pacific
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
coast from southeastern Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
to northern California. Includes the previously described form of ''B. v. leucomelas''. The often-recognized race ''B. v. lagophonus'' is often now considered a mere clinal variation of the same race from interior Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
to Oregon
Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...
, the Snake River
The Snake River is a major river of the greater Pacific Northwest region in the United States. At long, it is the largest tributary of the Columbia River, in turn, the largest North American river that empties into the Pacific Ocean. The Snake ...
, and northwestern Montana
Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...
.[ These forms may be reported in winter as far south as ]Colorado
Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...
and Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
, but these are in times of irruption.
:A dark and overall brownish form with heavily barred and mottled underside, with a dull tawny base. Inland birds (''lagophonus'') tend to have a more grayish base, the coastal owls being more richly brown. Otherwise, inland and coastal owls are practically the same. The facial disc can range from gray to reddish-gray to dark rufous. The feet are fairly dusky gray typically, although some buff-footed individuals are known, and legs are more prominently barred with black than in other North American races.[ This is a large race going on linear measurements, which in ]Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
n owls outmatch those of all other races but for ''heterocnemis'' in Ontario
Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...
(which may itself be a discontinuous eastern wing of this race). The wing chord length is , averaging , in males and , averaging , in females. Tail length is and in males and females. In both sexes, known bill and tarsal lengths are and . No weights are known to have been published.[
* North Andean great horned owl (''Bubo virginianus nigrescens'')
:]Andes
The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...
; arid temperate
In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...
and puna zones from Colombia
Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...
to northwestern Peru
, image_flag = Flag of Peru.svg
, image_coat = Escudo nacional del Perú.svg
, other_symbol = Great Seal of the State
, other_symbol_type = Seal (emblem), National seal
, national_motto = "Fi ...
. Resident all-year round. Presumably synonymous with the described ''columbianus''.[
:A dark, cold gray-brown form with heavy fuscous blotching. Arguably this is the darkest colored race on average, though it could be rivaled by individuals from ''saturatus'' and ''elachistus''. This race has only minimally the rufous tinge seen in other darkish races, although some ''nigrescens'' may have a cinnamon facial disc.][ The largest winged race of owl in South America, this owl has a wing chord length of in males and in females. The tail in both sexes can range from . Bill length is , again relatively long as in ''nacurutu'' and one bird had a tarsal length of , indicating relatively long legs in the race. No published weights are known.][ Apparently, despite its sizeable wing area, ''nigrescens'' is notably smaller overall when specimens are compared side-by-side with those from ''saturatus''.][
* Desert great horned owl (''Bubo virginianus pallescens'')
:]San Joaquin Valley
The San Joaquin Valley ( ; es, Valle de San Joaquín) is the area of the Central Valley of the U.S. state of California that lies south of the Sacramento–San Joaquin River Delta and is drained by the San Joaquin River. It comprises seven c ...
southeastwards through arid regions of southeastern California and southern Utah
Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
eastwards to western Kansas
Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the ...
and southwards to Guerrero
Guerrero is one of the 32 states that comprise the 32 Federal Entities of Mexico. It is divided in 81 municipalities and its capital city is Chilpancingo and its largest city is Acapulcocopied from article, GuerreroAs of 2020, Guerrero the pop ...
and western Veracruz
Veracruz (), formally Veracruz de Ignacio de la Llave (), officially the Free and Sovereign State of Veracruz de Ignacio de la Llave ( es, Estado Libre y Soberano de Veracruz de Ignacio de la Llave), is one of the 31 states which, along with Me ...
in Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
; intergrades with ''pacificus'' in San Diego County
San Diego County (), officially the County of San Diego, is a county in the southwestern corner of the U.S. state of California. As of the 2020 census, the population was 3,298,634, making it California's second-most populous county and the fi ...
, if not elsewhere; vagrant individuals of ''saturatus'' and the Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
population, which look similar to intergrades, also seem to occur in its range. Resident all-year.[ This race is likely synonymous with ''melanocercus''.][
:A pale dusky buff form with indistinct barring, especially on the underside. Darker individuals tend to have a deeper ]fulvous
Fulvous is a colour, sometimes described as dull orange, brownish-yellow or tawny; it can also be likened to a variation of buff, beige or butterscotch. As an adjective it is used in the names of many species of birds, and occasionally other an ...
base to their upper sides. Humeral area is umber in color and the feathers of the feet are white and usually unmarked.[ A small race, it averages slightly larger in wing length than ''pacificus'' but weighs less on average. The wing chord length is , averaging , in males and , averaging , in females. Body mass ranges from , averaging , in males and from , averaging , in females. In both sexes, tail length is and bill length is .][
* Yucatán great horned owl (''Bubo virginianus mayensis'')
:Endemic to the southern two-thirds of the ]Yucatán Peninsula
The Yucatán Peninsula (, also , ; es, Península de Yucatán ) is a large peninsula in southeastern Mexico and adjacent portions of Belize and Guatemala. The peninsula extends towards the northeast, separating the Gulf of Mexico to the north ...
. Resident all-year.
:A medium-pale form, fairly similar to ''pallescens'' in both hue and ventral markings. Going on linear measurements, ''B. v. mayensis'' is smaller than all North American horned owls, even the smallish ''pallescens'', and is only slightly larger at median than the following race.[ This race has wing chord and tail lengths of and in males and and in females. In both sexes, the bill length is and tarsal length is .][
* Baja California great horned owl (''Bubo virginianus elachistus'')
:Southern ]Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
, Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
. Resident all-year.
:Similar in color to ''pacificus'' but even darker and more heavily barred, like a miniaturized ''saturatus''. It is considerably (5–10%) smaller than ''pacificus'' linearly; some size overlap does occur though. On average, it is the smallest known subspecies. Males have a wing chord length of , tail length of and bill length of . A single female had a wing chord of and tail of .[
* Northeastern great horned owl (''Bubo virginianus heterocnemis'')
:Breeds in eastern Canada (northern ]Quebec
Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...
, Labrador
, nickname = "The Big Land"
, etymology =
, subdivision_type = Country
, subdivision_name = Canada
, subdivision_type1 = Province
, subdivision_name1 ...
, Newfoundland
Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...
). Its southern breeding range seems to be delineated by the Saint Lawrence River
The St. Lawrence River (french: Fleuve Saint-Laurent, ) is a large river in the middle latitudes of North America. Its headwaters begin flowing from Lake Ontario in a (roughly) northeasterly direction, into the Gulf of St. Lawrence, connectin ...
.[ In winter, this race may disperses southwards throughout ]Ontario
Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...
to as far as the Northeastern United States
The Northeastern United States, also referred to as the Northeast, the East Coast, or the American Northeast, is a geographic region of the United States. It is located on the Atlantic coast of North America, with Canada to its north, the Southe ...
. This subspecies may be synonymous with ''saturatus'', although it is distributed far to the east of that race. ''B. v. heterocnemis'' is surrounded by the much paler ''subarcticus'' to its west and quite differently marked ''virginianus'' to its south, the latter two overlap and possibly hybridize in some of the northeast.
:A fairly dark and grey, heavily barred form. Feet pale with dusky mottling. Going on median reported linear measurements (since body mass is unknown), this is the largest bodied subspecies on average. Males have a wing chord length of and females range from . In both sexes, the tail is and the bill is .[
* Rocky Mountains great horned owl (''Bubo virginianus pinorum'')
:The ]Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
population breeds south of the Snake River
The Snake River is a major river of the greater Pacific Northwest region in the United States. At long, it is the largest tributary of the Columbia River, in turn, the largest North American river that empties into the Pacific Ocean. The Snake ...
in Idaho
Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyom ...
south to Arizona
Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
, New Mexico
)
, population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano)
, seat = Santa Fe
, LargestCity = Albuquerque
, LargestMetro = Tiguex
, OfficialLang = None
, Languages = English, Spanish ( New Mexican), Navajo, Ker ...
, and the Guadalupe Mountains
The Guadalupe Mountains ( es, Sierra de Guadalupe) are a mountain range located in West Texas and southeastern New Mexico. The range includes the highest summit in Texas, Guadalupe Peak, , and the "signature peak" of West Texas, El Capitan, both ...
of Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
. Westwards, it is presumed to occur to the Modoc Plateau
__NOTOC__
The Modoc Plateau lies in the northeast corner of California as well as parts of Oregon and Nevada. Nearly of the Modoc National Forest are on the plateau between the Medicine Lake Highlands in the west and the Warner Mountains in the ...
and Mono Lake
Mono Lake ( ) is a saline soda lake in Mono County, California, formed at least 760,000 years ago as a terminal lake in an endorheic basin. The lack of an outlet causes high levels of salts to accumulate in the lake which make its water alk ...
of California. This race was included in the presumed subspecies ''occidentalis'', but was recently first described and named as a distinct subspecies and makes up the missing piece in the once-muddled distribution of great horned owls in the West and Rockies. Downslope movements into valleys occupied by ''pallescens'' might occur, but this needs study.
:A medium gray form, intermediate in coloring between ''saturatus'' and ''pallescens''. Moderately barred and tinged buff or ochraceous on the underside. Feet mottled. This is a largish race, wing chord lengths being inexplicably greater in males, at , than in females, at . Tail length can range from and a female weighed .[
]
Species identification
The combination of the species' bulk, prominent ear tufts and barred plumage distinguishes it through much of the range, but it may be easily confused with the lesser or Magellanic horned owl (''B. magellanicus''), which may overlap in range.[ The Magellanic horned owl was once considered a subspecies of the great horned, but is now almost universally considered a distinct species, as is supported by genetic materials, with the great horned being the ]paraspecies
A paraspecies (a paraphyletic species) is a species, living or fossil, that gave rise to one or more daughter species without itself becoming extinct. Geographically widespread species that have given rise to one or more daughter species as perip ...
.[ Overall coloration is similar, but the Magellanic is markedly smaller with smaller feet and a smaller head, with finer, but more numerous brownish bars on the underside, rather than the blotchy, irregular barring typical of great horned owls.][ Other eagle-owls may superficially be somewhat similar, but the species is generically ]allopatric
Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...
with the exception of wintering snowy owls. More tropical species with ear tufts, the stygian owl
The stygian owl (''Asio stygius'') is a medium-sized "typical owl" in subfamily Striginae. It is found in Mexico, parts of Central America, Cuba, Hispaniola, and 10 countries in South America.HBW and BirdLife International (2020) ''Handbook of ...
(''A. stygius'') and striped owl
The striped owl (''Asio clamator'') is a medium-sized owl with large ear tufts and a brownish-white facial disk rimmed with black. Its beak is black, and it has cinnamon-colored eyes. It has shorter, rounder wings than most of its close relative ...
(''A. clamator''), are much smaller.[ Other large owls lack ear tufts.][
]
Distribution and habitat
The breeding habitat of the great horned owl extends high into the subarctic
The subarctic zone is a region in the Northern Hemisphere immediately south of the true Arctic, north of humid continental regions and covering much of Alaska, Canada, Iceland, the north of Scandinavia, Siberia, and the Cairngorms. Generally, ...
of North America, where they are found up to the northwestern and southern Mackenzie Mountains
The Mackenzie Mountains are a Canadian mountain range forming part of the Yukon-Northwest Territories boundary between the Liard and Peel rivers. The range is named in honour of Canada's second prime minister, Alexander Mackenzie. Nahanni Nat ...
, Keewatin, Ontario, northern Manitoba
Manitoba ( ) is a Provinces and territories of Canada, province of Canada at the Centre of Canada, longitudinal centre of the country. It is Canada's Population of Canada by province and territory, fifth-most populous province, with a population o ...
, Fort Chimo
Kuujjuaq (; iu, ᑰᑦᔪᐊᖅ, i=no or iu, ᑰᔾᔪᐊᖅ, i=no, label=none, "Great River"), formerly known as and by other names, is a former Hudson's Bay Company outpost at the mouth of the Koksoak River on Ungava Bay that has become ...
in Ungava, Okak, Newfoundland and Labrador, Anticosti Island
; moe, Notiskuan; mic, Natigostec
, sobriquet =
, image_name = RiviereHuileAnticosti.jpg
, image_caption = Salmon fisherman on Rivière à l'Huile
, image_map ...
and Prince Edward Island
Prince Edward Island (PEI; ) is one of the thirteen Provinces and territories of Canada, provinces and territories of Canada. It is the smallest province in terms of land area and population, but the most densely populated. The island has seve ...
. They are distributed throughout most of North America and very spottily in Central America and then down into South America south to upland regions of Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
, Bolivia
, image_flag = Bandera de Bolivia (Estado).svg
, flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center
, flag_alt2 = 7 × 7 square p ...
and Peru
, image_flag = Flag of Peru.svg
, image_coat = Escudo nacional del Perú.svg
, other_symbol = Great Seal of the State
, other_symbol_type = Seal (emblem), National seal
, national_motto = "Fi ...
, before they give way to the Magellanic horned owl, which thence ranges all the way to Tierra del Fuego
Tierra del Fuego (, ; Spanish for "Land of the Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of the main island, Isla G ...
, the southern tip of the continent. It is absent or rare from southern Guatemala
Guatemala ( ; ), officially the Republic of Guatemala ( es, República de Guatemala, links=no), is a country in Central America. It is bordered to the north and west by Mexico; to the northeast by Belize and the Caribbean; to the east by H ...
