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The northern hawk-owl or northern hawk owl (''Surnia ulula'') is a medium-sized
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 ...
of the northern latitudes. It is non-migratory and usually stays within its breeding range, though it sometimes irrupts southward. It is one of the few owls that is neither
nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...
nor
crepuscular In zoology, a crepuscular animal is one that is active primarily during the twilight period, being matutinal, vespertine, or both. This is distinguished from diurnal and nocturnal behavior, where an animal is active during the hours of dayli ...
, being active only during the day. This is the only living species in the
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
''Surnia'' of the family Strigidae, the "typical" owls (as opposed to
barn owls The barn owl (''Tyto alba'') is the most widely distributed species of owl in the world and one of the most widespread of all species of birds, being found almost everywhere except for the polar and desert regions, Asia north of the Himalaya ...
, Tytonidae). The species is sometimes called simply the hawk owl; however, many species of owls in the genus '' Ninox'' are also called "hawk owls".


Taxonomy

The northern hawk-owl was formally described by the Swedish naturalist
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, ...
in 1758 in the tenth edition of his ''
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 ...
'' under 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, bo ...
''Strix ulula''. The owl is now the only species placed in the genus ''Surnia'' that was introduced in 1805 by André Duméril. The
type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specim ...
was designated by
George Robert Gray George Robert Gray FRS (8 July 1808 – 6 May 1872) was an English zoologist and author, and head of the ornithological section of the British Museum, now the Natural History Museum, in London for forty-one years. He was the younger brother ...
in 1840 as the northern hawk-owl. The genus name is of unknown etymology and may simply have been invented by Duméril. The specific epithet ''ulula'' is Latin for a "screech owl". A
molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
study of the owls published in 2019 found that the northern hawk-owl is sister to a
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...
containing the pygmy owls in the genus ''Glaucidium''. Three
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 specie ...
are recognised: * ''S. u. tianschanica'' Smallbones, 1906 – central Asia to northern China and northern Mongolia * ''S. u. ulula'' (Linnaeus, 1758) – northern Eurasia * ''S. u. caparoch'' ( Müller, PLS, 1776) – northern North America


Description

Male northern hawk-owls are generally long and weigh about . Females are slightly bigger with a length of and a mass of about . Both male and female have similar wingspans of about . The northern hawk-owl plumage is relatively dark brown with an off-white spotting pattern on all
dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...
parts of the body with the exception of the back of the neck which boasts a black v-shaped pattern. The underbelly is generally white or off-white which continues to the toes with brown bands on the breast and stomach. It also has a long tail with brown banding. The northern hawk-owl has a smokey white face with a black border, a flat head, yellow eyes and a yellow curved beak.Duncan, James R. and Patricia A. Duncan. (1998
Northern Hawk-Owl (''Surnia ulula'')
The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: .
The northern hawk-owl has been said to resemble a hawk in appearance and in behavior. In North America, its appearance in flight is often considered similar to a
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 ...
(''Accipiter cooperii''). It has been suggested that this may be because the hawk-owl may partially fill an important diurnal niche similar to that of day hunters such as hawks.


Vocalization

Various calls are used by the different sexes in different situations. When attracting a mate the male usually lets out a rolled whistle of ''ulululululululul'' and a sound similar to ''tu-wita-wit, tiwita-tu-wita, wita,'' when
perch Perch is a common name for fish of the genus ''Perca'', freshwater gamefish belonging to the family Percidae. The perch, of which three species occur in different geographical areas, lend their name to a large order of vertebrates: the Per ...
ing at a potential nest site. The female's call is usually less constant and more shrill. When alerting to danger, the northern hawk-owl lets out a sound similar to ''rike, rike, rike, rike''. It also releases a high-pitched scream followed by a ''yip'' when an intruder is near to the nest. To warn of impending dangers to a fledgling, the hawk-owl will let out a noise similar to ''ki ki kikikikiki''. Calls can vary in length from 15 s to 2 min.


