Snowy owl
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The snowy owl (''Bubo scandiacus''), also known as the polar owl, the white owl and the Arctic owl, is a large, white
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 ...
of the
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 ...
family. Snowy owls are native to 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 ...
regions of both North America and the
Palearctic The Palearctic or Palaearctic is the largest of the eight biogeographic realms of the Earth. It stretches across all of Eurasia north of the foothills of the Himalayas, and North Africa. The realm consists of several bioregions: the Euro-Sibe ...
, breeding mostly on the
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 ...
. It has a number of unique adaptations to its habitat and lifestyle, which are quite distinct from other extant owls. One of the largest species of owl, it is the only owl with mainly white plumage. Males tend to be a purer white overall while females tend to more have more extensive flecks of dark brown.Holt, D. W., M. D. Larson, N. Smith, D. L. Evans, and D. F. Parmelee (2020)
Snowy Owl (''Bubo scandiacus'')
version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.
Juvenile male snowy owls have dark markings that may appear similar to females until maturity, at which point they typically turn whiter. The composition of brown markings about the wing, although not foolproof, is the most reliable technique to age and sex individual snowy owls. Most owls sleep during the day and hunt at night, but the snowy owl is often active during the day, especially in the summertime. The snowy owl is both a specialized and generalist hunter. Its breeding efforts and global population are closely tied to the availability of tundra-dwelling
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 includ ...
s, but in the non-breeding season, and occasionally during breeding, the snowy owl can adapt to almost any available prey – most often other small
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 and northerly
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, as well as, opportunistically,
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 ...
. Snowy owls typically nest on a small rise on the ground of the tundra.Hume, R. (1991). ''Owls of the world''. Running Press, Philadelphia. The snowy owl lays a very large clutch of
egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
s, often from about 5 to 11, with the laying and hatching of eggs considerably staggered. Despite the short
Arctic summer The midnight sun is a natural phenomenon that occurs in the summer months in places north of the Arctic Circle or south of the Antarctic Circle, when the Sun remains visible at the local midnight. When the midnight sun is seen in the Arctic, t ...
, the development of the young takes a relatively long time and independence is sought in autumn. The snowy owl is a nomadic bird, rarely breeding at the same locations or with the same mates on an annual basis and often not breeding at all if prey is unavailable. A largely
migratory bird Bird migration is the regular seasonal movement, often north and south along a flyway, between Breeding in the wild, breeding and wintering grounds. Many species of bird migrate. Animal migration, Migration carries high costs in predation a ...
, snowy owls can wander almost anywhere close to the Arctic, sometimes unpredictably irrupting to the south in large numbers. Given the difficulty of surveying such an unpredictable bird, there was little in-depth knowledge historically about the snowy owl's status. However, recent data suggests the species is declining precipitously.Bent, A. C. (1938). ''Life Histories of North American Birds of Prey (part 2), Orders Falconiformes and Stringiformes (Vol. 170)''. US Government Printing Office. Whereas the global population was once estimated at over 200,000 individuals, recent data suggests that there are probably fewer than 100,000 individuals globally and that the number of successful breeding pairs is 28,000 or even considerably less. While the causes are not well understood, numerous, complex environmental factors often correlated with
global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
are probably at the forefront of the fragility of the snowy owl's existence.