, El Salvador
El Salvador (; , meaning " The Saviour"), officially the Republic of El Salvador ( es, República de El Salvador), is a country in Central America. It is bordered on the northeast by Honduras, on the northwest by Guatemala, and on the south b ...
, Nicaragua
Nicaragua (; ), officially the Republic of Nicaragua (), is the largest country in Central America, bordered by Honduras to the north, the Caribbean to the east, Costa Rica to the south, and the Pacific Ocean to the west. Managua is the cou ...
, and Costa Rica
Costa Rica (, ; ; literally "Rich Coast"), officially the Republic of Costa Rica ( es, República de Costa Rica), is a country in the Central American region of North America, bordered by Nicaragua to the north, the Caribbean Sea to the no ...
to Panama
Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Cos ...
(where only two records) in Central America and the mangrove forests of northwestern South America. The species is also absent from the West Indies
The West Indies is a subregion of North America, surrounded by the North Atlantic Ocean and the Caribbean Sea that includes 13 independent island countries and 18 dependencies and other territories in three major archipelagos: the Greater A ...
, the Haida Gwaii
Haida Gwaii (; hai, X̱aaydag̱a Gwaay.yaay / , literally "Islands of the Haida people") is an archipelago located between off the northern Pacific coast of Canada. The islands are separated from the mainland to the east by the shallow Heca ...
and almost all off-shore islands in the Americas, its ability to colonize islands apparently being considerably less than those of barn owls and short-eared owl
The short-eared owl (''Asio flammeus'') is a widespread grassland species in the family Strigidae. Owls belonging to genus ''Asio'' are known as the eared owls, as they have tufts of feathers resembling mammalian ears. These "ear" tufts may or ...
s. Since the division into two species, the great horned owl is the second most widely distributed owl in the Americas, just after the barn owl.[
The great horned owl is among the world's most adaptable owls or even bird species in terms of habitat. The great horned owl can take up residence in trees that border all manner of ]deciduous
In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, aft ...
, coniferous
Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All extant ...
, and mixed forests, tropical rainforest
Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equatori ...
s, pampa
The Pampas (from the qu, pampa, meaning "plain") are fertile South American low grasslands that cover more than and include the Argentine provinces of Buenos Aires, La Pampa, Santa Fe, Entre Ríos, and Córdoba; all of Uruguay; and Brazil ...
s, prairie
Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the ...
, mountainous areas, desert
A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About on ...
s, subarctic tundra
In physical geography, tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. The term ''tundra'' comes through Russian (') from the Kildin Sámi word (') meaning "uplands", "treeless moun ...
, rocky coasts, mangrove swamp
Mangrove forests, also called mangrove swamps, mangrove thickets or mangals, are productive wetlands that occur in coastal intertidal zones. Mangrove forests grow mainly at tropical and subtropical latitudes because mangroves cannot withstand fre ...
forests, and some urban area
An urban area, built-up area or urban agglomeration is a human settlement with a high population density and infrastructure of built environment. Urban areas are created through urbanization and are categorized by urban morphology as cities, t ...
s.[ It is less common in the more extreme areas of the Americas. In the Mojave and ]Sonora Desert
The Sonoran Desert ( es, Desierto de Sonora) is a desert in North America and ecoregion that covers the northwestern Mexican states of Sonora, Baja California, and Baja California Sur, as well as part of the southwestern United States (in Arizona ...
s, they are absent from the heart of the deserts and are only found on the vegetated or rocky fringes. Even in North America, they are rare in landscapes including more than 70% old-growth forest, such as the aspen
Aspen is a common name for certain tree species; some, but not all, are classified by botanists in the section ''Populus'', of the '' Populus'' genus.
Species
These species are called aspens:
*'' Populus adenopoda'' – Chinese aspen (Chin ...
forest of the Rockies.[ They have only been recorded a handful of times in true ]rainforest
Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfores ...
s such as the Amazon rainforest
The Amazon rainforest, Amazon jungle or ; es, Selva amazónica, , or usually ; french: Forêt amazonienne; nl, Amazoneregenwoud. In English, the names are sometimes capitalized further, as Amazon Rainforest, Amazon Forest, or Amazon Jungle. ...
.[ In the ]Appalachian Mountains
The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...
, they appear to use old-growth forest but in Arkansas
Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the Osage ...
are actually often found near temporary agricultural openings in the midst of large areas of woodland. Similarly in south-central Pennsylvania
Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...
, the owls use cropland and pasture more than deciduous and total forest cover, indicating preference for fragmented landscapes. In prairies, grasslands and deserts, they can successfully live year round as long as there are rocky canyons, steep gullies and/or wooded coulees with shade-giving trees to provide them shelter and nesting sites.
In mountainous areas of North America, they are usually absent above the tree line
The tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually cold temperatures, extreme snowp ...
, but great horned owls can be found up to in California and in the Rockies.[ In the Andean Mountains, on the other hand, they have adapted to being a true montane species, often found at least above sea level and are regularly recorded in treeless ]Puna grassland
The puna grassland ecoregion, of the montane grasslands and shrublands biome, is found in the central Andes Mountains of South America. It is considered one of the eight Natural Regions in Peru,Pulgar Vidal, Javier: Geografía del Perú; Las Oc ...
zones at in Ecuador
Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ''Eku ...
and Peru
, image_flag = Flag of Peru.svg
, image_coat = Escudo nacional del Perú.svg
, other_symbol = Great Seal of the State
, other_symbol_type = Seal (emblem), National seal
, national_motto = "Fi ...
. They are generally rare in non-tidal wetland habitat, and are replaced in the high Arctic tundra
In physical geography, tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. The term ''tundra'' comes through Russian (') from the Kildin Sámi word (') meaning "uplands", "treeless mou ...
by snowy owls.[ They prefer areas where open habitats, which they often hunt in, and woods, where they tend to roost and nest, are juxtaposed.] Thus lightly populated rural regions can be ideal. This species can occasionally be found in urban or suburban areas. However, they seem to prefer areas with less human activity and are most likely to be found in park-like settings in such developed areas, unlike eastern
Eastern may refer to:
Transportation
*China Eastern Airlines, a current Chinese airline based in Shanghai
*Eastern Air, former name of Zambia Skyways
*Eastern Air Lines, a defunct American airline that operated from 1926 to 1991
*Eastern Air Li ...
and western screech owl
The western screech owl (''Megascops kennicottii'') is a small owl native to North and Central America, closely related to the eastern screech owl. The scientific name commemorates the American naturalist Robert Kennicott.
Description
Length ...
s (''Megascops asio'' & ''M. kennicottii'') which may regularly occur in busy suburban settings. All mated great horned owls are permanent residents of their territories, but unmated and younger birds move freely in search of company and a territory, and leave regions with little food in winter.[
]
Behavior
In most aspects of their behavior, great horned owls are typical of owls and most birds of prey. From experimentally raising young owls in captivity, Paul L. Errington felt that they were a bird of "essentially low intelligence" that could only hunt when partially wild and instinctually driven by hunger to hunt whatever they first encounter. He showed captive birds that were provided strips of meat from hatching, rather than having to hunt or to simulate hunting to obtain food, had no capacity to hunt. On the contrary, William J. Baerg compared behaviorally his captive-raised great horned owls to parrot
Parrots, also known as psittacines (), are birds of the roughly 398 species in 92 genera comprising the order Psittaciformes (), found mostly in tropical and subtropical regions. The order is subdivided into three superfamilies: the Psittacoid ...
s, which are famously intelligent birds, although not as often playful "it knows its keeper and usually accepts whatever he wishes to do with a good deal of tolerance". Arthur C. Bent also noted the variability in temperaments of great horned owls to their handlers, some generally pleasant, though most are eventually aggressive.[ Most captive specimens, once mature, seem to resent attempts at contact and are often given to attacking their keepers. They will only follow cues when conditioned from an early age but rarely with the same level of success seen in some diurnal birds of prey trained for ]falconry
Falconry is the hunting of wild animals in their natural state and habitat by means of a trained bird of prey. Small animals are hunted; squirrels and rabbits often fall prey to these birds. Two traditional terms are used to describe a person ...
or entertainment, although this does not necessarily correlate with intelligence as posited by Errington.[ Carl D. Marti also disagrees with Errington's assessments, noting that their prey selection is not as "completely random as Errington suggested"; while "Great Horned Owls appeared to select their mammalian prey in general relation to the prey populations...]cottontail
Cottontail rabbits are the leporid species in the genus ''Sylvilagus'', found in the Americas. Most ''Sylvilagus'' species have stub tails with white undersides that show when they retreat, giving them their characteristic name. However, this ...
s, appeared to be selected as prey out of relation to their population status."[
Like most owls, the great horned owl makes great use of secrecy and stealth. Due to its natural-colored plumage, it is well camouflaged both while active at night and while roosting during the day. During the daytime it roosts usually in large trees (including snags & large hollows but usually thick branches) but may occasionally be in crevices or small caves in rocks or in dense shrubbery. ]Pine
A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanical Garden accep ...
and other coniferous trees
Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All extan ...
may be preferred where available since they are particularly dense and provide cover throughout the year. Typically, males have a favorite roosting site not far from the nest, sometimes used over successive years.[ While roosting, great horned owls may rest in the "tall-thin" position, where they sit as erect and hold themselves as slim as is possible. The kind of posture is well known as a further method of camouflage for other owls, like long-eared owls or great grey owls, especially if humans or other potential mammalian carnivores approach them. The Eurasian eagle owl rarely, if ever, assumes the tall-thin position.] Outside of the nesting season, great horned owls may roost wherever their foraging path ends at dawn.[ Generally great horned owls are active at night, although in some areas they may be active in the late afternoon or early morning. At dusk, the owl utters a few calls before flying to a more open sing-post, i.e. large bare branch or large rocks to deliver song. Normally several perches are used to mark occupied territory or to attract a female.][ Despite its camouflage and cryptic locations, this species can still sometimes be spotted on its daytime roosts, especially by ]American crow
The American crow (''Corvus brachyrhynchos'') is a large passerine bird species of the family Corvidae. It is a common bird found throughout much of North America. American crows are the New World counterpart to the carrion crow of Europe an ...
s (''Corvus brachyrhynchos''). Since owls are, next to red-tailed hawk
The red-tailed hawk (''Buteo jamaicensis'') is a bird of prey that breeds throughout most of North America, from the interior of Alaska and northern Canada to as far south as Panama and the West Indies. It is one of the most common members wit ...
s, perhaps the main predator of crows and their young, crows sometimes congregate from considerable distances to mob owls and caw angrily at them for hours on end. When the owls try to fly off to avoid this harassment, they are often followed by the corvids.
Territoriality and movements
Typically, great horned owls are highly sedentary, often capable of utilizing a single territory throughout their mature lives. Although some species such as snowy owls, northern saw-whet owl
The northern saw-whet owl (''Aegolius acadicus'') is a species of small owl in the family Strigidae. The species is native to North America. Saw-whet owls of the genus ''Aegolius'' are some of the smallest owl species in North America. They can ...
s, long-eared and short-eared owls are true migrants, most North American owls are not migratory and will generally show fidelity to a single territory year around.[ In great horned owls, mated pairs occupy territories year-round and long-term. Territories are established and maintained through hooting, with highest activity before egg-laying and second peak in autumn when juveniles disperse, and can range from an average of in ]Yukon
Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...
to an average of in Wyoming
Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...
.[
Most territorial defense is performed by males, but females frequently assist their partners in hooting contests with neighbors or intruders, even during incubation.][ On occasion, although territory borders may be successfully maintained via vocalizations alone without even seeing the competing owl, such confrontations may turn physical, with various levels of threats distinguished. The highest threat level involves the spreading of wings, bill-clapping, hissing, higher-pitched screams of longer duration, with general body poised to strike with its feet at intruder. If the intruder continues to press the confrontation, the defending owl will "hop" forward and strike it with feet, attempting to grasp and rake with claws.][
Territoriality appears to place a limit on the number of breeding pairs in a given area. Individuals prevented from establishing a territory live a silent existence as "floaters". Radio-telemetry revealed that such floaters concentrate along boundaries of established territories. At ]Kluane Lake
Kluane Lake is located in the southwest area of the Yukon. It is the largest lake contained entirely within Yukon at approximately , and long.
Kluane Lake is located approximately northwest of Haines Junction. The Alaska Highway follows most of ...
in Yukon
Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...
, incursions into neighboring territories were observed only twice—by females when a neighboring female had died or emigrated, suggesting that territorial defense may be sex-specific. At least four dead great horned owls in Kluane were apparently killed by others of their own species in territorial conflicts.[ Owls killed by other horned owls are sometimes cannibalized, although the origin of the killing may have been territorial aggression. Northern populations occasionally irrupt south during times of food shortage,] but there is no annual migration even at the northern limits of the great horned owl's range.[
]
Hunting behavior
Hunting tends to peak between 8:30 pm and midnight and then can resume from 4:30 am to sunrise. Hunting tends to be most prolonged during winter by virtue of prey being more scarce. However, great horned owls can learn to target certain prey during daylight in the afternoon when it is more vulnerable, such as eastern fox squirrels (''Sciurus niger'') while they're building their leaf nests and chuckawallas (''Sauromalus ater'') sunning themselves on desert rocks. Owls hunt mainly by watching from a snag, pole or other high perch. During hunting forays, they often fly about from perch to perch, stopping to survey for food at each, until they sense a prey item below. From such vantage points, owls dive down to the ground, often with wings folded, to ambush their prey.[ Effective maximum hunting distance of an owl from an elevated perch is .][ Due to their short but broad wings, great horned owls are ideally suited for low speed and maneuverability.][ Despite reports that they do not hunt on the wing,] they also sometimes hunt by flying low over openings on the ground, scanning below for prey activity.[ Great horned owls can fly at speeds of more than in level flight.][ Hunting flights are slow, often quartering low above the ground where prey is likely to occur in open country or open woodland. Brief hovering flight (for about 6–18 seconds) has been described, especially in windy areas. On occasion owls may actually walk on the ground in pursuit of small prey or, rarely, inside a chicken coop to prey on the fowl within.] Rodent
Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...
s and invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s may be caught on foot around the base of bushes, through grassy areas, and near culverts and other human structures in range and farm habitat.[ The great horned owl is generally a poor walker on the ground; it walks like a ]starling
Starlings are small to medium-sized passerine birds in the family Sturnidae. The Sturnidae are named for the genus ''Sturnus'', which in turn comes from the Latin word for starling, ''sturnus''. Many Asian species, particularly the larger ones, ...