Distribution and habitat

Three
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 specie ...
exist across the northern
holarctic The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical reg ...
.Voous KH, Cameron A. (1989) Owls of the northern hemisphere. Cambridge (MA): MIT Press .König C, Weick F, Wink M. 2008. Owls of the world. London: Christopher Helm. The
North American 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 ...
subspecies ''S. u. caparoch'' spans from eastern
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 ...
through Canada to
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 ...
and in some areas extends south into northern
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 Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
. The other two subspecies are found in northeastern Europe and
Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part ...
: ''S. u. tianschanica''
breed A breed is a specific group of domestic animals having homogeneous appearance (phenotype), homogeneous behavior, and/or other characteristics that distinguish it from other organisms of the same species. In literature, there exist several slig ...
s in
Central Asia Central Asia, also known as Middle Asia, is a region of Asia that stretches from the Caspian Sea in the west to western China and Mongolia in the east, and from Afghanistan and Iran in the south to Russia in the north. It includes the fo ...
reaching
Xinjiang Xinjiang, SASM/GNC: ''Xinjang''; zh, c=, p=Xīnjiāng; formerly romanized as Sinkiang (, ), officially the Xinjiang Uygur Autonomous Region (XUAR), is an autonomous region of the People's Republic of China (PRC), located in the northwes ...
(
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
); and ''S. u. ulula'' resides across Siberia reaching its most eastern range. Occasionally, ''S. u. caparoch'' can extend its territory as far south as northern
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 t ...
and many other states in the northern
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 Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
including more central states such as
West Virginia West Virginia is a state in the Appalachian, Mid-Atlantic and Southeastern regions of the United States.The Census Bureau and the Association of American Geographers classify West Virginia as part of the Southern United States while the ...
,
New York New York most commonly refers to: * New York City, the most populous city in the United States, located in the state of New York * New York (state), a state in the northeastern United States New York may also refer to: Film and television * '' ...
, and
South Dakota South Dakota (; Sioux: , ) is a U.S. state in the North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota and Dakota Sioux Native American tribes, who comprise a large po ...
. These southern forays into the northern United States are rare and generally occur during winter, or following an explosion in a population of
prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...
. ''S. u. caparoch'' can occasionally be found in more southern areas such as
Great Britain Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It ...
, southern Russia and Scandinavia, following explosions of prey. Northern hawk-owls are unevenly distributed and highly variable throughout the
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, spruc ...
. They live mostly in open
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 ext ...
forests, or coniferous forests mixed with
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, ...
species such as
larch Larches are deciduous conifers in the genus ''Larix'', of the family Pinaceae (subfamily Laricoideae). Growing from tall, they are native to much of the cooler temperate northern hemisphere, on lowlands in the north and high on mountains fur ...
,
birch A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech- oak family Fagaceae. The genus ''Betula'' cont ...
, poplar, and
willow Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist so ...
. They are found in muskegs, clearings, swamp valleys, meadows, or recently burnt areas, and generally avoid dense spruce-fir forests. Their winter habitat is usually the same as the breeding habitat.


Behaviour and ecology


Breeding

The northern hawk-owl generally starts its mating rituals at the beginning of March. After calling and pairing is complete the northern hawk-owl will build a nest and start to lay eggs. On average the northern hawk-owl will lay 3–11 eggs per
brood Brood may refer to: Nature * Brood, a collective term for offspring * Brooding, the incubation of bird eggs by their parents * Bee brood, the young of a beehive * Individual broods of North American Periodical Cicadas: ** Brood X, the largest b ...
. The nest sites are usually the tops of hollow stumps of old dead
spruce A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Earth. ''Picea'' is the sole genus in the subfam ...
trees. These nesting sites are usually above ground for the
North American 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 ...
''S. u. caparoch'' and approximately above ground for the
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 archipelag ...
n ''S. u. ulala''. The specific dates of egg appearance can be quite variable depending on locality. In central
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 to ...
eggs are usually laid from 30 March to 5 June. On
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 ...
the appearance of eggs occurs later, between 9 May and 11 June. In
Finland Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bot ...
, however, eggs can be found anywhere between 30 March to 23 June. For the most part, the female northern hawk-owl does the incubating of the eggs, whilst the male forages for food. Once the chicks have hatched their roles shift drastically. At about two weeks into the chicks' lives, the female starts to leave the nest for long spans of time (5 hours or more). This span of time is presumably when the female hunts. The male, however, will guard the nest diligently until the chicks leave. When predators (usually other raptors) fly nearby, the male will sometimes chase them away from the nest if he feels it is necessary. Once the
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 ...
ets have grown to a size which allows less parental supervision, they will leave the nest. This occurs on average after their 21st day, and can begin as early as mid-June. After this the female will provide most of the care. However, the male will remain close and will still feed his young on occasion. The northern hawk-owl has also been known to nest on cliffsides. It has little fear of humans, and will attack if the young are approached too closely.