Taxonomy

The snowy owl was one of the many bird species originally described by
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 ...
in his landmark 1758 10th edition of ''Systema Naturae'', where it was given the binomial name ''Strix scandiaca''. The genus name ''Bubo'' is
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
for "an
horned owl The American (North and South America) horned owls and the Old World eagle-owls make up the genus ''Bubo'', at least as traditionally described. The genus name ''Bubo'' is Latin for the Eurasian eagle-owl. This genus contains 19 species that ar ...
" and ''scandiacus'' is
New Latin New Latin (also called Neo-Latin or Modern Latin) is the revival of Literary Latin used in original, scholarly, and scientific works since about 1500. Modern scholarly and technical nomenclature, such as in zoological and botanical taxonomy ...
for "of
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, ...
". The former generic name ''Nyctea'' is derived from Greek meaning "night". Linnaeus originally described the different plumages of this owl as separate species, with the male specimens of snowy owls being considered ''Strix scandiaca'' and the likely females considered as ''Strix nyctea''. Until recently, the snowy owl was regarded as the sole member of a distinct
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 ...
, as ''Nyctea scandiaca'', but
mtDNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial DNA ...
cytochrome ''b''
sequence In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is calle ...
data shows that it is very closely related to the
horned owl The American (North and South America) horned owls and the Old World eagle-owls make up the genus ''Bubo'', at least as traditionally described. The genus name ''Bubo'' is Latin for the Eurasian eagle-owl. This genus contains 19 species that ar ...
s in the genus ''Bubo'' and the species is now thusly often considered inclusive with that genus.Wink, M. & Heidrich, P. (2000). "Molecular systematics of owls (Strigiformes) based on DNA-sequences of the mitochondrial cytochrome b gene", pp. 819–828 in: Chancellor, R.D. & Meyburg, B.U. eds. (2000). ''Raptors at Risk. Proceedings of the V World Conference on Birds of Prey and Owls''. Midrand, Johannesburg, 4–11 August 1998. WWGBP & Hancock House, Berlin & Blaine, Washington. However, some authorities debate this classification, still preferring ''Nyctea''. Often authorities are motivated to retain the separate genus on the grounds of osteological distinctions.Ford, N. L. (1967). ''A systematic study of the owls based on comparative osteology''. PhD diss, Univ. of Michigan, Ann Arbor. Genetic testing revealed a reasonably distinct genetic makeup for snowy owls, being about 8% genetically distinct from other ''Bubo'' owls, perhaps giving credence to those who count the species as separate under ''Nyctea''. However, a fairly recent shared origin in evolutionary history has been illustrated through a combination of genetic study and fossil review and there is little, other than osteology of the tarsometatarsus, to outright distinguish the snowy owl from other modern species like the
Eurasian eagle-owl The Eurasian eagle-owl (''Bubo bubo'') is a species of eagle-owl that resides in much of Palearctic, 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, ...
(''Bubo bubo''). Genetic testing has indicated that the snowy owl may have diverged from related species at around 4 million years ago. Furthermore, it has determined that the living species genetically most closely related to the snowy owl is the
great horned owl 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 native to the Americas. It is an extrem ...
(''Bubo virginianus''). On a broader scale, owls in general have, through genetic materials, been determined to be a highly distinct group, with outwardly similar groups such as
Caprimulgiformes Nightjars are medium-sized nocturnal or crepuscular birds in the family Caprimulgidae and order Caprimulgiformes, characterised by long wings, short legs, and very short bills. They are sometimes called goatsuckers, due to the ancient folk tal ...
revealed to not be at all closely related. Within the owl order,
typical owls 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 ...
are highly divergent from
barn-owl Barn-owls (family Tytonidae) are one of the two families of owls, the other being the true owls or typical owls, Strigidae. They are medium to large owls with large heads and characteristic heart-shaped faces. They have long, strong legs with p ...
s. Furthermore, the ''Bubo'' genus likely clustered at some point during the evolutionary process with other largish owls, such as ''
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 ...
'', ''
Pulsatrix ''Pulsatrix'' is a genus of owl in the family Strigidae. They are called spectacled owls because of their prominent facial pattern. The genus contains the following species: * Spectacled owl, '' Pulsatrix perspicillata'' * Tawny-browed owl, '' ...
'' and '' Ciccaba'', based on broad similarities in their voice, reproductive behaviors (i.e. hooting postures) and a similar number and structure of
chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...
s and
autosome An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosome, allosomal (sex chromosome) pairs, which may have different structures. The DNA in au ...
s. A number, but not all, of extant typical owls seem to have evolved from an ancient shared
common ancestor Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. All living beings are in fact descendants of a unique ancestor commonly referred to as the last universal comm ...
with the ''Bubo'' owls. In addition to the question of relationship of the traditional ''Bubo'' owls to the snowy owls, ongoing ambiguity of the relationship of other similarly large-sized owls has been persistent. These have sometimes either been included in the genus or within separate genera, i.e. the '' Ketupu'' or fish owls and the ''
Scotopelia Fishing owls are a group of sub-Saharan African birds in the family Strigidae, the true owls. Fishing owls have traditionally been placed in the genus ''Scotopelia'', but DNA evidence suggests they should be included in genus ''Bubo A bubo ( ...
'' or fishing owls. Despite the adaptive distinctions, the grouping of these large owls (i.e. ''Bubo'', snowy, fish and perhaps fishing owls) appears to be borne out via research of
karyotype A karyotype is the general appearance of the complete set of metaphase chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is disce ...
s.''Owls of the World: A Photographic Guide'' by Mikkola, H. Firefly Books (2012), The
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
history of snowy owls is fairly well documented despite some early confusion on how to distinguish the skeletal structure of the snowy owls from eagle-owls. It was determined that the snowy owl once was distributed much more widely and far farther to the south during the
Quaternary glaciation The Quaternary glaciation, also known as the Pleistocene glaciation, is an alternating series of glacial and interglacial periods during the Quaternary period that began 2.58 Ma (million years ago) and is ongoing. Although geologists describe ...
when much of the
Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...
was in the midst of an
ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...
. Fossil records shows that snowy owls once could be found in Austria, Azerbaijan,
Czechoslovakia , rue, Чеськословеньско, , yi, טשעכאסלאוואקיי, , common_name = Czechoslovakia , life_span = 1918–19391945–1992 , p1 = Austria-Hungary , image_p1 ...
, England, France, Germany, Hungary, Italy, Poland, Sardinia and Spain as well as in the Americas in
Cape Prince of Wales Cape Prince of Wales (Russian: Мыс Принца Уэльского) () is the westernmost mainland point of the Americas. It was named in 1778 by Captain James Cook of the British Royal Navy, presumably for the Prince of Wales at the time, Geo ...
,
Little Kiska Island Little Kiska Island is an island off east coast of the island of Kiska in the Rat Islands (part of the Aleutian Islands)in Alaska. It lies immediately east of Kiska Harbor it is approximately 6 kilometers long and 2 kilometers wide. The island ha ...
,
St. Lawrence Island St. Lawrence Island ( ess, Sivuqaq, russian: Остров Святого Лаврентия, Ostrov Svyatogo Lavrentiya) is located west of mainland Alaska in the Bering Sea, just south of the Bering Strait. The village of Gambell, located on t ...
, and in
Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. Its largest metropolitan areas include the Chicago metropolitan area, and the Metro East section, of Greater St. Louis. Other smaller metropolita ...
. In the
Late Pleistocene The Late Pleistocene is an unofficial Age (geology), age in the international geologic timescale in chronostratigraphy, also known as Upper Pleistocene from a Stratigraphy, stratigraphic perspective. It is intended to be the fourth division of ...
the range expanded southward even more so to Bulgaria (80,000–16,000 years,
Kozarnika Kozarnika or Peshtera Kozarnika ( bg, Пещера Козарника, , The Goat Shed) is a cave in northwestern Bulgaria that was used as a hunters’ shelter as early as the Lower Paleolithic (1.6-1.4 million BP). It marks an older rou ...
Cave, W Bulgaria). and much of the Italian Peninsula.
Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), 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 fina ...
era fossils from France, i.e. ''B. s. gallica'', showed that the snowy owls of the time were somewhat bulkier (though still notably smaller than contemporary eagle-owls of the times, which were larger than the eagle-owls of today) and osteologically more sexually dimorphic in size than the modern form (9.9% dimorphism in favor of females in the fossils against 4.8% in the same features today). There are no subspecific or other geographical variations reported in the modern snowy owls, with individuals of vastly different origins breeding together readily due to their nomadic habits. Despite apparent variations in body size, environmental conditions are the likely variant rather than genetics. No evidence could be found of phylogeographic variation in snowy owls upon testing. Furthermore, the snowy owl appears to have a similar level of genetic diversity as other European owls.