, with a pronounced side-to-side gait. They have been known to wade into shallow water for aquatic prey, although this has been only rarely reported.[ Owls can snatch ]bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
s and some arboreal mammals directly from tree branches in a glide as well. The stiff feathering of their wings allows owls to produce minimal sound in flight while hunting.
Almost all prey are killed by crushing with the owl's feet or by incidentally stabbing of the talons, though some may be bitten about the face as well. Prey is swallowed whole when possible. When prey is swallowed whole, owls regurgitate pellets of bone and other non-digestible bits about 6 to 10 hours later, usually in the same location where the prey was consumed.[ Great horned owl pellets are dark gray or brown in color and very large, long and thick, and have been known to contain skulls up to in width inside them.] However, not all prey can be swallowed at once, and owls will also fly with prey to a perch and tear off pieces with their bill. Most dietary studies focus on pellets found under perches and around nests, since they provide a more complete picture of the diversity of prey consumed, but prey remains outside of pellets may provide clues to prey excluded from the pellets and a combination of both is recommended. Many large prey items are dismembered. Great horned owls may behead large prey before taking it to its nest or eating perch. The legs may also be removed, as may (in some bird prey) the wings. The great horned owl will also crush the bones of its prey to make it more compact for carrying. On occasion, the owls may return to the kill site to continue eating if the prey is too heavy to fly with after dismemberment.[ Many owls will accrue a cache of prey, especially those who are nesting. Caches must be at a safe location, usually the crotch of a tall tree. In northern regions, where large prey is prevalent, an owl may let uneaten food freeze and then thaw it out later using its own body heat.][ Hunting success seems to require fairly open understory, and experimental testing of microhabitat proved that open areas provided more hunting success on five species of rodent, with cloudy nights and denser bush foliage both decreasing success.
]
Prey and trophic ecology
Prey can vary greatly based on opportunity. According to one author, "Almost any living creature that walks, crawls, flies, or swims, except the large mammals, is the great horned owl's legitimate prey".[ In fact, the great horned owl has the most diverse prey profile of any raptor in the Americas.][ Over 500 species have been identified as great horned owl prey, with dozens more identified only to genus or general type (especially numerous ]invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s) and presumably several more unknown from their relatively little-studied populations in the Neotropic
The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone.
Definition
In bioge ...
s. Mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s (more than 200 species) and bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
s (nearly 300 species) make up the majority of their diet. Their diet in North America is made up of 87.6% mammals, 6.1% birds, 1.6% reptile
Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
s and amphibian
Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...
s with the remaining 4.7% being made up by insects, other assorted invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s and fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
.[ Estimated mass of individual prey for the owls has ranged from as little as to as much as ] Most prey is in the range of (shrew
Shrews (family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to different fa ...
s) to (jackrabbit
Hares and jackrabbits are mammals belonging to the genus ''Lepus''. They are herbivores, and live solitarily or in pairs. They nest in slight depressions called forms, and their young are able to fend for themselves shortly after birth. The gen ...
s). A single owl requires about of food per day and can subsist on a large kill over several days. Despite the great diversity of prey taken by these predators, in most of the continental United States from the East to the Midwest as well as Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
and Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
, great horned owls largely live off just a handful of prey species: three species of lagomorph
The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families: the Leporidae (hares and rabbits) and the Ochotonidae (pikas). The name of the order is derived from the Ancient Greek ''lagos'' (λαγ ...
: the eastern cottontail
The eastern cottontail (''Sylvilagus floridanus'') is a New World cottontail rabbit, a member of the family Leporidae. It is the most common rabbit species in North America.
Distribution
The eastern cottontail can be found in meadows and shrubb ...
(''Sylvilagus floridanus''), the snowshoe hare
The snowshoe hare (''Lepus americanus''), also called the varying hare or snowshoe rabbit, is a species of hare found in North America. It has the name "snowshoe" because of the large size of its hind feet. The animal's feet prevent it from sink ...
(''Lepus americanus'') and the black-tailed jackrabbit
The black-tailed jackrabbit (''Lepus californicus''), also known as the American desert hare, is a common hare of the western United States and Mexico, where it is found at elevations from sea level up to . Reaching a length around , and a ...
(''Lepus californicus''); two species of New World mice: the white-footed mouse
The white-footed mouse (''Peromyscus leucopus'') is a rodent native to North America from Ontario, Quebec, Labrador, and the Maritime Provinces (excluding the island of Newfoundland) to the southwestern United States and Mexico. In the Maritimes, ...
and the North American deermouse (''Peromyscus leucopus & maniculatus''); approximately three species of vole
Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of lo ...
: the meadow
A meadow ( ) is an open habitat, or field, vegetated by grasses, herbs, and other non-woody plants. Trees or shrubs may sparsely populate meadows, as long as these areas maintain an open character. Meadows may be naturally occurring or artifi ...
, prairie
Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the ...
and woodland vole
The woodland vole (''Microtus pinetorum'') is a small vole found in eastern North America. It is also known as the pine vole.
Characteristics
The woodland vole has a head and body length ranging between with a short tail. Its weight ranges be ...
s (''Microtus pennsylvanicus, ochrogaster & pinetorum''); and one introduced pest, the brown rat.[
]
Rodents
Small rodent
Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...
s form the great majority of great horned owl prey by number. Weighing a mere and on average, the nine species of New World mice in ''Peromyscus'' and eight species voles in ''Microtus'' recorded in the diet would appear to be overly small to be as important as they are to a predatory bird of this size. The prominence of these genera is undoubtedly due to the abundance of both genera in the wooded edge habitats frequented by great horned owls. It is estimated that a family of owls with two offspring would need to take about a half dozen (voles) to a dozen (mice) of these rodents every night to satisfy their dietary requirements but apparently the accessibility and abundance of these foods is irresistible as their numeric dominance is indisputable.[ By winter in areas that hold heavy snow, '']Peromyscus
''Peromyscus'' is a genus of rodents. They are commonly referred to as deer mice or deermice, not to be confused with the chevrotain or "mouse deer". They are New World mice only distantly related to the common house and laboratory mouse, ''Mu ...
'' mice often come to outnumber the voles in the diet since the mice tend to travel over the surface of the snow while the voles make tunnels underneath the snow.[ In fact, a healthy family of great horned owls can decimate a colony of field rats, thus potentially performing a key role in controlling a highly destructive pest.][ Great horned owls living in the timbered fringes of garbage or refuse dumps may subsist mostly on rats.][
In the ]Rockies
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
, California, the Southwestern United States
The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona, New Mexico, and adjacent portions of California, Colorado, Ne ...
and northern Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
, the diversity of this species' diet rises, in sync with the diversity of rodents. Especially important, from Colorado
Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...
to Washington state
Washington (), officially the State of Washington, is a state in the Pacific Northwest region of the Western United States. Named for George Washington—the first U.S. president—the state was formed from the western part of the Washington ...
is the northern pocket gopher (''Thomomys talpoides''), although assorted other pocket gophers (''Geomys
The genus ''Geomys'' contains 12 species of pocket gophersSearch results for "''Geomys''" on thASM Mammal Diversity Database often collectively referred to as the eastern pocket gophers. Like all pocket gophers, members of this genus are fossori ...
, Cratogeomys
''Cratogeomys'' is a genus of rodent
Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of al ...
, Zygogeomys
The Michoacan pocket gopher (''Zygogeomys trichopus'') is a species of rodent in the family Geomyidae. It is monotypic within the genus ''Zygogeomys''. It is endemic to Mexico where its natural habitat is temperate, high-altitude forests. Its nu ...
, Pappogeomys
Buller's pocket gopher (''Pappogeomys bulleri'') is a species of gopher that is endemic to Mexico. It is monotypic within the genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil or ...
'' and other '' Thomomys'' ssp.) are readily taken. While the northern weighs from , other pocket gophers hunted average from in mass. From Washington
Washington commonly refers to:
* Washington (state), United States
* Washington, D.C., the capital of the United States
** A metonym for the federal government of the United States
** Washington metropolitan area, the metropolitan area centered o ...
to Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
a very important food is the pocket mice
Perognathinae is a subfamily of rodents consisting of two genera of pocket mice. Most species live in complex burrows within the deserts and grasslands of western North America, They feed mostly on seeds and other plant parts, which they carry i ...
, primarily the Great Basin pocket mouse (''Perognathus parvus''). While the Great Basin species is a relative giant at , other hunted pocket mice (which may include both ''Perognathus
''Perognathus'' is a genus of pocket mouse. Like other members of their family they are more closely related to pocket gophers than to true mice.
Characteristics
The silky pocket mice are small animals with soft pelage, long tails, and small ...
'' and ''Chaetodipus
''Chaetodipus'' is a genus of pocket mouse containing 17 species endemic to the United States and Mexico. Like other members of their family such as pocket mice in the genus ''Perognathus'', they are more closely related to pocket gophers than ...
'' ssp.) can average nearly as light as . In East Texas
East Texas is a broadly defined cultural, geographic, and ecological region in the eastern part of the U.S. state of Texas that comprises most of 41 counties. It is primarily divided into Northeast and Southeast Texas. Most of the region consi ...
, the hispid cotton rat
The hispid cotton rat (''Sigmodon hispidus'') is a rodent species long thought to occur in parts of South America, Central America, and southern North America. However, recent taxonomic revisions, based on mitochondrial DNA sequence data, have ...
(''Sigmodon hispidus'') is the most commonly recorded prey species. The same species constituted 75% by number of a small sampling in Oklahoma
Oklahoma (; Choctaw language, Choctaw: ; chr, ᎣᎧᎳᎰᎹ, ''Okalahoma'' ) is a U.S. state, state in the South Central United States, South Central region of the United States, bordered by Texas on the south and west, Kansas on the nor ...
. In semi-desert and other arid habitats, kangaroo rat
Kangaroo rats, small mostly nocturnal rodents of genus ''Dipodomys'', are native to arid areas of western North America. The common name derives from their bipedal form. They hop in a manner similar to the much larger kangaroo, but developed thi ...
s become increasingly important prey, ten species have been reported in the diet but most prominently the Ord's and Merriam's kangaroo rat
Merriam's kangaroo rat (''Dipodomys merriami'') is a species of rodent in the family Heteromyidae. The species name commemorates Clinton Hart Merriam. It is found in the Upper and Lower Sonoran life zones of the southwestern United States, Baja ...
s (''Dipodomys ordii & merriami''), both being widespread, numerous and relatively diminutive (at ). Eight known larger species of kangaroo rats, including the giant kangaroo rat
The giant kangaroo rat (''Dipodomys ingens'') is an endangered species of heteromyid rodent endemic to California.
Description
The giant kangaroo rat, is the largest of over 20 species of kangaroo rats, which are small members of the rodent f ...
(''Dipodomys ingens'') averaging at , are also taken.
The squirrel
Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrels. Squ ...
s, including ground squirrel
Ground squirrels are members of the squirrel family of rodents ( Sciuridae), which generally live on or in the ground, rather than trees. The term is most often used for the medium-sized ground squirrels, as the larger ones are more commonly known ...
s, marmot
Marmots are large ground squirrels in the genus ''Marmota'', with 15 species living in Asia, Europe, and North America. These herbivores are active during the summer, when they can often be found in groups, but are not seen during the winter, w ...
s (''Marmota''), prairie dog
Prairie dogs (genus ''Cynomys'') are herbivorous burrowing ground squirrels native to the grasslands of North America. Within the genus are five species: black-tailed, white-tailed, Gunnison's, Utah, and Mexican prairie dogs. In Mexico, p ...
s (''Cynomys''), chipmunk
Chipmunks are small, striped rodents of the family Sciuridae. Chipmunks are found in North America, with the exception of the Siberian chipmunk which is found primarily in Asia.
Taxonomy and systematics
Chipmunks may be classified either as ...
s and tree squirrel
Tree squirrels are the members of the squirrel family (Sciuridae) commonly just referred to as "squirrels." They include more than 100 arboreal species native to all continents except Antarctica and Oceania.
They do not form a single natural, o ...
s, are diurnal and so are largely unavailable to great horned owls as prey. Occasionally though, one will be caught from their leaf nest, nest hole or burrow entrance first thing in the morning or in the late afternoon and approximately 35 species have been successfully predated by these owls. In general larger sized than other rodent families, the species hunting range from the gray-collared chipmunk (''Tamias cinereicollis'') to the hoary marmot
The hoary marmot (''Marmota caligata'') is a species of marmot that inhabits the mountains of northwest North America. Hoary marmots live near the tree line on slopes with grasses and forbs to eat and rocky areas for cover.