Food and feeding

The northern hawk-owl feeds on a variety of prey, which can include small
rodents 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 nat ...
to
mammals 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 ...
more robust in size, and a variety of
birds 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 ...
— a typical diet for many boreal owls. In Eurasia the northern hawk-owl is known to feed primarily on
voles 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 low-c ...
from the
Microtus ''Microtus'' is a genus of voles found in North America, Europe and northern Asia. The genus name refers to the small ears of these animals. About 62 species are placed in the genus. They are stout rodents with short ears, legs and tails. They ea ...
family. These voles usually follow a 3–4 year cycle of abundance. Therefore, ''S. u. ulula'' numbers are affected negatively when the numbers of voles are lowest. In North America the
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 specie ...
''S. u. caparoch'' also feeds upon microtine voles, but its population is primarily based on the ten-year cycling of 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''). 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 archipelag ...
the northern hawk-owl's
biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
consists of about 94% microtine
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 low-c ...
s, whereas 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 ...
the percentage of
biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
contributed by
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 low-c ...
s can be as low as 20%. Juvenile
hares 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 ...
are considerably more important at 40–50%. Other animals that are important prey items for the northern hawk-owl include the
red squirrel The red squirrel (''Sciurus vulgaris'') is a species of tree squirrel in the genus ''Sciurus'' common throughout Europe and Asia. The red squirrel is an arboreal, primarily herbivorous rodent. In Great Britain, Ireland, and in Italy numbers ...
(''Sciurus vulgaris'') which has been documented to contribute as much as 20% to the hawk-owl's
biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
. A long list of others includes
mice A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...
, rats,
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 low-c ...
s,
lemming A lemming is a small rodent, usually found in or near the Arctic in tundra biomes. Lemmings form the subfamily Arvicolinae (also known as Microtinae) together with voles and muskrats, which form part of the superfamily Muroidea, which also include ...
s, the short-tail weasel (''Mustela erminea''),
partridge A partridge is a medium-sized Galliformes, galliform bird in any of several genera, with a wide Indigenous (ecology), native distribution throughout parts of Europe, Asia and Africa. Several species have been introduced to the Americas. They a ...
,
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''),
dove Columbidae () is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with short necks and short slender bills that in some species feature fleshy ceres. They primarily ...
s, pileated woodpeckers (''Dryocopus pileatus''), sparrows,
jay A jay is a member of a number of species of medium-sized, usually colorful and noisy, passerine birds in the Crow family, Corvidae. The evolutionary relationships between the jays and the magpies are rather complex. For example, the Eurasian m ...
s, robins,
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, ...
s,
buntings The buntings are a group of Old World passerine birds forming the genus ''Emberiza'', the only genus in the family Emberizidae. The family contains 45 species. They are seed-eating birds with stubby, conical bills. Taxonomy The family Emberizi ...
, grackles, and
finch The true finches are small to medium-sized passerine birds in the family Fringillidae. Finches have stout conical bills adapted for eating seeds and nuts and often have colourful plumage. They occupy a great range of habitats where they are usua ...
es. In the winter, feeding strategies change: where in summer the main source of food is mammals, in the winter a bigger portion of the hawk-owl's biomass consists of ground-dwelling birds, such as the
ptarmigan ''Lagopus'' is a small genus of birds in the grouse subfamily commonly known as ptarmigans (). The genus contains three living species with numerous described subspecies, all living in tundra or cold upland areas. Taxonomy and etymology The ge ...
and the
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 ...
. The northern hawk-owl is a partially diurnal hunter, although it has been recorded hunting at varying times and does not appear to have a preferred hunting time. Whether the bird resides in Eurasia or North America, the strategy is usually similar. The northern hawk-owl will perch and scour the immediate area for
prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...
. As these
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 ...
s are considered a search-oriented
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
, they likely do not stay put for long if the site is not producing prey. The hawk-owl prefers open, forest-type environments when perching. These environments include
sphagnum ''Sphagnum'' is a genus of approximately 380 accepted species of mosses, commonly known as sphagnum moss, peat moss, also bog moss and quacker moss (although that term is also sometimes used for peat). Accumulations of ''Sphagnum'' can store wa ...
bogs A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main Wetland#Types, types of wetlands. Other names for bogs include mire, mosses, quagmire, ...
and partially
deforested Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated d ...
areas. The preferred perching tree of the northern hawk-owl is the
spruce A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Earth. ''Picea'' is the sole genus in the subfam ...
tree. When the hawk-owl attacks, it goes from a horizontal posture into a gliding dive. If the prey is further away, the bird will flap its wings a few times during the dive to increase distance. The hawk-owl has exceptional hearing and can plunge into
snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout ...
to capture
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 below the surface. The type of
prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...
the hawk-owl catches will determine its eating strategy. For
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 ...
ian prey the ritual is generally the same: the northern hawk-owl will eviscerate its prey, eat the head first (especially for prey like the
red squirrel The red squirrel (''Sciurus vulgaris'') is a species of tree squirrel in the genus ''Sciurus'' common throughout Europe and Asia. The red squirrel is an arboreal, primarily herbivorous rodent. In Great Britain, Ireland, and in Italy numbers ...
, whose head is fairly large), and then — when tackling larger prey — it will eat the organs and
cache Cache, caching, or caché may refer to: Places United States * Cache, Idaho, an unincorporated community * Cache, Illinois, an unincorporated community * Cache, Oklahoma, a city in Comanche County * Cache, Utah, Cache County, Utah * Cache County ...
the remains; with smaller prey, the owl will simply swallow the body whole.