Hybrids

Snowy owls are not known to interbreed with other owl species in the wild, and accordingly, no hybrids of snowy owls and other owl species have yet been sighted in the wild. However, a hobby falconer in
Kollnburg Kollnburg is a municipality in the district of Regen, in Bavaria, Germany. A part of the municipal area, including the parish village of the same name, is a state-approved resort. Geography The community is located in the Donau Forest region in th ...
, Germany, bred hybrids from a male snowy owl and a female Eurasian eagle-owl (''Bubo bubo'') in 2013."Schnuhu": Überraschende Kreuzung – Ich bin Bayerns süßester Fratz!
tz.de Retrieved on 7 October 2016
The two resulting male hybrid owls possessed the prominent ear-tufts (generally absent in snowy owls), general size, orange eyes, and the same pattern of black markings on their plumage from their Eurasian eagle-owl mother, while retaining the generally black-and-white plumage colours from their snowy owl father. The hybrids were dubbed "''Schnuhus''" from the German words for snowy owl and Eurasian eagle-owl (''Schnee-Eule'' and ''Uhu'', respectively). As of 2014, the hybrids had grown to maturity and were healthy.


Description

The snowy owl is mostly white. They are purer white than predatory mammals like
polar bear The polar bear (''Ursus maritimus'') is a hypercarnivorous bear whose native range lies largely within the Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the largest extant bear specie ...
s (''Ursus maritimus'') and
Arctic fox The Arctic fox (''Vulpes lagopus''), also known as the white fox, polar fox, or snow fox, is a small fox native to the Arctic regions of the Northern Hemisphere and common throughout the Arctic tundra biome. It is well adapted to living in ...
(''Vulpes lagopus''). Often when seen in the field, these owls can resemble a pale rock or a lump of snow on the ground. It usually appears to lack ear tufts but very short (and probably vestigial)
tufts Tufts University is a private research university on the border of Medford and Somerville, Massachusetts. It was founded in 1852 as Tufts College by Christian universalists who sought to provide a nonsectarian institution of higher learning ...
can be erected in some situations, perhaps most frequently by the female when she is sitting on the nest. The ear tufts measure about and consist of about 10 small feathers. The snowy owl has bright yellow eyes. The head is relatively small and, even for the relatively simply adapted hearing mechanism of a ''Bubo'' owl, the
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 ...
is shallow and the ear is uncomplicated. 1 male had ear slits of merely on left and on the right. Females are almost invariably more duskily patterned than like-age males. In mature males, the upper parts are plain white with usually a few dark spots on the miniature ear-tufts, about the head and the tips of some primaries and secondaries whilst the underside is often pure white. Despite their reputation for being purely white, only 3 out of 129 Russian museum specimens of adult males showed an almost complete absence of darker spots. The adult female is usually considerably more spotted and often slightly barred with dark brown on the crown and the underparts. Her flight and tail feathers are faintly barred brown while the underparts are white in base color with brown spotting and barring on the flanks and upper breast. In confusingly plumaged snowy owls, the sex can be determined by the shape of wing markings, which manifest as bars more so in females and spots in males. However, the very darkest males and the lightest females are nearly indistinguishable by plumage. On rare occasion, a female can appear almost pure white, as has been recorded in both the field and in captivity.McMorris, A. (2011). ''Snowy Owls: Age, Sex and Plumage''. Presentation Delaware Valley Ornithological Club. There is some evidence that some of the species grow paler with age after maturity.Dementiev, G. P., Gladkov, N. A., Ptushenko, E. S., Spangenberg, E. P., & Sudilovskaya, A. M. (1966). ''Birds of the Soviet Union, vol. 1''. Israel Program for Scientific Translations, Jerusalem. One study's conclusions were that males were usually but not always lighter and that correctly aging is extremely difficult, sometimes individuals either get lighter, darker or do not change their appearance with age. On the other hand, with close study, it is possible to visually identify even individual snowy owls using the pattern of markings on the wing, which can be somewhat unique in each individual. After a fresh moult, some adult females that previously appeared relatively pale newly evidenced dark, heavy markings. On the contrary, some banded individuals over at least four years were observed to have been almost entirely unchanged in the extent of their markings. In another very pale owl, the barn owl (''Tyto alba''), the sexual dimorphism of spotting appears to be driven by genetics while, in snowy owls, environment may be the dictating factor instead. The chicks are initially grayish white but quickly transition to dark gray-brown in the mesoptile plumage. This type of plumage
camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the ...
s effectively against the variously colored
lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.moult In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
fewer or more broken bars are usually evidenced on the wing. The extent of white and composition of wing patterns become more dimorphic by sex with each juvenile moult, culminating in the 4th or 5th pre-basic moult, wherein the owls are hard to distinguish from mature adults. Moults usually occur from July and September, non-breeding birds moulting later and more extensively, and are never extensive enough to render the owls flightless. Evidence indicates that snowy owls may attain adult plumage at 3 to 4 years of age, but fragmentary information suggests that some males are not fully mature and/or as fully white in plumage that they can attain until the 9th or 10th year. Generally speaking, moults of snowy owls occur more quickly than do those of Eurasian eagle-owls. The toes of the snowy owl are extremely thickly feathered white, while the claws are black. The toe feathers are the longest known of any owl, averaging at , against the great horned owl which has the 2nd longest toe feathers at a mean of Occasionally, snowy owls may show a faint blackish edge to the eyes and have a dark gray cere, though this is often not visible from the feather coverage, and a black bill. Unlike many other whitish birds, the snowy owl does not possess black wingtips, which is theorized to minimize wear-and-tear on the wing feathers in the other whitish bird types. The conspicuously notched primaries of the snowy owl appear to give an advantage over similar owls in long-distance flight and more extensive flapping flight. The snowy owl does have some of the noise-canceling serrations and comb-like wing feathers that render the flight of most owls functionally silent, but they have fewer than most related ''Bubo'' owls. Therefore, in combination with its less soft feathers, the flight of a snowy owl can be somewhat audible at close range. The flight of snowy owls tends to be steady and direct and is reminiscent to some of the flight of a large, slow-flying falcon. Though capable of occasional
gliding flight Gliding flight is heavier-than-air flight without the use of thrust; the term volplaning also refers to this mode of flight in animals. It is employed by gliding animals and by aircraft such as gliders. This mode of flight involves flying a s ...
, there is no evidence that snowy owls will soar. It is said that the species seldom exceeds a flying height of around even during passage. While the feet are sometimes described as "enormous", the tarsus is in osteological terms relatively short at 68% the length of those of a Eurasian eagle-owl but the claws are nearly as large, at 89% of the size of those of the eagle-owl. Despite its relatively short length, the tarsus is of similar circumference as in other ''Bubo'' owls. Also compared to an eagle-owl, the snowy owl has a relatively short decurved
rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...
, a proportionately greater length to the interorbital roof and a much longer
sclerotic ring Sclerotic rings are rings of bone found in the eyes of many animals in several groups of vertebrates, except for mammals and crocodilians. They can be made up of single bones or multiple segments and take their name from the sclera. They are bel ...
surrounding the eyes while the anterior opening are the greatest known in any owl. Owls have extremely large eyes which are nearly the same size in large species such as the snowy owl as those of humans. The snowy owl's eye, at about in diameter, is slightly smaller than those of great horned and Eurasian eagle-owls but is slightly larger than those of some other large owls. Snowy owls must be able to see from great distances and in highly variable conditions but probably possess less acute night vision than many other owls. Based on the study of dioptres in different owl species, the snowy owl was determined to have eyesight better suited to long-range perception than to close discrimination, while some related species such as great horned owls could probably more successful perceive closer objects. Despite their visual limits, snowy owls may have up to 1.5 times more visual acuity than humans. Like other owls, snowy owls can probably perceive all colors but cannot perceive
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
visual pigments. Owls have the largest brains of any bird (increasing in sync with the size of the owl species), with the size of the brain and eye related less to
intelligence Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, critical thinking, and problem-solving. More generally, it can b ...
than perhaps to increased nocturnality and predatory behavior.