It is the largest Nor ...
(''Marmota caligata''); thus, squirrels can be provide a very fulfilling meal.[ An even larger rodent is sometimes attacked as prey by great horned owls, the ]North American porcupine
The North American porcupine (''Erethizon dorsatum''), also known as the Canadian porcupine, is a large quill-covered rodent in the New World porcupine family. It is the second largest rodent in North America, after the North American beaver ('' ...
(''Erethizon dorsatum''), in which average adults range from . This has been determined from owls who have porcupine quills imbedded in them, sometimes resulting in death. On occasion, they are successful in killing porcupine, even adults as determined by the size of the quills left behind and prey remains at bloodied kill sites.[ Other rodents recorded as secondary prey in North America include ]flying squirrels
Flying squirrels (scientifically known as Pteromyini or Petauristini) are a tribe of 50 species of squirrels in the family Sciuridae. Despite their name, they are not in fact capable of full flight in the same way as birds or bats, but they ar ...
(''Glaucomys'' ssp.), the golden mouse
The golden mouse (''Ochrotomys nuttalli'') is a species of New World mouse. It is usually 5–8 inches (12–25 cm) in body length, and has a soft pelage that ranges from golden-brownish to burnt orange in color. The genus name comes ...
(''Ochrotomys nuttalli''), red-backed voles & bog lemmings (''Myodes'' & ''Synaptomys'' ssp.), the muskrat
The muskrat (''Ondatra zibethicus'') is a medium-sized semiaquatic rodent native to North America and an introduced species in parts of Europe, Asia, and South America. The muskrat is found in wetlands over a wide range of climates and habitat ...
(''Ondatra zibethicus''), the northern grasshopper mouse
The northern grasshopper mouse (''Onychomys leucogaster'') is a North American carnivorous rodent of the family Cricetidae. It ranges over much of the western part of the continent, from southern Saskatchewan and central Washington to Tamaulipas ...
(''Onychomys leucogaster''), the northern pygmy mouse (''Baiomys taylori'') and jumping mice (''Zapus'' & ''Napaeozapus'' ssp.).[
]
Lagomorphs
Although generally no match for rodents in sheer quantity of individuals, in terms of prey biomass, the most significant prey of North American great horned owls are hare
Hares and jackrabbits are mammals belonging to the genus ''Lepus''. They are herbivores, and live solitarily or in pairs. They nest in slight depressions called forms, and their young are able to fend for themselves shortly after birth. The ge ...
s and rabbit
Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (which also contains the hares) of the order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' includes the European rabbit speci ...
s. About a dozen lagomorphs species are known to be hunted by the owl, from the relatively tiny pygmy rabbit
The pygmy rabbit (''Brachylagus idahoensis'') is a rabbit species native to the United States. It is also the only native rabbit species in North America to dig its own burrow. The pygmy rabbit differs significantly from species within either the ...
to several hare
Hares and jackrabbits are mammals belonging to the genus ''Lepus''. They are herbivores, and live solitarily or in pairs. They nest in slight depressions called forms, and their young are able to fend for themselves shortly after birth. The ge ...
s weighing more than . Two hare species, the black-tailed jackrabbit
The black-tailed jackrabbit (''Lepus californicus''), also known as the American desert hare, is a common hare of the western United States and Mexico, where it is found at elevations from sea level up to . Reaching a length around , and a ...
and snowshoe hare, are so important to the owls as a food source that the local owl populations sharply rise and fall in sync with the hares' cyclical population trends. With adult weights of in adult cottontails, in snowshoe hares and in black-tailed jackrabbits, these species are overall the largest regular prey for this species.[ In ]Utah
Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
, where great horned owls are dependent on the jackrabbits, average brood size rose from 2 at jackrabbit population lows to 3.3 when the jackrabbits were at their peak. At the peak of population cycle, jackrabbits accounted for 90.2% and desert cottontail
The desert cottontail (''Sylvilagus audubonii''), also known as Audubon's cottontail, is a New World cottontail rabbit, and a member of the family Leporidae. Unlike the European rabbit (''Oryctolagus cuniculus''), they do not form social burrow s ...
s (''Sylvilagus audubonii'') for another 8.7% of prey biomass. In the short-grass prairie of Colorado
Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...
, mountain cottontail
The mountain cottontail or Nuttall's cottontail (''Sylvilagus nuttallii'') is a species of mammal in the family Leporidae. It is found in Canada and the United States.
Description
The mountain cottontail is a small rabbit but its size is rel ...
(''Sylvilagus nuttallii'') and black-tailed jackrabbits predominated in October to December, making up 42.9% by number (and nearly all the biomass), thence dropping to 9.3% by number in April, while voles rose to 32.2% peak in May, down to a minimum of 10.2% by number in June.[ Further north in Colorado, in the absence of jackrabbits, the mountain cottontails falls to third place by number (12.9%) behind the northern pocket gopher (36.5%) and prairie vole (24.7%) but still dominates the biomass, making up about half.] In central Utah
Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
, the lagomorphs (black-tailed jackrabbit/desert cottontail) and Ord's kangaroo rat each made up 39% of the food by number, respectively.[ The mountain cottontail dominates the biomass of prey in the Sierran foothills of California, making up 61.1% of the biomass, although are numerically secondary to desert woodrat.][ Remarkably, in the Morley Nelson Snake River Birds of Prey National Conservation Area of ]Idaho
Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyom ...
, individual rodents (1159 counted) were more than 10 times more numerous than lagomorphs (114 counted) by quantity and yet the jackrabbit and mountain cottontail still made up approximately half of the biomass. The dependence on lagomorphs also extends into Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
, as in Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
about a quarter of identified prey was black-tailed jackrabbit and either desert or the larger Mexican cottontail
The Mexican cottontail (''Sylvilagus cunicularius'') is a species of cottontail rabbit in the family Leporidae. It is endemic to Mexico where its natural habitats are temperate forests, subtropical or tropical dry forests and pastureland.
Taxono ...
(''Sylvilagus cunicularius''). In the northern boreal forest
Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic and Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by coniferous forests consisting mostly of pines, spruces, ...
, great horned owls are even more dependent on the snowshoe hare. At the peak of the 10 year hare cycle, snowshoe hares were by far the largest component of both summer and winter diets (77–81% and 90–99%, respectively, in Alberta
Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...
; 83–86% and 75–98%, respectively, in Yukon
Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...
). At the lowest point of the hare's cycle, summer diets consisted of only 0–16% snowshoe hare in Alberta and 12.7% in Yukon. When hares were scarce, great horned owls in these regions fed mostly on large rodent
Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...
s, mice and voles, grouse
Grouse are a group of birds from the order Galliformes, in the family Phasianidae. Grouse are presently assigned to the tribe Tetraonini (formerly the subfamily Tetraoninae and the family Tetraonidae), a classification supported by mitochondr ...
and duck
Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family. Divided among several subfamilies, they are a form t ...
s. Because fewer of these alternative prey species are available in boreal forest during winter, owls had to emigrate or suffer high mortalities if they stayed. In Alberta
Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...
, the local population of great horned owls can increase threefold from hare population lows to peaks. The dependency on the snowshoe hare by the great horned owl extends into Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
as well.
Other mammals
Other mammals are taken readily as well. From both the tropics and the United States, several species of opossum may be taken, down to the size of the tiny dwarf fat-tailed mouse opossum
The dwarf fat-tailed mouse opossum (''Thylamys velutinus''), also known as the velvety fat-tailed opossum is an opossum species from South America. It is endemic to Brazil, where it is found in cerrado and caatinga habitats. Its head-and-body len ...
(''Thylamys velutinus''). In Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
, white-eared opossum
The white-eared opossum (''Didelphis albiventris''), known as the timbu in Brazil and comadreja overa in Argentina, is an opossum species found in Argentina, Bolivia, Brazil, Paraguay, and Uruguay. It is a terrestrial and, sometimes, arboreal a ...
(''Didelphis albiventris'') were found in 12% of pellets, but all specimens appeared to be juveniles each weighing about . Quite differently, in Pennsylvania
Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...
, Virginia opossum
The Virginia opossum (''Didelphis virginiana''), also known as the North American opossum, is the only opossum living north of Mexico, its range extending south into Central America. It is the northernmost marsupial in the world. In the United S ...
(''Didelphis virginianus'') made up 6% by number of prey but due to their large size (approximately ) and that all specimens were adults, they occupied the highest percentage of biomass of any species in a wide study from that state. At least eight species of shrew
Shrews (family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to different fa ...
s are taken by opportunity and make up the smallest mammalian prey taken by great horned owls, as specimens of least shrew
The North American least shrew (''Cryptotis parvus'') is one of the smallest mammals, growing to be only up to 3 inches long. It has a long pointed snout and a tail never more than twice the length of its hind foot. The dense fur coat is e ...
(''Cryptotis parva'') or masked shrew
The cinereus shrew or masked shrew (''Sorex cinereus'') is a small shrew found in Alaska, Canada, and the northern United States. This is the most widely distributed shrew in North America, where it is also known as the common shrew.
Descriptio ...
(''Sorex cinereus'') have had an estimated weight of only .[ One of the more regularly taken shrews, though, is the larger ]northern short-tailed shrew
The northern short-tailed shrew (''Blarina brevicauda'') is the largest shrew in the genus ''Blarina'', and occurs in the northeastern region of North America. It is a semifossorial, highly active, and voracious insectivore and is present in a v ...
(''Blarina brevicauda''), which was represented in more than 2% of pellets in the Upper Midwest
The Upper Midwest is a region in the northern portion of the U.S. Census Bureau's Midwestern United States. It is largely a sub-region of the Midwest. Although the exact boundaries are not uniformly agreed-upon, the region is defined as referring ...
.[ ]Mole
Mole (or Molé) may refer to:
Animals
* Mole (animal) or "true mole", mammals in the family Talpidae, found in Eurasia and North America
* Golden moles, southern African mammals in the family Chrysochloridae, similar to but unrelated to Talpida ...
s, of at least four or five species, are also widely but lightly reported as prey.[ Remnants of ]armadillo
Armadillos (meaning "little armored ones" in Spanish) are New World placental mammals in the order Cingulata. The Chlamyphoridae and Dasypodidae are the only surviving families in the order, which is part of the superorder Xenarthra, along wi ...
, presumably nine-banded armadillo
The nine-banded armadillo (''Dasypus novemcinctus''), also known as the nine-banded long-nosed armadillo or common long-nosed armadillo, is a mammal found in North, Central, and South America, making it the most widespread of the armadillos. It ...
(''Dasypus novemcinctus''), have been found around owl nests in the south.[ 11 species of bat are known to be hunted by great horned owls.] One pellet in Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
was found to be composed entirely of Mexican free-tailed bat
The Mexican free-tailed bat or Brazilian free-tailed bat (''Tadarida brasiliensis'') is a medium-sized bat native to the Americas, so named because its tail can be almost half its total length and is not attached to its uropatagium. It has been ...
s (''Tadarida brasiliensis''). Smaller species of mammalian carnivore, such as ringtail
The ringtail (''Bassariscus astutus'') is a mammal of the raccoon family native to arid regions of North America. It is widely distributed and well adapted to disturbed areas. It has been legally trapped for its fur. It is listed as Least Co ...
(''Bassariscus astutus''), American mink
The American mink (''Neogale vison'') is a semiaquatic species of mustelid native to North America, though human intervention has expanded its range to many parts of Europe, Asia and South America. Because of range expansion, the American mink i ...
(''Neogale vison''), black-footed ferret (''Mustela nigripes'') and various other small mustelid
The Mustelidae (; from Latin ''mustela'', weasel) are a family of carnivorous mammals, including weasels, badgers, otters, ferrets, martens, minks and wolverines, among others. Mustelids () are a diverse group and form the largest family in ...
s (''Mustela'' ssp.), are sometimes taken as prey.[ Prey in the form of ]canids
Canidae (; from Latin, ''canis'', " dog") is a biological family of dog-like carnivorans, colloquially referred to as dogs, and constitutes a clade. A member of this family is also called a canid (). There are three subfamilies found within ...
, like fox
Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or ''brush'').
Twelve sp ...
es or coyote
The coyote (''Canis latrans'') is a species of canis, canine native to North America. It is smaller than its close relative, the wolf, and slightly smaller than the closely related eastern wolf and red wolf. It fills much of the same ecologica ...
s (''Canis latrans'') are often juveniles presumably snatched from the mouths of dens by night. Kit and swift fox
The swift fox (''Vulpes velox'') is a small light orange-tan fox around the size of a domestic cat found in the western grasslands of North America, such as Montana, Colorado, New Mexico, Kansas, Oklahoma and Texas. It also lives in southern Ma ...
es of up to adult size may taken.[ Surprisingly, at least two cases of a great horned owl preying on an adult ]raccoon
The raccoon ( or , ''Procyon lotor''), sometimes called the common raccoon to distinguish it from other species, is a mammal native to North America. It is the largest of the procyonid family, having a body length of , and a body weight of ...
(''Procyon lotor'') have been reported. One instance of an owl taking a bobcat
The bobcat (''Lynx rufus''), also known as the red lynx, is a medium-sized cat native to North America. It ranges from southern Canada through most of the contiguous United States to Oaxaca in Mexico. It is listed as Least Concern on the IUC ...