Conservation and status

Due to its low density occurrence, sporadic fluctuations, and remote breeding locations, the northern hawk-owl is one of the least studied and poorly understood birds in North America. As a result, it is almost impossible to properly estimate its numbers.Johnsgard PA. (2002) North American Owls: Biology and natural history. Washington, D.C.: Smithsonian Institution Press . 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 ...
, northern hawk-owl densities were estimated to be between zero and six pairs per . Despite these low densities, the North American population is thought to be fairly large given that they occur throughout the boreal forest. Duncan and Harris (1997) estimated that this population contains between 10,000 and 50,000 pairs. Populations are known to fluctuate with cycles of small rodents and irruptions are known to occur in sub-boreal regions throughout the world. In
Scandinavia Scandinavia; Sámi languages: /. ( ) is a subregion#Europe, subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, ...
, populations have been reported to vary from a few hundred birds in certain years to over 4000 birds in others and even up to 10,000 breeding pairs in optimal years. Irruptions can be used as indicators of small mammal abundance and in eastern North America, southern irruptions have been linked with low densities of red-backed voles in the high boreal forest. In North America, over 50% of the northern hawk-owls' breeding territory occurs in non-commercial
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, spruc ...
s and as long as nothing threatens their northern habitats, no known factors challenge their existence. However, it is unknown what effects modern forestry would have on population levels because although it would decrease nesting localities, it would simultaneously create ideal habitat for
Microtus ''Microtus'' is a genus of voles found in North America, Europe and northern Asia. The genus name refers to the small ears of these animals. About 62 species are placed in the genus. They are stout rodents with short ears, legs and tails. They ea ...
prey. Fire suppression by humans is believed to negatively affect northern hawk-owl populations by reducing open areas for hunting and dead wood to nest in. The status and conservation of this species is uncertain. A report by the Committee On the Status of Endangered Wildlife In Canada (COSEWIC) recommended that no designation be assigned for the northern hawk-owl.Duncan PA, Committee on the Status of Endangered Wildlife in Canada (1992). Status report on the northern hawk-owl, Surnia ulula. Ottawa: Committee on the Status of Endangered Wildlife in Canada. Compared to the nineteenth century, southern irruptions in the New and Old World appear to have declined. Also, North American populations seem to be declining, although no proper documentation exists to confirm this trend. In Canada, it was ranked 85th overall to set conservation, research, or monitoring priorities.Dunn EH. (1997
Setting priorities for conservation, research and monitoring of Canada's landbirds
Tech. Rep. Ser. No. 293. Can. Wildl. Serv. Ottawa, ON. Cited in: Duncan JR, Duncan PA, Poole A, editor. 1998. Northern Hawk-Owl Surnia ulula, The Birds of North America Online nternet Ithaca: Cornell Lab of Ornithology.
Downes et al. (2000) considered the hawk-owl to be of medium concern, but with a high priority to improve monitoring.Downes CM, Dunn EH, Francis CM. (2000
Canadian landbird monitoring strategy: Monitoring needs and priorities into the new millennium
Partners In Flight-Canada, Ottawa.


In falconry

The northern hawk-owl is considered a falconry bird in Ontario, and may be used to hunt small game with a proper license.


References


External links

*

– Cornell Lab of Ornithology
Northern Hawk-Owl
– eNature.com

* *
Northern Hawk-Owl information at owlpages.comNorthern Hawk-Owl profile at the Government of Canada Species at Risk Public Registry

Northern hawk-owl. Video of male, female and chicks.
* {{Taxonbar, from=Q193192
northern hawk-owl The northern hawk-owl or northern hawk owl (''Surnia ulula'') is a medium-sized true owl of the northern latitudes. It is non-migratory and usually stays within its breeding range, though it sometimes irrupts southward. It is one of the few owl ...
Holarctic birds
northern hawk-owl The northern hawk-owl or northern hawk owl (''Surnia ulula'') is a medium-sized true owl of the northern latitudes. It is non-migratory and usually stays within its breeding range, though it sometimes irrupts southward. It is one of the few owl ...
northern hawk-owl The northern hawk-owl or northern hawk owl (''Surnia ulula'') is a medium-sized true owl of the northern latitudes. It is non-migratory and usually stays within its breeding range, though it sometimes irrupts southward. It is one of the few owl ...