Size

The snowy owl is a very large owl. They are the largest avian predator of the
High Arctic High may refer to: Science and technology * Height * High (atmospheric), a high-pressure area * High (computability), a quality of a Turing degree, in computability theory * High (tectonics), in geology an area where relative tectonic uplift to ...
and one of the largest owls in the world. Snowy owls are about the sixth or seventh heaviest living owl on average, around the fifth longest and perhaps the third longest winged.Weidensaul, S. (2015). ''Owls of North America and the Caribbean''. Houghton Mifflin Harcourt. This species is the heaviest and longest winged owl (as well as the second longest) in North America, the second heaviest and longest winged owl in Europe (and third longest) but is outsized in bulk by about 3 to 4 other species in Asia. Despite being sometimes described as of similar size, the snowy owl is somewhat larger in all aspects of average size than the
great horned owl 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 native to the Americas. It is an extrem ...
while the similarly specialized
taiga 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, spruce ...
-dwelling
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 ...
(''Strix nebulosa''), is longer in total length and of similar dimensions in standard measurements, but is shorter winged and much less heavy than the snowy owl. In Eurasia, the
Eurasian eagle-owl The Eurasian eagle-owl (''Bubo bubo'') is a species of eagle-owl that resides in much of Palearctic, 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, ...
is larger in all standards of measurements than the snowy owl not to mention two additional species each from Africa and Asia that are slightly to considerably heavier on average than the snowy owl. Like most
birds of prey Birds of prey or predatory birds, also known as raptors, are hypercarnivorous bird species that actively hunt and feed on other vertebrates (mainly mammals, reptiles and other smaller birds). In addition to speed and strength, these predators ...
, the snowy owl shows reverse sexual dimorphism relative to most non-raptorial birds in that females are larger than males. Sexual dimorphism that favors the female may have some correlation with being able to more effectively withstand food shortages such as during brooding as well as the rigors associated with incubating and brooding. Females are sometimes described as “giant” whereas males appear relatively “neat and compact”. However, the sexual dimorphism is relatively less pronounced compared to some other ''Bubo'' species. Male snowy owls have been known to measure from in total length, with an average from four large samples of and a maximum length, perhaps in need of verification, of reportedly .Eckert, A. W. (1987). ''The Owls of North America, North of Mexico: All the Species and Subspecies Illustrated in Color and Fully Described''. Gramercy.Parmelee, D. F. (1972). ''Canada's incredible arctic owls''. Beaver no. summer:30–41.Priklonskiy, S.G. (1993). ''Snowy Owl — Nyctea scandiaca (Linnaeus, 1758)''. In: ''Birds of Russia and adjoining regions: Pterocliformes, Columbiformes, Cuculiformes, Strigiformes''. Moscow, p. 258–270. (in Russian). In wingspan, males may range from , with a mean of . In females, total length has been known to range from , with a mean of and an unverified maximum length of perhaps (if so they would have the second longest maximum length of any living owl, after only the great grey owl). Female wingspans have reportedly measured from , with a mean of . Despite one study claiming that snowy owl had the highest
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 ...
(i.e. grams per square cm of wing area) of any of 15 well-known owl species, more extensive sampling demonstratively illustrated that the wing loading of snowy owls is notably lower than Eurasian eagle- and great horned owls. The conspicuously long-winged profile of a flying snowy owl compared to these related species may cause some to compare their flight profile to a bulkier version of an enormous ''
Buteo ''Buteo'' is a genus of medium to fairly large, wide-ranging raptors with a robust body and broad wings. In the Old World, members of this genus are called "buzzards", but " hawk" is used in the New World (Etymology: ''Buteo'' is the Latin na ...
'' or a large
falcon Falcons () are birds of prey in the genus ''Falco'', which includes about 40 species. Falcons are widely distributed on all continents of the world except Antarctica, though closely related raptors did occur there in the Eocene. Adult falcons ...
. Body mass in males can average from , with a median of and a full weight range of from six sources. Body mass in females can average from , with a median of and a full weight range of . Larger than the aforementioned body mass studies, a massive pooled dataset at six wintering sites in North America showed that 995 males averaged at while 1,189 females were found to average . Reported weights of down to for males and of for females are probably in reference to owls in a state of
starvation Starvation is a severe deficiency in caloric energy intake, below the level needed to maintain an organism's life. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, dea ...
. Such emaciated individuals are known to highly impaired and starvation deaths are probably not infrequent in winters with poor food accesses. Standard measurements have been even more widely reported than length and wingspan. The wing chord of males can vary from , averaging from with a median of . The wing chord of females can vary from , averaging from with a median of . 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 ...
length of males can vary on average from , with a full range of and a median of . The tail length of females can average from , with a full range of and a median of . Data indicates that slightly longer wing chord and tail lengths were reported on average in Russian data than in American research, however the weights were not significantly different in the two regions. Less widely taken measurements include the culmen, which can measure from with a median average of in males and in females, and the total bill length which is from , with an average in both sexes of . Tarsal length in males averages about , with a range of , and averages about , with a range of , in females.