(''Lynx rufus'') as prey was also reportedly observed.[ In one case, a great horned owl was the likely killer of an adult female ]fisher
Fisher is an archaic term for a fisherman, revived as gender-neutral.
Fisher, Fishers or The Fisher may also refer to:
Places
Australia
*Division of Fisher, an electoral district in the Australian House of Representatives, in Queensland
*Elect ...
(''Martes pennanti''), though young ones are typically taken. Occasionally, domestic carnivores are also prey. A few cases of young or small dog
The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
s (''Canis lupus familiaris'') and several of juvenile and adult cat
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
s (''Felis silvestris catus'') being killed by great horned owls have been reported.[ The most infamous predatory association amongst relatively larger carnivores is that with skunks. Due to their poor sense of smell, great horned owls are the only predators to routinely attack these bold mammals with impunity. All six skunk species found in North America are reported as prey, including adult striped skunks (''Mephitis mephitis''), which can be three times as heavy as the attacking owl.][ In one single nest, the remains of 57 striped skunks were found.] Due to the proclivity of skunk predation, great horned owls nests frequently smell strongly of skunk and occasionally stink so powerfully of skunk that they leave the smell at kill sites or on prey remains.
Birds
After mammals, birds rank as the next most important general prey group. Birds are usually considerably secondary in the diet but outnumber the mammals in the diet by diversity, as more than 250 species have been killed in North America alone. Statistically, the most significant avian prey seems to be galliforms
Galliformes is an order (biology), order of heavy-bodied ground-feeding birds that includes turkey (bird), turkeys, chickens, Old World quail, quail, and other landfowl. Gallinaceous birds, as they are called, are important in their ecosystems ...
, of which they are known to have preyed on 23 species, basically consisting of all of the native species found in the United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
.[ In the ]Upper Midwest
The Upper Midwest is a region in the northern portion of the U.S. Census Bureau's Midwestern United States. It is largely a sub-region of the Midwest. Although the exact boundaries are not uniformly agreed-upon, the region is defined as referring ...
, the ring-necked pheasant
The common pheasant (''Phasianus colchicus'') is a bird in the pheasant family (Phasianidae). The genus name comes from Latin ''phasianus'', "pheasant". The species name ''colchicus'' is Latin for "of Colchis" (modern day Georgia), a country on ...
(''Phasianus colchicus'') and northern bobwhite
The northern bobwhite (''Colinus virginianus''), also known as the Virginia quail or (in its home range) bobwhite quail, is a ground-dwelling bird native to Canada, the United States, Mexico, and Cuba, with introduced populations elsewhere in th ...
(''Colinus virginianus'') were the fifth and sixth (out of 124 identified species) most significant prey species in 4838 pellets.[ Errington characterized the predatory pressure exerted on bobwhites by great horned owls as "light but continuous pressure", which may be considered characteristic of the species' hunting of all galliforms.] Usually coveys of quail are partially protected by spending the night roosting communally in dense thickets but should a hunting owl be able to track down the communal roost, losses can be fairly heavy until the roost relocates.[ Similarly, owls may track down sleeping ]grouse
Grouse are a group of birds from the order Galliformes, in the family Phasianidae. Grouse are presently assigned to the tribe Tetraonini (formerly the subfamily Tetraoninae and the family Tetraonidae), a classification supported by mitochondr ...
, which also roost in vegetation but more openly than quail. Some grouse, such as greater prairie chicken
The greater prairie chicken or pinnated grouse (''Tympanuchus cupido''), sometimes called a boomer,Friederici, Peter (July 20, 1989)"The Last Prairie Chickens" ''Chicago Reader''. Retrieved August 27, 2014.(Chinese 中文:帕艺明彩大凤 ...
(''Tympanuchus cupido''), sharp-tailed grouse
The sharp-tailed grouse (''Tympanuchus phasianellus''), also known as the sharptail or fire grouse, is a medium-sized prairie grouse. One of three species in the genus '' Tympanuchus'', the sharp-tailed grouse is found throughout Alaska, much of ...
(''Tympanuchus phasianellus'') and greater sage-grouse
The greater sage-grouse (''Centrocercus urophasianus''), also known as the sagehen, is the largest grouse (a type of bird) in North America. Its range is sagebrush country in the western United States and southern Alberta and Saskatchewan, Canad ...
(''Centrocercus urophasianus''), may also been vulnerable to great horned owls while displaying conspicuously in openings on a lek
Lek or LEK may refer to:
* Lek mating, mating in a lek, a type of animal territory in which males of a species gather
* Albanian lek, the currency of Albania
* Lek (magazine), a Norwegian softcore pornographic magazine
* Lek (pharmaceutical comp ...
first thing in the morning. In the boreal forest, especially in years where the snowshoe hare experiences population decreases, great horned owls prey fairly heavily (approximately 25% of biomass) on ruffed grouse
The ruffed grouse (''Bonasa umbellus'') is a medium-sized grouse occurring in forests from the Appalachian Mountains across Canada to Alaska. It is the most widely distributed game bird in North America. It is non-migratory. It is the only specie ...
(''Bonasa umbellus'') and spruce grouse
The spruce grouse (''Canachites canadensis''), also known as Canada grouse, spruce hen or fool hen, is a medium-sized grouse closely associated with the coniferous boreal forests or taiga of North America. It is the only member of the genus ''C ...
(''Falcipennis canadensis''), enough so in the earlier bird to possibly contribute to population reductions.[ Larger species of galliform are not immune to predation either. On Protection Island in ]Washington state
Washington (), officially the State of Washington, is a state in the Pacific Northwest region of the Western United States. Named for George Washington—the first U.S. president—the state was formed from the western part of the Washington ...
, introduced common peafowl
The Indian peafowl (''Pavo cristatus''), also known as the common peafowl, and blue peafowl, is a peafowl species native to the Indian subcontinent. It has been introduced to many other countries. Male peafowl are referred to as peacocks, and ...
(''Pavo cristatus'') are an important prey item. The wild turkey
The wild turkey (''Meleagris gallopavo'') is an Upland game bird, upland ground bird native to North America, one of two extant species of Turkey (bird), turkey and the heaviest member of the order Galliformes. It is the ancestor to the domestic ...
(''Meleagris gallopavo''), on average between the sexes, is probably the largest bird the great horned owl hunts in which they kill adults. Both full-grown wild turkeys and adult domestic turkeys[ have been hunted and killed. Under normal circumstances, ]domestic chicken
The chicken (''Gallus gallus domesticus'') is a domestication, domesticated junglefowl species, with attributes of wild species such as the grey junglefowl, grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster ...
(''Gallus gallus domesticus'') will be ignored in favor of wild prey. On occasion, individual owls, especially inexperienced juveniles, will become habitual fowl killers. These errant owls mainly hunt chickens, though will also take domestic guineafowl
Guineafowl (; sometimes called "pet speckled hens" or "original fowl") are birds of the family Numididae in the order Galliformes. They are endemic to Africa and rank among the oldest of the gallinaceous birds. Phylogenetically, they branched o ...
, turkeys and anything else available.[ In general, chickens kept in locked cages with enclosed tops overnight are safe from great horned owls; not so chickens left free range or in open enclosures.][
While galliforms are widely reported, the few cases where great horned owls locally turn to birds as the primary food source over mammals, these may often be local responses to the abundance of breeding ]water bird
A water bird, alternatively waterbird or aquatic bird, is a bird that lives on or around water. In some definitions, the term ''water bird'' is especially applied to birds in freshwater ecosystems, although others make no distinction from seabi ...
s or concentrations of roosting water birds, since they tend to roost in relatively open spots. They have been known to predate more than 110 different species of assorted water bird.[ In prairie wetlands of ]North Dakota
North Dakota () is a U.S. state in the Upper Midwest, named after the Native Americans in the United States, indigenous Dakota people, Dakota Sioux. North Dakota is bordered by the Canadian provinces of Saskatchewan and Manitoba to the north a ...
, avian prey, primarily represented by duck
Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family. Divided among several subfamilies, they are a form t ...
s and the American coot
The American coot (''Fulica americana''), also known as a mud hen or pouldeau, is a bird of the family Rallidae. Though commonly mistaken for ducks, American coots are only distantly related to ducks, belonging to a separate order. Unlike the w ...
(''Fulica americana'') came to represent 65% by number and 83% by biomass of the diet of the local owls, also including secondarily grebe
Grebes () are aquatic diving birds in the order Podicipediformes . Grebes are widely distributed freshwater birds, with some species also found in marine habitats during migration and winter. Some flightless species exist as well, most notably ...
s, smaller rails
Rail or rails may refer to:
Rail transport
*Rail transport and related matters
*Rail (rail transport) or railway lines, the running surface of a railway
Arts and media Film
* ''Rails'' (film), a 1929 Italian film by Mario Camerini
* ''Rail'' ( ...
and shorebird
245px, A flock of Dunlins and Red knots">Red_knot.html" ;"title="Dunlins and Red knot">Dunlins and Red knots
Waders or shorebirds are birds of the order Charadriiformes commonly found wikt:wade#Etymology 1, wading along shorelines and mudflat ...
s as well as upland-based species like grey partridge
The grey partridge (''Perdix perdix''), also known as the gray-legged partridge, English partridge, Hungarian partridge, or hun, is a gamebird in the pheasant family Phasianidae of the order Galliformes, gallinaceous birds. The scientific name ...
(''Perdix perdix''), sharp-tailed grouse
The sharp-tailed grouse (''Tympanuchus phasianellus''), also known as the sharptail or fire grouse, is a medium-sized prairie grouse. One of three species in the genus '' Tympanuchus'', the sharp-tailed grouse is found throughout Alaska, much of ...
and passerine
A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped'), which includes more than half of all bird species. Sometimes known as perching birds, passerines are distinguished from other orders of birds by t ...
s. 77% of the ducks in that study were juveniles, the largest duck being a male mallard
The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa, and has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Arge ...
(''Anas platyrhnychos'') weighing approximately , but nearly all the coots were adults.[ On Protection Island, ]Washington
Washington commonly refers to:
* Washington (state), United States
* Washington, D.C., the capital of the United States
** A metonym for the federal government of the United States
** Washington metropolitan area, the metropolitan area centered o ...
, where they are no native land mammals, rhinoceros auklets (''Cerorhinca monocerata''), both adults and nestlings, were the most numerous prey, present in 93% of 120 pellets.[ Species as large as adult ]Canada geese
The Canada goose (''Branta canadensis''), or Canadian goose, is a large wild goose with a black head and neck, white cheeks, white under its chin, and a brown body. It is native to the arctic and temperate regions of North America, and it is o ...
, snow goose
The snow goose (''Anser caerulescens'') is a species of goose native to North America. Both white and dark morphs exist, the latter often known as blue goose. Its name derives from the typically white plumage. The species was previously placed ...
[ and ]great blue heron
The great blue heron (''Ardea herodias'') is a large wading bird in the heron family Ardeidae, common near the shores of open water and in wetlands over most of North America and Central America, as well as the Caribbean and the Galápagos ...
s[ have been successfully killed. The nestlings of even larger species like ]trumpeter swan
The trumpeter swan (''Cygnus buccinator'') is a species of swan found in North America. The heaviest living bird native to North America, it is also the largest extant species of waterfowl, with a wingspan of 185 to 250 cm (6 ft 2 in to 8 ft 2 ...
s (''Cygnus buccinator''), American white pelicans (''Pelecanus eryhtrorhynchos''), brown pelican
The brown pelican (''Pelecanus occidentalis'') is a bird of the pelican family, Pelecanidae, one of three species found in the Americas and one of two that feed by diving into water. It is found on the Atlantic Coast from New Jersey to the mout ...
s (''Pelecanus occidentalis'') and sandhill crane
The sandhill crane (''Antigone canadensis'') is a species of large crane of North America and extreme northeastern Siberia. The common name of this bird refers to habitat like that at the Platte River, on the edge of Nebraska's Sandhills on t ...
s (''Grus canadensis'') have also been killed by these owls.
Other assorted birds are taken seemingly at random opportunity. The predatory effect of this species on other raptorial birds, which is often considerable, is explored in the following section. In Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
, it was found in a small study that birds overall outnumbered mammals in pellets, although most were not determined to species and the ones that were shown a tremendously diverse assemblage of birds with no obvious dietary preference.[ Although not usually numerically significant, 86 species of ]passerine
A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped'), which includes more than half of all bird species. Sometimes known as perching birds, passerines are distinguished from other orders of birds by t ...
have been taken by great horned owls. Members from most North American families are known as prey, although among smaller types such as chickadee
The chickadees are a group of North American birds in the tit family included in the genus '' Poecile''. Species found in North America are referred to as chickadees, while other species in the genus are called tits.
They are small-sized bird ...
s, warbler
Various Passeriformes (perching birds) are commonly referred to as warblers. They are not necessarily closely related to one another, but share some characteristics, such as being fairly small, vocal, and insectivorous.
Sylvioid warblers
Th ...
s, sparrows, cardinals
Cardinal or The Cardinal may refer to:
Animals
* Cardinal (bird) or Cardinalidae, a family of North and South American birds
**''Cardinalis'', genus of cardinal in the family Cardinalidae
**''Cardinalis cardinalis'', or northern cardinal, the ...
, wrens and most tyrant flycatcher
The tyrant flycatchers (Tyrannidae) are a family of passerine birds which occur throughout North and South America. They are considered the largest family of birds known to exist in the world, with more than 400 species. They are the most dive ...
s only a few species from each have been recorded. Nonetheless, an occasionally unlucky migrant or local breeder is sometimes snatched.[ Fledgling songbirds are regularly taken in spring and summer.][ The smallest avian prey known for great horned owls are the ]blue-grey gnatcatcher
The blue-gray gnatcatcher or blue-grey gnatcatcher (''Polioptila caerulea'') is a very small songbird native to North America. Description
It is in length, 6.3 in (16 cm) in wingspan, and weighing only . Adult males are blue-gray on the upperpa ...