Identification

The snowy owl is certainly one of the most unmistakable owls (or perhaps even animals) in the world. No other species attains the signature white stippled sparsely with black-brown color of these birds, a coloring which renders their bright yellow eyes all the more detectable, nor possesses their obvious extremely long feathering. The only other owl to breed in the
High Arctic High may refer to: Science and technology * Height * High (atmospheric), a high-pressure area * High (computability), a quality of a Turing degree, in computability theory * High (tectonics), in geology an area where relative tectonic uplift to ...
is the
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 ...
(''Asio flammeus''). Both species inhabit open country, overlap in range and are often seen by day, but the short-eared is much smaller and more tan or straw-colored in coloration, with streaked brown on chest. Even the palest short-eared owls conspicuously differ and are darker than the snowy owl; additionally the short-eared most often hunts in extended flights.Pyle, P. (1997). ''Identification Guide to North American Birds, Part I: Columbidae to Ploceidae''. Slate Creek Press, Bolinas, CA, USA. More similar owls such as the
Eurasian eagle-owl The Eurasian eagle-owl (''Bubo bubo'') is a species of eagle-owl that resides in much of Palearctic, 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 the
great horned owl 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 native to the Americas. It is an extrem ...
attain a fairly pale, sometimes white-washed look in their northernmost races. These species do not normally breed nearly as far north as snowy owls but overlaps certainly do occur when snowy owls when the latter owl sometimes comes south in winter. However, even the most pale great horned and Eurasian eagle-owls are still considerably more heavily marked with darker base colors than snowy owls (the whitest eagle-owls are paler than the whitest great horned owls), possess much larger and more conspicuous
ear tuft Ear tufts are a collection of fur or feathers found on animals which can resemble an animal's ear or is near the animal's ear. Cats Ear tufts are not found on all cat breeds. The ear tufts are located on the tips of cat ears and are also known ...
s and lack the bicolored appearance of the darkest snowy owls. While the great horned owl has yellow eyes like the snowy owl, the Eurasian eagle-owl tends to have bright orange eyes. The
open terrain Open terrain, open country or open ground is terrain which is mostly flat and free of obstructions such as trees and buildings. Examples include farmland, grassland and specially cleared areas such as an airport. Such terrain is significant in ...
habitats normally used by wintering snowy owls are also distinct from the typical
edge Edge or EDGE may refer to: Technology Computing * Edge computing, a network load-balancing system * Edge device, an entry point to a computer network * Adobe Edge, a graphical development application * Microsoft Edge, a web browser developed by ...
and
rock Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wales ...
y habitats usually favored by the great horned and Eurasian eagle-owls, respectively.


Vocalizations

The snowy owl differ in their calls from other ''Bubo'' owls, with a much more barking quality to their version of a hooting song. Perhaps as many as 15 different calls by mature snowy owls have been documented.Sutton, G. M. (1932). ''The exploration of Southampton Island. Part II, Zoölogy. Section 2.-The birds of Southampton Island''. Memoirs of the Carnegie Museum 12 (2):1–275. The main vocalization is a monotonous sequence that normally contains 2–6 (but occasionally more), rough notes similar to the rhythm of a barking dog: ''krooh krooh krooh krooh''... The call may end with an emphatic ''aaoow'', which is somewhat reminiscent of the deep alarm call of a
great black-backed gull The great black-backed gull (''Larus marinus'') is the largest member of the gull family. Described by the Cornell Lab of Ornithology as "the king of the Atlantic waterfront", it is a very aggressive hunter, pirate, and scavenger. It breeds on t ...
(''Larus marinus''). They will call mainly from a perch but also sometimes do so in flight. The ''krooh'' call of the male snowy owl may perform multiple functions such as competitive exclusion of other males and advertising to females.Taylor, P.S. (1973). ''Breeding behaviour of the Snowy Owl''. Living Bird. 12: 137–154. The calls of this species may carry exceptionally far in the thin air of Arctic, certainly over more than , and maybe even to as much away. The female has a similar call to male but can be higher-pitched and/or more guttural as well as single notes which are often disyllabic, ''khuso''. Female snowy owls have also been known to utter chirps and high screaming notes, similar to those of the nestlings. Both sexes may at times give a series of clucking, squeals, grunts, hisses and cackles, perhaps such as in circumstances when they are excited. The alarm call is a loud, grating, hoarse ''keeea''. Another raspier bark is recorded, sometimes called a "watchman's rattle" call, and may be transcribed as ''rick, rick, rick'', ''ha, how, quack, quock'' or ''kre, kre, kre, kre, kre''. A female attacking to protect her nest was recorded to let out a crowed ''ca-ca-oh'' call, whilst other owls attacking to protect the nest did a loud version of the typical call while circling before dropping down. They may also clap their beak in response to threats or annoyances. While called clapping, it is believed this sound may actually be a clicking of the tongue, not the beak. Though largely only vocal in the breeding season, leading to some erroneous older accounts describing the snowy owl as completely silent, some vocalizations have been recorded in winter in the northern United States. Initially, the young of the snowy owl have a high pitched and soft begging call which develops into a strong, wheezy scream at around 2 weeks. At the point when the young owls leave the nest around 3 weeks, the shrill squeals they emit may allow the mothers to locate them.


Distribution and habitat


Breeding range

The snowy owl is typically found in the northern circumpolar region, where it makes its summer home north of latitude 60° north though sometimes down to 55 degrees north. However, it is a particularly
nomad A nomad is a member of a community without fixed habitation who regularly moves to and from the same areas. Such groups include hunter-gatherers, pastoral nomads (owning livestock), tinkers and trader nomads. In the twentieth century, the popu ...
ic bird, and because population fluctuations in its
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 ...
species can force it to relocate, it has been known to breed at more southerly latitudes. Although the total breeding range includes a little over , only about have a high probability of breeding, i.e. breeding at no more than 3–9-year intervals. Snowy owls nest in the 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 moun ...
of the northernmost stretches of
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., ...
, Northern Canada, and the Euro-Siberian region. Between 1967 and 1975, snowy owls bred on the remote island of
Fetlar Fetlar ( sco, Fetlar) is one of the North Isles of Shetland, Scotland, with a usually resident population of 61 at the time of the 2011 census. Its main settlement is Houbie on the south coast, home to the Fetlar Interpretive Centre. Fetlar i ...
in the
Shetland Shetland, also called the Shetland Islands and formerly Zetland, is a subarctic archipelago in Scotland lying between Orkney, the Faroe Islands and Norway. It is the northernmost region of the United Kingdom. The islands lie about to the no ...
Isles north of mainland
Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...
, discovered by the Shetland
RSPB The Royal Society for the Protection of Birds (RSPB) is a Charitable_organization#United_Kingdom, charitable organisation registered in Charity Commission for England and Wales, England and Wales and in Office of the Scottish Charity Regulator, ...
warden, Bobby Tulloch. Females summered as recently as 1993, but their status in the
British Isles The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...
is now that of a rare winter visitor to Shetland, the
Outer Hebrides The Outer Hebrides () or Western Isles ( gd, Na h-Eileanan Siar or or ("islands of the strangers"); sco, Waster Isles), sometimes known as the Long Isle/Long Island ( gd, An t-Eilean Fada, links=no), is an island chain off the west coast ...
and the
Cairngorms The Cairngorms ( gd, Am Monadh Ruadh) are a mountain range in the eastern Highlands of Scotland closely associated with the mountain Cairn Gorm. The Cairngorms became part of Scotland's second national park (the Cairngorms National Park) on 1 S ...
. Older records show that the snowy owls may have once semi-regularly bred elsewhere in the
Shetland Shetland, also called the Shetland Islands and formerly Zetland, is a subarctic archipelago in Scotland lying between Orkney, the Faroe Islands and Norway. It is the northernmost region of the United Kingdom. The islands lie about to the no ...
s. They range in northern Greenland (mostly
Peary Land Peary Land is a peninsula in northern Greenland, extending into the Arctic Ocean. It reaches from Victoria Fjord in the west to Independence Fjord in the south and southeast, and to the Arctic Ocean in the north, with Cape Morris Jesup, the nort ...
) and, rarely in "isolated parts of the highlands", Iceland. Thence, they are found breeding at times across northern
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 ...
such as in
Spitsbergen Spitsbergen (; formerly known as West Spitsbergen; Norwegian: ''Vest Spitsbergen'' or ''Vestspitsbergen'' , also sometimes spelled Spitzbergen) is the largest and the only permanently populated island of the Svalbard archipelago in northern Norw ...
and western and northern
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, ...
. In Norway, they normally breed in
Troms og Finnmark Troms og Finnmark (; sme, Romsa ja Finnmárku ; fkv, Tromssa ja Finmarkku; fi, Tromssa ja Finnmark, lit. Troms and Finnmark in English language, English), is a Counties of Norway, county in Northern Norway, northern Norway that was established ...
and seldom down as far south as
Hardangervidda Hardangervidda ( en, Hardanger Plateau) is a mountain plateau (Norwegian: ''vidde'') in central southern Norway, covering parts of Vestland, Vestfold og Telemark, and Viken counties. It is the largest plateau of its kind in Europe, with a cold ye ...
and in Sweden perhaps down to the
Scandinavian Mountains The Scandinavian Mountains or the Scandes is a mountain range that runs through the Scandinavian Peninsula. The western sides of the mountains drop precipitously into the North Sea and Norwegian Sea, forming the fjords of Norway, whereas to the ...
while breeding is very inconsistent in Finland. They also range in much of northern Russia, including northern
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 of ...
,
Anadyr Anadyr may refer to: *Anadyr (town), a town and the administrative center of Chukotka Autonomous Okrug, Russia *Anadyr District *Anadyr Estuary *Anadyr (river), a river in Chukotka Autonomous Okrug, Russia *Anadyr Highlands *Anadyr Lowlands *Operati ...
, Koryakland,
Taymyr Peninsula The Taymyr Peninsula (russian: Таймырский полуостров, Taymyrsky poluostrov) is a peninsula in the Far North of Russia, in the Siberian Federal District, that forms the northernmost part of the mainland of Eurasia. Administrat ...
,
Yugorsky Peninsula The Yugorsky Peninsula (russian: Югорский полуостров) is a large peninsula in Nenets Autonomous Okrug, Russia. It is limited by the Khaypudyr Bay in the Pechora Sea to the west and by the Baydaratsk Bay in the Kara Sea to the n ...
,
Sakha Sakha, officially the Republic of Sakha (Yakutia),, is the largest republic of Russia, located in the Russian Far East, along the Arctic Ocean, with a population of roughly 1 million. Sakha comprises half of the area of its governing Far Ea ...
(especially the
Chukochya River The Bolshaya Chukochya or Chukochya (russian: Большая Чукочья; ckt, Рэвум-Рэву, ''Revum-Revu'') is a river in the Sakha Republic (Yakutia) of the Russian Federation. It is long, and has a drainage basin of . Course It ha ...
) and
Sakhalin Sakhalin ( rus, Сахали́н, r=Sakhalín, p=səxɐˈlʲin; ja, 樺太 ''Karafuto''; zh, c=, p=Kùyèdǎo, s=库页岛, t=庫頁島; Manchu: ᠰᠠᡥᠠᠯᡳᠶᠠᠨ, ''Sahaliyan''; Orok: Бугата на̄, ''Bugata nā''; Nivkh: ...
. Breeding has also been reported sporadically to the south in the
Komi Republic The Komi Republic (russian: Республика Коми; kv, Коми Республика), sometimes simply referred to as Komi, is a republic of Russia located in Eastern Europe. Its capital is the city of Syktyvkar. The population of the ...
and even the
Kama River The Kama (russian: Ка́ма, ; tt-Cyrl, Чулман, ''Çulman''; udm, Кам) is a long«Река ...
in southern
Perm Krai Perm Krai (russian: Пе́рмский край, r=Permsky kray, p=ˈpʲɛrmskʲɪj ˈkraj, ''Permsky krai'', , ''Perem lador'') is a federal subject of Russia (a krai) that came into existence on December 1, 2005 as a result of the 2004 refe ...