(''Polioptila caerulea'') and the ruby-crowned kinglet
The ruby-crowned kinglet (''Corthylio calendula'') is a very small passerine bird found throughout North America. It is a member of the kinglet family. The bird has olive-green plumage with two white wing bars and a white eye-ring. Males have a ...
(''Regulus calendula'').[ Somewhat larger bodied families are more prominent, i.e. the ]corvid
Corvidae is a Cosmopolitan distribution, cosmopolitan family (biology), family of oscine passerine birds that contains the crows, ravens, rook (bird), rooks, jackdaws, jays, magpies, treepies, choughs, and nutcracker (bird), nutcrackers. In coll ...
s (14 species) and icterids (14 species) and, secondarily, the kingbird
''Tyrannus'' is a genus of small passerine birds of the tyrant flycatcher family native to the Americas. The majority are named as kingbirds. Description
They prefer semi-open or open areas. These birds wait on an exposed perch and then catch i ...
s (''Tyrannus'' ssp.), thrushes
The thrushes are a passerine bird family, Turdidae, with a worldwide distribution. The family was once much larger before biologists reclassified the former subfamily Saxicolinae, which includes the chats and European robins, as Old World flyca ...
, mimid
__NOTOC__
The mimids are the New World family of passerine birds, Mimidae, that includes thrashers, mockingbirds, tremblers, and the New World catbirds. As their name (Latin for "mimic") suggests, these birds are notable for their vocalization, ...
s and European starling
The common starling or European starling (''Sturnus vulgaris''), also known simply as the starling in Great Britain and Ireland, is a medium-sized passerine bird in the starling family, Sturnidae. It is about long and has glossy black plumage ...
(''Sturnus vulgaris'').[ This is likely due to the fact that the larger passerines usually roost in relatively open spots and have larger, more conspicuous nests. ]Crow
A crow is a bird of the genus '' Corvus'', or more broadly a synonym for all of ''Corvus''. Crows are generally black in colour. The word "crow" is used as part of the common name of many species. The related term "raven" is not pinned scientifica ...
s and ravens tend to be grabbed off of their communal roosts by night.[
]
Other prey
The great horned owl rarely misses an opportunity to hunt reptile
Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
s and amphibian
Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...
s. However, lizard
Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...
s are largely unavailable as prey due to their typically diurnal periods of activity.[ However, some snakes are partially or largely nocturnal, and more than a dozen species are hunted in North America. Snakes hunted range from small, innocuous ]garter snake
Garter snake is a common name for generally harmless, small to medium-sized snakes belonging to the genus ''Thamnophis'' in the family Colubridae. Native to North and Central America, species in the genus ''Thamnophis'' can be found from the ...
s (''Thamnophis'' ssp.) and night snake
The night snake (''Hypsiglena torquata'') is a species of rear-fanged colubrid. It is found from British Columbia, Canada through the western United States to Mexico.
Subspecies previously recognized within ''H. torquata''
*'' Hypsiglena torq ...
s (''Hypsiglena torquata'') to venomous species like cottonmouth
''Agkistrodon piscivorus'' is a species of pit viper in the subfamily Crotalinae of the family Viperidae. It is one of the world's few semiaquatic vipers (along with the Florida cottonmouth), and is native to the southeastern United States. As ...
s (''Agkistrodon piscivorus'') and prairie rattlesnake Prairie rattlesnake may refer to:
* '' Crotalus viridis'', a.k.a. the plains rattlesnake, a venomous pitviper species native to the western United States, southwestern Canada, and northern Mexico.
* ''Sistrurus catenatus
The massasauga (''Sistr ...
s (''Crotalus virdis'') and formidable, large species like common king snakes (''Lampropeltis getula'') and black rat snake Black rat snake may refer to:
*'' Pantherophis alleghaniensis'', the eastern ratsnake
* '' Pantherophis spiloides'', the central ratsnake
*''Pantherophis obsoletus
''Pantherophis obsoletus'', also known commonly as the western rat snake, black ...
s (''Pantherophis obsoletus''), which in mature specimens can rival the owl in mass and sheer predatory power.[ The capture of the hatchlings of very large reptiles such as ]loggerhead turtle
The loggerhead sea turtle (''Caretta caretta'') is a species of oceanic turtle distributed throughout the world. It is a marine reptile, belonging to the family Cheloniidae. The average loggerhead measures around in carapace length when full ...
s (''Caretta caretta'') and American alligator
The American alligator (''Alligator mississippiensis''), sometimes referred to colloquially as a gator or common alligator, is a large crocodilian reptile native to the Southeastern United States. It is one of the two extant species in the g ...
s (''Alligator mississippiensis'') by great horned owls has been reported, in both cases likely when the baby reptiles are attempting to make their way to the security of water.[ On rare occasion, ]salamander
Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten ...
s, frog
A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...
s and toad
Toad is a common name for certain frogs, especially of the family Bufonidae, that are characterized by dry, leathery skin, short legs, and large bumps covering the parotoid glands.
A distinction between frogs and toads is not made in scientif ...
s are reported as prey. On rare occasions, fish are taken including goldfish
The goldfish (''Carassius auratus'') is a freshwater fish in the family Cyprinidae of order Cypriniformes. It is commonly kept as a pet in indoor aquariums, and is one of the most popular aquarium fish. Goldfish released into the wild have ...
(''Carassius auratus''), bluegill
The bluegill (''Lepomis macrochirus''), sometimes referred to as "bream", "brim", "sunny", or "copper nose" as is common in Texas, is a species of North American freshwater fish, native to and commonly found in streams, rivers, lakes, ponds and ...
(''Lepomis macrochirus''), bullheads (''Ameiurus'' ssp.), other catfish
Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive, ...
, suckers, sunfish, eel
Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 19 families, 111 genera, and about 800 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...
s and dace and chub.[ Many types of invertebrates are recorded as prey. These include mainly insects, but also ]crayfish
Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, mu ...
, crab
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...
s, spider
Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...
s, scorpion
Scorpions are predatory arachnids of the order Scorpiones. They have eight legs, and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always end ...
s and worm
Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always).
Worms vary in size from microscopic to over in length for marine polychaete wor ...
s. The occasionally invertebrate prey taken largely consists of common, large insects such as various beetle
Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...
s, crickets
Crickets are orthopteran insects which are related to bush crickets, and, more distantly, to grasshoppers. In older literature, such as Imms,Imms AD, rev. Richards OW & Davies RG (1970) ''A General Textbook of Entomology'' 9th Ed. Methuen 8 ...
, grasshopper
Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago.
Grasshopp ...
s, water bug Waterbug or water bug can refer to any of several things:
True bugs
* The true water bugs (Nepomorpha), including such insects as giant water bugs, creeping water bugs and backswimmers
* Various other aquatic true bugs, known collectively as wate ...
s and katydids, some of which the great horned owl has even reportedly caught via "hawking", i.e. swooping at on the wing.[ In some cases, the content of insects in great horned owl pellets may actually be due to the owls eating other birds which have freshly eaten insects in their own stomachs.][ It is commonly believed that routine insectivory in great horned owls is mainly restricted to inexperienced young owls too unskilled to graduate to larger prey yet. It is clearly inefficient for owls of this size to attempt to raise young on a diet of foods as small as insects.][ Although rare, ]carrion
Carrion () is the decaying flesh of dead animals, including human flesh.
Overview
Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures, c ...
-feeding has been recorded in great horned owls, especially ones wintering in Canada and other northern areas during harsh weather. Road kills are sometimes opportunistically eaten. A case of an owl scavenging a white-tailed deer
The white-tailed deer (''Odocoileus virginianus''), also known as the whitetail or Virginia deer, is a medium-sized deer native to North America, Central America, and South America as far south as Peru and Bolivia. It has also been introduced t ...
(''Odocoileus virginianus'') carcass, ultimately tearing off the deer's leg, was captured on a motion capture video camera set out to film wildlife.
Urban vs rural diet
Studies comparing the diets of rural and urban great horned owls have identified that the most abundant rodent prey in their environment fulfils the majority of their diet. A study of food niche overlap between closely nested barn and great horned owls living in rural north-eastern Oregon identified voles as by far the most common prey. In southwestern British Columbia
British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
, Townsend's vole
Townsend's vole (''Microtus townsendii'') is a species of rodent in the family Cricetidae, the sister species of '' M. canicaudus''. It is found in temperate grasslands of British Columbia in Canada and in the states of Washington and Oregon in t ...
s were the most common prey species, while consumption of rats increased as the nesting location became more urban and rats replaced voles as the most abundant and stable food source. A similar focus on rats was found in populations in urban parks in Seattle
Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015, it is the largest city in both the state of Washington and the Pacific Northwest regio ...
. Although a stable and highly abundant food source, a diet consisting of primarily rats can be harmful to urban great horned owls due to bioaccumulation
Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance at a rate faster than that at which the substance is lost or eliminated ...
of rodenticide
Rodenticides are chemicals made and sold for the purpose of killing rodents. While commonly referred to as "rat poison", rodenticides are also used to kill mice, squirrels, woodchucks, chipmunks, porcupines, nutria, beavers, and voles. Despi ...
s.
Interspecific predatory relationships
Due to their very broad dietary habits, the great horned owls share their prey with many other predators, including avian, mammalian and reptilian ones. Almost every study comparing the diets of North American owls illustrates the considerable overlap in the dietary selection of these species, as all species, besides the primarily insectivorous varieties, rely on many of the same small rodent species for most of their diet, extending from the small northern saw-whet owl and eastern screech owl
The eastern screech owl (''Megascops asio'') or eastern screech-owl, is a small typical owl, owl that is relatively common in Eastern North America, from Mexico to Canada. This species is native to most wooded environments of its distribution, a ...
to the great horned and great grey owls.[
In a long-term study of a block of ]Michigan
Michigan () is a state in the Great Lakes region of the upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the 10th-largest state by population, the 11th-largest by area, and the ...
, all nine species of accipitrid, falcon and owl that stayed to breed there were found to be primarily dependent on the same two rodent genera, the meadow vole
The eastern meadow vole (''Microtus pennsylvanicus''), sometimes called the field mouse or meadow mouse, is a North American vole found in eastern Canada and the United States. Its range extends farther south along the Atlantic coast.
The west ...
and the two common ''Peromyscus
''Peromyscus'' is a genus of rodents. They are commonly referred to as deer mice or deermice, not to be confused with the chevrotain or "mouse deer". They are New World mice only distantly related to the common house and laboratory mouse, ''Mu ...
'' species.[ In the ]Great Basin
The Great Basin is the largest area of contiguous endorheic basin, endorheic watersheds, those with no outlets, in North America. It spans nearly all of Nevada, much of Utah, and portions of California, Idaho, Oregon, Wyoming, and Baja California ...
, the owls share black-tailed jackrabbit and desert cottontail
The desert cottontail (''Sylvilagus audubonii''), also known as Audubon's cottontail, is a New World cottontail rabbit, and a member of the family Leporidae. Unlike the European rabbit (''Oryctolagus cuniculus''), they do not form social burrow s ...
as the primary prey with golden eagles, red-tailed hawks and ferruginous hawk
The ferruginous hawk, (''Buteo regalis''), is a large bird of prey and belongs to the broad-winged buteo hawks. An old colloquial name is ferrugineous rough-leg, due to its similarity to the closely related rough-legged hawk (''B. lagopus'').
...
s (''Buteo regalis''); all four species had diets with more than 90% of the biomass is made up of those lagomorphs. Of these, the great horned owl and golden eagle were able to nest most closely to one another because they had the most strongly dissimilar periods of activity.[ In California, when compared to the local red-tailed hawks and ]western diamondback rattlesnake
The western diamondback rattlesnake or Texas diamond-backWright AH, Wright AA. (1957). ''Handbook of Snakes''. Comstock Publishing Associates. (7th printing, 1985). . (''Crotalus atrox'') is a rattlesnake species and member of the viper family, ...
s (''Crotalus atrox''), the diets were most similar in that by number about 15-20% of all three species' diets depended on cottontail
Cottontail rabbits are the leporid species in the genus ''Sylvilagus'', found in the Americas. Most ''Sylvilagus'' species have stub tails with white undersides that show when they retreat, giving them their characteristic name. However, this ...
s, but the largest portion was made up of ground squirrel
Ground squirrels are members of the squirrel family of rodents ( Sciuridae), which generally live on or in the ground, rather than trees. The term is most often used for the medium-sized ground squirrels, as the larger ones are more commonly known ...
s in the hawk and the rattlesnake and desert woodrats and other assorted rodent
Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...
s in the great horned owl.[ In the ]boreal forests
Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic and Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by coniferous forests consisting mostly of pines, spruces ...
, the great horned owl's prolificacy as a snowshoe hare
The snowshoe hare (''Lepus americanus''), also called the varying hare or snowshoe rabbit, is a species of hare found in North America. It has the name "snowshoe" because of the large size of its hind feet. The animal's feet prevent it from sink ...
hunter places it second only to the Canada lynx
The Canada lynx (''Lynx canadensis''), or Canadian lynx, is a medium-sized North American lynx that ranges across Alaska, Canada, and northern areas of the contiguous United States. It is characterized by its long, dense fur, triangular ears ...
(''Lynx canadensis'') among all predators. Although locally dependent on the hares as their main food, northern goshawk
The northern goshawk (; ''Accipiter gentilis'') is a species of medium-large bird of prey, raptor in the Family (biology), family Accipitridae, a family which also includes other extant diurnal raptors, such as eagles, buzzards and harrier (bird) ...
s (''Accipiter gentilis''), red-tailed hawks and golden eagles apparently do not have as large of an impact on the hares, nor do mammalian carnivore generalists that also kill many hares, like the fisher
Fisher is an archaic term for a fisherman, revived as gender-neutral.
Fisher, Fishers or The Fisher may also refer to:
Places
Australia
*Division of Fisher, an electoral district in the Australian House of Representatives, in Queensland
*Elect ...
, bobcat
The bobcat (''Lynx rufus''), also known as the red lynx, is a medium-sized cat native to North America. It ranges from southern Canada through most of the contiguous United States to Oaxaca in Mexico. It is listed as Least Concern on the IUC ...
, wolverine
The wolverine (), (''Gulo gulo''; ''Gulo'' is Latin for "gluttony, glutton"), also referred to as the glutton, carcajou, or quickhatch (from East Cree, ''kwiihkwahaacheew''), is the largest land-dwelling species of the family Mustelidae. It is ...
(''Gulo gulo''), coyote
The coyote (''Canis latrans'') is a species of canis, canine native to North America. It is smaller than its close relative, the wolf, and slightly smaller than the closely related eastern wolf and red wolf. It fills much of the same ecologica ...
and larger varieties (i.e. wolves
The wolf (''Canis lupus''; plural, : wolves), also known as the gray wolf or grey wolf, is a large Canis, canine native to Eurasia and North America. More than thirty subspecies of Canis lupus, subspecies of ''Canis lupus'' have been reco ...
(''Canis lupus''), cougar
The cougar (''Puma concolor'') is a large Felidae, cat native to the Americas. Its Species distribution, range spans from the Canadian Yukon to the southern Andes in South America and is the most widespread of any large wild terrestrial mamm ...
s (''Puma concolor'') and bear
Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the Nor ...
s (''Ursus'' ssp.)).[
The relationship between great horned owls and other raptorial birds in its range is usually decidedly one-sided. While certain species, such as the red-tailed hawk and ]northern goshawk
The northern goshawk (; ''Accipiter gentilis'') is a species of medium-large bird of prey, raptor in the Family (biology), family Accipitridae, a family which also includes other extant diurnal raptors, such as eagles, buzzards and harrier (bird) ...
, might be seen as potential competition for the owls, most others seem to be regarded merely as prey by great horned owls. The great horned owl is both the most prolific and diverse predator in America of other birds of prey, with other accomplished raptor-hunters such as the goshawk and the golden eagle being more restricted in range, habitat and number in North America and thus having a more minor impact. All studies have found raptors are a small portion of this owl's diet but predation can be seriously detrimental for such prey, as raptors tend to be territorial and sparsely distributed as a rule and thus can be effectively decimated by a small number of losses.[ In the ]gray hawk
The gray hawk (''Buteo plagiatus'') or Mexican goshawk is a smallish Bird of prey, raptor found in open country and forest edges. It is sometimes placed in the genus ''Asturina'' as ''Asturina plagiata''. The species was split by the American Orn ...
(''Buteo plagiatus''), for example, in a study of one breeding block of Arizona
Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
, the owls were observed to visit nests nightly until all the nestlings were gone.
Raptorial birds in general tend to have large, conspicuous nests which may make them easier for a hunting owl to locate. The great horned owl gains an advantage by nesting earlier than any other raptor in its range (indeed any bird), as it is able to exploit the other raptors as food while in a more vulnerable state as their own nestlings have become well developed.[ On average, great horned owls begin nesting about three weeks before red-tailed hawks begin to build nests, although some raptors may locally breed as much as two months after the owls.][Dunstan, T. C., & Harrell, B. E. (1973). ''Spatio-temporal relationships between breeding red-tailed hawks and great horned owls in South Dakota''. Raptor Research, 7(2), 49–54.]
More so than diurnal varieties of raptor, fairly significant numbers of owls are hunted, as all species are to some extent nocturnal and thus their corresponding activity can attract the horned owl's unwanted attention. The extent of predation on other owls depends on the habitat preferences of the other species. Eastern and western screech owls may be most vulnerable since they prefer similar wooded edge habitat. In a block of Wisconsin
Wisconsin () is a state in the upper Midwestern United States. Wisconsin is the 25th-largest state by total area and the 20th-most populous. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake M ...
, great horned owls were responsible for the failure of 78% of eastern screech owl's nests.[ Long-eared owls and, to a lesser extent, barn owls tend to hunt in open, sparsely treed habitats more so than great horned owls, but since they may return to wooded spots for nesting purposes, they may be more vulnerable there. The long-eared owl and barn owls are often compared to the great horned owl as these medium-sized species often occur in abutting habitats and often hunt primarily the same vole and mice species, although the alternate prey of the great horned tends to be much larger, including the smaller owls themselves.][ In a pair of studies from ]Colorado
Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...
, the average weight of prey for long-eared owls was , for barn owl and for the great horned owl.[
Both young and adult great grey owls, despite their superficially superior size, are apparently hunted with impunity by great horned owls. In the boreal forests, both the northern hawk owl and great grey owl appear to be in greater danger of great horned owl predation in years where the snowshoe hare have low populations.][Duncan, J. R. 1987. ''Movement strategies, mortality, and behavior of radio-marked Great Gray Owls in southeastern Manitoba and northern Minnesota''. Pages 101-107 in Biology and conservation of northern forest owls: Symposium proceedings, February 3–7, Winnipeg, MB. (Nero, R. W., R. J. Clark, R. J. Knapton, and R. H. Hamre, Eds.) General Technical Report, RM-142. Fort Collins, CO: USDA, Forest Service, Rocky Mountain Forest and Range Experiment Station.] Great horned owls were the leading cause of mortality in juvenile spotted owls (30% of losses) and juvenile great grey owls (65% of losses).[ Less is known about relations with the snowy owl, which may compete with great horned owls for food while invading south for the winter. Anecdotally, both snowy and great horned owls have rarely been reported to dominate or even kill one another depending on the size and disposition of the individual owls, although the snowy's preference for more open areas again acts as something of a buffer. The snowy may be the one North American owl too formidable for the great horned owl to consider as prey.][
Whereas owls of any age are freely attacked by great horned owls whether nesting or not, when it comes to diurnal raptors, great horned owls are mainly a danger around the nest. They often hunt diurnal raptors when they come across their often relatively conspicuous active platform nests during hunting forays in spring and summer, taking numbers of both nestlings and brooding adults.][ Again, like owls, diurnal raptors are attacked depending on the relative similarity of their habitat preferences to the owl. ]Cooper's hawk
Cooper's hawk (''Accipiter cooperii'') is a medium-sized hawk native to the North American continent and found from southern Canada to Mexico. This species is a member of the genus ''Accipiter'', sometimes referred to as true hawks, which are f ...
s (''Accipiter cooperii'') and red-tailed hawks tend to be most vulnerable, as they prefer the same wooded edges frequented by great horned owls. Other diurnal raptors may be attracted to more enclosed wooded areas, such as sharp-shinned hawk
The sharp-shinned hawk (''Accipiter striatus'') is a small hawk, with males being the smallest hawks in the United States and Canada, but with the species averaging larger than some Neotropical realm, Neotropical species, such as the tiny hawk. ...
s (''Accipiter striatus'') or zone-tailed hawk
The zone-tailed hawk (''Buteo albonotatus'') is a medium-sized hawk of warm, dry parts of the Americas. It is somewhat similar in plumage and flight style to a common scavenger, the turkey vulture, and may benefit from being able to blend into g ...
s (''Buteo albonotatus''), or more open plain and meadow areas, such as Northern harrier
The northern harrier (''Circus hudsonius''), or ring-tailed hawk, is a bird of prey. It breeds throughout the northern parts of the northern hemisphere in Canada and the northernmost USA.
The northern harrier migrates to more southerly areas ...
s (''Circus hudsonius'') and ferruginous hawks, but this is almost never a total insurance against predation as all of these are recorded prey.[
In a study of ]red-shouldered hawk
The red-shouldered hawk (''Buteo lineatus'') is a medium-sized buteo. Its breeding range spans eastern North America and along the coast of California and northern to northeastern-central Mexico. It is a permanent resident throughout most of its ...
(''Buteo lineatus'') and broad-winged hawk
The broad-winged hawk (''Buteo platypterus'') is a medium-sized hawk of the genus ''Buteo''. During the summer, some subspecies are distributed over eastern North America, as far west as British Columbia and Texas; they then migrate south to wi ...
(''Buteo brachyurus'') breeding in New York, despite their nesting in deeper woods than those that host these owls, the main cause of nest failure was great horned owl predation.[ Similarly, the great horned owl was the primary cause of nesting failure for both desert-dwelling ]Harris's hawk
The Harris's hawk (''Parabuteo unicinctus''), formerly known as the bay-winged hawk, dusky hawk, and sometimes a wolf hawk, and known in Latin America as peuco, is a medium-large bird of prey that breeds from the southwestern United States south ...
s (''Parabuteo unicinctus'') and forest-dwelling northern goshawk
The northern goshawk (; ''Accipiter gentilis'') is a species of medium-large bird of prey, raptor in the Family (biology), family Accipitridae, a family which also includes other extant diurnal raptors, such as eagles, buzzards and harrier (bird) ...
in Arizona
Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
(39% and 40% of failures, respectively), wetland-inhabiting osprey
The osprey (''Pandion haliaetus''), , also called sea hawk, river hawk, and fish hawk, is a diurnal, fish-eating bird of prey with a cosmopolitan range. It is a large raptor reaching more than in length and across the wings. It is brown o ...
(''Pandion haliaetus'') in Delaware
Delaware ( ) is a state in the Mid-Atlantic region of the United States, bordering Maryland to its south and west; Pennsylvania to its north; and New Jersey and the Atlantic Ocean to its east. The state takes its name from the adjacent Del ...
(21% of failures) and peregrine falcon
The peregrine falcon (''Falco peregrinus''), also known as the peregrine, and historically as the duck hawk in North America, is a Cosmopolitan distribution, cosmopolitan bird of prey (Bird of prey, raptor) in the family (biology), family Falco ...
s (''Falco peregrinus'') in the Western United States
The Western United States (also called the American West, the Far West, and the West) is the region comprising the westernmost states of the United States. As American settlement in the U.S. expanded westward, the meaning of the term ''the Wes ...
(27% of failures). The fact that many of the nests great horned owls use are constructed by accipitrids may lead to localized conflicts, almost always to the detriment of the hawks rather than the owls. While the young of larger diurnal raptors are typically stolen in the night, great horned owls also readily kill large adult raptors both in and out of breeding seasons, including osprey
The osprey (''Pandion haliaetus''), , also called sea hawk, river hawk, and fish hawk, is a diurnal, fish-eating bird of prey with a cosmopolitan range. It is a large raptor reaching more than in length and across the wings. It is brown o ...
, northern goshawk
The northern goshawk (; ''Accipiter gentilis'') is a species of medium-large bird of prey, raptor in the Family (biology), family Accipitridae, a family which also includes other extant diurnal raptors, such as eagles, buzzards and harrier (bird) ...
and rough-legged buzzard
The rough-legged buzzard or rough-legged hawk (''Buteo lagopus'') is a medium-large bird of prey. It is found in Arctic and Subarctic regions of North America, Europe, and Russia during the breeding season and migrates south for the winter. It ...
.
Great horned owls are frequently mobbed by other birds. Most accipitrids will readily mob them, as will falcons. Hen harrier
The hen harrier (''Circus cyaneus'') is a bird of prey. It breeds in Eurasia. The term "hen harrier" refers to its former habit of preying on free-ranging fowl.
It migrates to more southerly areas in winter. Eurasian birds move to southern Eur ...
s, northern goshawk
The northern goshawk (; ''Accipiter gentilis'') is a species of medium-large bird of prey, raptor in the Family (biology), family Accipitridae, a family which also includes other extant diurnal raptors, such as eagles, buzzards and harrier (bird) ...
s, Cooper's hawk
Cooper's hawk (''Accipiter cooperii'') is a medium-sized hawk native to the North American continent and found from southern Canada to Mexico. This species is a member of the genus ''Accipiter'', sometimes referred to as true hawks, which are f ...
s, Harris's hawk
The Harris's hawk (''Parabuteo unicinctus''), formerly known as the bay-winged hawk, dusky hawk, and sometimes a wolf hawk, and known in Latin America as peuco, is a medium-large bird of prey that breeds from the southwestern United States south ...
s, red-tailed hawks, Swainson's hawk
Swainson's hawk (''Buteo swainsoni'') is a large bird species in the Accipitriformes order. This species was named after William Swainson, a British naturalist. It is colloquially known as the grasshopper hawk or locust hawk, as it is very fond ...
s, ferruginous hawk
The ferruginous hawk, (''Buteo regalis''), is a large bird of prey and belongs to the broad-winged buteo hawks. An old colloquial name is ferrugineous rough-leg, due to its similarity to the closely related rough-legged hawk (''B. lagopus'').