. Although considered part of their regular range, the last breeding by snowy owls in the
Kola Peninsula sjd, Куэлнэгк нёа̄ррк , image_name= Kola peninsula.png , image_caption= Kola Peninsula as a part of Murmansk Oblast , image_size= 300px , image_alt= , map_image= Murmansk in Russia.svg , map_caption = Location of Murmansk Oblas ...
was in the early 1980s; similarly, breeding maps show the species in
Arkhangelsk Oblast Arkhangelsk Oblast (russian: Арха́нгельская о́бласть, ''Arkhangelskaya oblast'') is a federal subjects of Russia, federal subject of Russia (an oblast). It includes the Arctic Ocean, Arctic archipelagos of Franz Josef Land ...
and the
Pay-Khoy Ridge The Pay-Khoy Range ( rus, хребет Пай-Хой) is a mountain range at the northern end of the Ural Mountains. It lies within the Nenets Autonomous Okrug. Geography The ridge is extended from northwest to southeast. It is located on the Yu ...
but no breeding records are known in at least 30 years in either. They range throughout most of the Arctic isles of Russia such as
Novaya Zemlya Novaya Zemlya (, also , ; rus, Но́вая Земля́, p=ˈnovəjə zʲɪmˈlʲa, ) is an archipelago in northern Russia. It is situated in the Arctic Ocean, in the extreme northeast of Europe, with Cape Flissingsky, on the northern island, ...
,
Severnaya Zemlya Severnaya Zemlya (russian: link=no, Сéверная Земля́ (Northern Land), ) is a archipelago in the Russian high Arctic. It lies off Siberia's Taymyr Peninsula, separated from the mainland by the Vilkitsky Strait. This archipelago s ...
,
New Siberian Islands The New Siberian Islands ( rus, Новосиби́рские Oстрова, r=Novosibirskiye Ostrova; sah, Саҥа Сибиир Aрыылара, translit=Saña Sibiir Arıılara) are an archipelago in the Extreme North of Russia, to the north o ...
,
Wrangel Island Wrangel Island ( rus, О́стров Вра́нгеля, r=Ostrov Vrangelya, p=ˈostrəf ˈvrangʲɪlʲə; ckt, Умӄиԓир, translit=Umqiḷir) is an island of the Chukotka Autonomous Okrug, Russia. It is the 91st largest island in the w ...
,
Commander Commander (commonly abbreviated as Cmdr.) is a common naval officer rank. Commander is also used as a rank or title in other formal organizations, including several police forces. In several countries this naval rank is termed frigate captain. ...
and
Hall Islands The Hall Islands are a group of two large atolls in the northern part of the state of Chuuk, Federated States of Micronesia. In the broader sense, a third and smaller atoll is included. Nomwin, the western atoll, and Murilo, the eastern one, a ...
. In North America, the breeding range has been known in modern times to include the
Aleutians The Aleutian Islands (; ; ale, Unangam Tanangin,”Land of the Aleuts", possibly from Chukchi ''aliat'', "island"), also called the Aleut Islands or Aleutic Islands and known before 1867 as the Catherine Archipelago, are a chain of 14 large vo ...
(i.e.
Buldir Buldir Island (also sometimes written Buldyr; ale, Idmaax; russian: Булдырь) is a small island in the western Aleutian Islands of the U.S. state of Alaska. It is long and wide with an area of . Buldir is farther from the nearest lan ...
and Attu) and much of northern
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., ...
, most frequently from the
Arctic National Wildlife Refuge The Arctic National Wildlife Refuge (ANWR or Arctic Refuge) is a national wildlife refuge in northeastern Alaska, United States on traditional Gwich'in lands. It consists of in the Alaska North Slope region. It is the largest national wildli ...
to
Utqiaġvik Utqiagvik ( ik, Utqiaġvik; , , formerly known as Barrow ()) is the borough seat and largest city of the North Slope Borough in the U.S. state of Alaska. Located north of the Arctic Circle, it is one of the northernmost cities and towns in the ...
, and more sporadically down along the coastal-western parts such as through Nome,
Hooper Bay Hooper Bay ( esu, Naparyaarmiut) is a city in Kusilvak Census Area, Alaska, United States. At the 2020 census the population was 1,375, up from 1,093 in 2010. On August 3, 2006, a major fire destroyed approximately fifteen acres of the city in ...
, the
Yukon Delta National Wildlife Refuge The Yukon Delta National Wildlife Refuge is a United States National Wildlife Refuge covering about in southwestern Alaska. It is the second-largest National Wildlife Refuge in the country, only slightly smaller than the Arctic National Wildlife R ...
, and rarely even south to the
Shumagin Islands The Shumagin Islands (Unangan: ''Qagiiĝun''; russian: Острова Шумагина) are a group of 20 islands in the Aleutians East Borough south of the mainland of Alaska, United States, at 54°54'–55°20' North 159°15'–160°45' West. ...
. The snowy owl may breed extensively in northern Canada, largely making its home in the Arctic Archipelago. Their Canadian breeding range can include broadly
Ellesmere Island Ellesmere Island ( iu, script=Latn, Umingmak Nuna, lit=land of muskoxen; french: île d'Ellesmere) is Canada's northernmost and List of Canadian islands by area, third largest island, and the List of islands by area, tenth largest in the world. ...
up to Cape Sheridan, north coastal
Labrador , nickname = "The Big Land" , etymology = , subdivision_type = Country , subdivision_name = Canada , subdivision_type1 = Province , subdivision_name1 ...
, the northern
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 ...
, perhaps all of
Nunavut Nunavut ( , ; iu, ᓄᓇᕗᑦ , ; ) is the largest and northernmost Provinces and territories of Canada#Territories, territory of Canada. It was separated officially from the Northwest Territories on April 1, 1999, via the ''Nunavut Act'' ...
(especially the
Kivalliq Region The Kivalliq Region (; Inuktitut syllabics: ᑭᕙᓪᓕᖅ ) is an administrative region of Nunavut, Canada. It consists of the portion of the mainland to the west of Hudson Bay together with Southampton Island and Coats Island. The regional ce ...
), northeastern
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 ...
, most of northern mainland and insular
Northwest Territories The Northwest Territories (abbreviated ''NT'' or ''NWT''; french: Territoires du Nord-Ouest, formerly ''North-Western Territory'' and ''North-West Territories'' and namely shortened as ''Northwest Territory'') is a federal territory of Canada. ...
(including the
delta Delta commonly refers to: * Delta (letter) (Δ or δ), a letter of the Greek alphabet * River delta, at a river mouth * D ( NATO phonetic alphabet: "Delta") * Delta Air Lines, US * Delta variant of SARS-CoV-2 that causes COVID-19 Delta may also ...
of the Mackenzie River) and northern
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 ...
(where breeding is mostly confined to
Herschel Island Herschel Island (french: Île d'Herschel; Inuit languages: ''Qikiqtaruk'') is an island in the Beaufort Sea (part of the Arctic Ocean), which lies off the coast of Yukon in Canada, of which it is administratively a part. It is Yukon's only o ...
). Since breeding and distribution is very small, local and inconsistent in northern Europe, northern Canada and northern Alaska represent the core part of the breeding range for snowy owls along with several parts of northern and northeastern/coastal Russia.