...
s, red-shouldered hawk
The red-shouldered hawk (''Buteo lineatus'') is a medium-sized buteo. Its breeding range spans eastern North America and along the coast of California and northern to northeastern-central Mexico. It is a permanent resident throughout most of its ...
s, American kestrel
The American kestrel (''Falco sparverius''), also called the sparrow hawk, is the smallest and most common falcon in North America. It has a roughly two-to-one range in size over subspecies and sex, varying in size from about the weight of ...
s, peregrine falcon
The peregrine falcon (''Falco peregrinus''), also known as the peregrine, and historically as the duck hawk in North America, is a Cosmopolitan distribution, cosmopolitan bird of prey (Bird of prey, raptor) in the family (biology), family Falco ...
s, prairie falcon
The prairie falcon (''Falco mexicanus'') is a medium-large sized falcon of western North America. It is about the size of a peregrine falcon or a crow, with an average length of 40 cm (16 in), wingspan of approximately 1 meter (40&nb ...
s (''Falco mexicanus'') and common raven
The common raven (''Corvus corax'') is a large all-black passerine bird. It is the most widely distributed of all corvids, found across the Northern Hemisphere. It is a raven known by many names at the subspecies level; there are at least ...
s (''Corvus corax'') are among the reported species who have been recorded diving on great horned owls when they discover them.[Rohner, C., Krebs, C. J., Hunter, D. B., & Currie, D. C. (2000). ''Roost site selection of great horned owls in relation to black fly activity: an anti-parasite behavior? '' The Condor, 102(4), 950-955.] In Arizona
Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
and Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
, they may be mobbed by Mexican jay
The Mexican jay (''Aphelocoma wollweberi'')
Etymology: ''Aphelocoma'', from Latinized Ancient Greek ''apheles-'' (from ἀφελής-) "simple" + Latin ''coma'' (from Greek ''kome'' κόμη) "hair", in reference to the lack of striped or banded ...
s and western scrub jay Western scrub jay has been split into the following species:
* California scrub jay, ''Aphelocoma californica''
* Woodhouse's scrub jay, ''Aphelocoma woodhouseii''
The island scrub jay
The island scrub jay (''Aphelocoma insularis''), also known ...
s (''Aphelocoma wollweberi & californica'') and western
Western may refer to:
Places
*Western, Nebraska, a village in the US
*Western, New York, a town in the US
*Western Creek, Tasmania, a locality in Australia
*Western Junction, Tasmania, a locality in Australia
*Western world, countries that id ...
and Cassin's kingbird
Cassin's kingbird (''Tyrannus vociferans'') is a large tyrant flycatcher native to western North America. The name of this bird commemorates the American ornithologist John Cassin.
Taxonomy
Cassin's kingbird was formally described in 1826 by En ...
s (''Tyrannus verticalis & vociferans''). In addition, there are several documented incidences of American crow
The American crow (''Corvus brachyrhynchos'') is a large passerine bird species of the family Corvidae. It is a common bird found throughout much of North America. American crows are the New World counterpart to the carrion crow of Europe an ...
s mobbing a great horned owl, in groups of dozens or even hundreds of crows.[ In response to mobbing, if the owl flies it alights to the nearest secluded spot. If an owl alights on ground or on exposed branch or ledge, it may respond to swooping and stooping flights of corvids and raptors with threat display and raising of its wings.][
]
Reproduction
Great horned owls are some of the earliest-breeding birds in North America, seemingly in part because of the lengthy nightfall at this time of year and additionally the competitive advantage it gives the owl over other raptors. In most of North America, courtship is from October to December and mates are chosen by December to January.[ This species was once thought to be strictly monogamous, but recent analysis indicates one male may mate with two females simultaneously, as was discovered for the first time in 2018 in Reno, Nevada. During courtship in late fall or early winter, the male attracts the attention of his mate by hooting emphatically while leaning over (with the tail folded or cocked) and puffing up his white throat to look like a ball.][ The white throat may serve as a visual stimulus in the low light conditions typical of when this owl courts.][ He often flies up and down on a perch, while approaching the potential mate. Eventually, he comes to approach the female and tries to rub his bill against hers while repeatedly bowing. If receptive, the female hoots back when the pair meet but is more subdued in both her hoot and display. The male may convince the female by bringing her freshly caught prey, which they will share.][ While males often hoot emphatically for about a month or six weeks towards the end of the year, the period where females also hoot is usually only a week to ten days.][ Pairs typically breed together year after year and may mate for life, although they associate with each other more loosely when their young become mostly independent.][ Pairs rekindling their reproductive relationship in the winter may perform a milder courtship to strengthen pair bonds before producing young.][
Males select nesting sites and bring the females' attention to them by flying to the nest and then stomping on it.][ Considering the owls' large size, nests with open access are preferred to those enclosed with surrounding branches. Like all owls, great horned owls do not build their own nest. Great horned owls tend to examine an area for an abandoned nest, generally from larger birds like hawks, and take over the nest for raising their own young. They nest in a wider variety of sites than any other North American bird.][ Many nests are in cavernous hollows of dead trees or their branches, and especially in southern states in large trees along the edge of old-growth lots.][ In mountainous or hilly areas, especially in canyons of the ]Southwest
The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each sepa ...
and Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
, cliff ledges, small caves, and other sheltered depressions may be used.[ Owls living in prairie country, in the absence of other animals' nests, riparian tree-hollows or man-made structures, will use boulders, buttes, railroad cuts, low bushes and even the bare ground as nest sites.][ Ground nests have also been recorded in the midst of tall grasses in ]Florida
Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
and in the midst of brushy spots on desert ground.[ Even the burrow entrances of ]American badger
The American badger (''Taxidea taxus'') is a North American badger similar in appearance to the European badger, although not closely related. It is found in the western, central, and northeastern United States, northern Mexico, and south-cent ...
and coyote
The coyote (''Canis latrans'') is a species of canis, canine native to North America. It is smaller than its close relative, the wolf, and slightly smaller than the closely related eastern wolf and red wolf. It fills much of the same ecologica ...
dens have reportedly been used as nests, in spite of the inherent risk of sharing space with such potentially dangerous co-inhabitants.[ Nesting behavior for the great horned owl appears to be more closely related to prey availability than it does to seasonal conditions. There has been some evidence that if prey availability is low enough then the species may forgo mating entirely for a season. Male and female owls of the species have been observed to help incubate the eggs once they have been laid on a nest.
Most tree nests used by great horned owls are constructed by other animals, often from a height of about off the ground. They often take over a nest used by some other large bird, sometimes adding feathers to line the nest but usually not much more. Allegedly there have some cases where the owls have reinforced a nest structure or appeared to have reconstructed a nest, but as a rule no owl species has ever been known to actually build a nest.][ Great horned owls in the Southwest may also use nests in ]cacti
A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Greek ...
, built by Harris's hawk
The Harris's hawk (''Parabuteo unicinctus''), formerly known as the bay-winged hawk, dusky hawk, and sometimes a wolf hawk, and known in Latin America as peuco, is a medium-large bird of prey that breeds from the southwestern United States south ...
and red-tailed hawk, as well as large hollows in cacti. The nests they use are often made by most larger types of acciptrids, from species as small as Cooper's hawk
Cooper's hawk (''Accipiter cooperii'') is a medium-sized hawk native to the North American continent and found from southern Canada to Mexico. This species is a member of the genus ''Accipiter'', sometimes referred to as true hawks, which are f ...
s to bald eagle
The bald eagle (''Haliaeetus leucocephalus'') is a bird of prey found in North America. A sea eagle, it has two known subspecies and forms a species pair with the white-tailed eagle (''Haliaeetus albicilla''), which occupies the same niche as ...
and golden eagle, though perhaps most often those of red-tailed hawks and other buteonines. Secondly in popularity are crow
A crow is a bird of the genus '' Corvus'', or more broadly a synonym for all of ''Corvus''. Crows are generally black in colour. The word "crow" is used as part of the common name of many species. The related term "raven" is not pinned scientifica ...
and raven (''Corvus'' ssp.) nests. Even Canada goose
The Canada goose (''Branta canadensis''), or Canadian goose, is a large wild goose with a black head and neck, white cheeks, white under its chin, and a brown body. It is native to the arctic and temperate regions of North America, and it is o ...
, black-crowned night heron (''Nycticorax nycticorax'') and great blue heron
The great blue heron (''Ardea herodias'') is a large wading bird in the heron family Ardeidae, common near the shores of open water and in wetlands over most of North America and Central America, as well as the Caribbean and the Galápagos ...
nests have been used, the latter sometimes right in the midst of an active heronry
A heronry, sometimes called a heron rookery, is a breeding ground for herons.
Notable heronries
Although their breeding territories are often on more protected small islands in lakes or retention ponds, herons breed in heronries (or also calle ...
. The leaf nests of squirrel
Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrels. Squ ...
s are also regularly used but in general great horned owls are partial to stick nests since they provide a much firmer, safer foundation.[
The stage at which eggs are laid is variable across North America. In ]Southern Florida
South Florida is the southernmost region of the U.S. state of Florida. It is one of Florida's three most commonly referred to directional regions; the other two are Central Florida and North Florida. South Florida is the southernmost part of th ...
, eggs may be laid as early as late November to as late as early January. In the southeast
The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each sepa ...
, from south Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
to Georgia
Georgia most commonly refers to:
* Georgia (country), a country in the Caucasus region of Eurasia
* Georgia (U.S. state), a state in the Southeast United States
Georgia may also refer to:
Places
Historical states and entities
* Related to the ...
, egg laying may begin from late December to early February. From Southern California
Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most po ...
to northern Louisiana
Louisiana , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is borde ...
, egg laying is from early February to late March. The largest swath of egg-laying owls from central California to South Carolina
)''Animis opibusque parati'' ( for, , Latin, Prepared in mind and resources, links=no)
, anthem = " Carolina";" South Carolina On My Mind"
, Former = Province of South Carolina
, seat = Columbia
, LargestCity = Charleston
, LargestMetro = ...
to as far north as Ohio
Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...
and is from late February to early April. In the Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
, Northwestern United States
The Northwestern United States, also known as the American Northwest or simply the Northwest, is an informal geographic region of the United States. The region consistently includes the states of Oregon, Washington, Idaho, Montana and Wyoming. ...
, northern New England
New England is a region comprising six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York to the west and by the Canadian provinces ...
and eastern Canada, egg laying is from early March to late April. In the rest of Canada and Alaska, egg laying may be from late March to early May.[ The latest known date of egg laying was in mid-June in ]Saskatchewan
Saskatchewan ( ; ) is a Provinces and territories of Canada, province in Western Canada, western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on t ...
and the Yukon Territory
Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...
. In northwestern Utah
Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
and north-central Alberta
Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...
, egg-laying can be 3–4 weeks earlier than usual when food is abundant and weather is favorable.[ For owls found in more tropical climates, the dates of the breeding season are somewhat undefined.][ There are usually 2 eggs per clutch, but clutches range in size from 1 to 6 eggs (over 3 is uncommon, over 4 is very rare), depending on environmental conditions. The average egg width is , the average length is and the average weight is , although mass could be slightly higher elsewhere because this figure is from ]Los Angeles County
Los Angeles County, officially the County of Los Angeles, and sometimes abbreviated as L.A. County, is the most populous county in the United States and in the U.S. state of California, with 9,861,224 residents estimated as of 2022. It is the ...
, CA where the owls are relatively small.[Turner, Jr., J. C. and L. McClanahan, Jr. 1981. ''Physiogenesis of endothermy and its relation to growth in the Great Horned Owl, Bubo virginianus''. Compilation of Biochemical Physiology, 68A:167-173.] The incubation period ranges from 28 to 37 days, averaging 33 days.[Hoffmeister, D. F. and H. W. Setzer. 1947. ''The postnatal development of two broods of Great Horned Owls (Bubo virginianus)''. University of Kansas Publishing Museum of Natural History, 1:157-173.] The female alone usually does all the incubation and rarely moves from the nest, while the male owl captures food and brings it to her, with the first nightly food delivery typically occurring soon after dark.[
The young weigh at birth on average and can gain about a day for the first four weeks of life, with typical weights in the range of by 25–29 days for males and females, respectively.][ When first hatched the young are covered in whitish gray down, with some brownish about the wings. Gradually the soft juvenal downy plumage comes through the down, being typically a cinnamon-buff color, but with variable hues predicting the eventual color of the mature owls. The extent of down gradually diminishes, developing mature-looking plumage by late summer, although many first year birds still have scattered bits of down into autumn. By late autumn, first-year birds look similar to adults but with a slightly warmer, reddish tinge, less well developed ear tufts and a smaller white throat patch.][ The nestling owls develop mostly in behavior between two weeks and two months of age, in which time they adapt the ability to defend themselves, grasp foods and climb. Vocally, the young are able to exert weak chips while still in the egg, developing into a raspy chirp shortly after hatching. The calls of the young increase rapidly in intensity, pitch and character, some juvenile males mimicking their father's hooting in fall but usually they conclude with various odd gurgling notes. The earliest competent hooting by juvenile owls is not until January.][ Young owls move onto nearby branches at 6 weeks and start to fly about a week later. However, the young are not usually competent fliers until they are about 10 to 12 weeks old.][ The age at which the young leave the nest is variable based on the abundance of food.]