Regular wintering range

During the wintering, many snowy owls leave the dark Arctic to migrate to regions further south. Southern limits of the regular winter range are difficult to delineate given the inconsistency of appearances south of the Arctic. Furthermore, not infrequently, many snowy owls will overwinter somewhere in the Arctic through the winter, though seldom appear to do so in the same sites where they have bred. Due in no small part to the difficulty and hazardousness of observation for biologists during these harsh times, there is very limited data on overwintering snowy owls in the tundra, including how many occur, where they winter and what their ecology is at this season. The regular wintering range has at times been thought to include Iceland, Ireland and Scotland and across northern Eurasia such as southern Scandinavia, the
Baltics The Baltic states, et, Balti riigid or the Baltic countries is a geopolitical term, which currently is used to group three countries: Estonia, Latvia, and Lithuania. All three countries are members of NATO, the European Union, the Eurozone, ...
, central Russia, southwestern
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 of ...
,
Sakhalin Sakhalin ( rus, Сахали́н, r=Sakhalín, p=səxɐˈlʲin; ja, 樺太 ''Karafuto''; zh, c=, p=Kùyèdǎo, s=库页岛, t=庫頁島; Manchu: ᠰᠠᡥᠠᠯᡳᠶᠠᠨ, ''Sahaliyan''; Orok: Бугата на̄, ''Bugata nā''; Nivkh: ...
southern
Kamchatka The Kamchatka Peninsula (russian: полуостров Камчатка, Poluostrov Kamchatka, ) is a peninsula in the Russian Far East, with an area of about . The Pacific Ocean and the Sea of Okhotsk make up the peninsula's eastern and wes ...
and, rarely, north China and sometimes the
Altai Republic The Altai Republic (; russian: Респу́блика Алта́й, Respublika Altay, ; Altai: , ''Altay Respublika''), also known as Gorno-Altai Republic, and colloquially, and primarily referred to in Russian to distinguish from the neighbour ...
. In North America, they occasionally regularly winter in the Aleutian island chain and do so broadly and with a fair amount of consistency in much of southern Canada, from
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, ...
to
Labrador , nickname = "The Big Land" , etymology = , subdivision_type = Country , subdivision_name = Canada , subdivision_type1 = Province , subdivision_name1 ...
. Recent research has indicated that snowy owls regularly winter in several of the northern
seas This is a list of seas of the World Ocean, including marginal seas, areas of water, various gulfs, bights, bays, and straits. Terminology * Ocean – the four to seven largest named bodies of water in the World Ocean, all of which have "Ocean ...
during wintertime, following the leads of
sea ice Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oce ...
as perching sites and presumably hunting mostly
seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same enviro ...
s in
polynya A polynya () is an area of open water surrounded by sea ice. It is now used as a geographical term for an area of unfrozen seawater within otherwise contiguous pack ice or fast ice. It is a loanword from the Russian полынья (), which re ...
s. In February 1886, a snowy owl landed on the rigging of the
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 ...
steamship ''Ulunda'' on the edge of the
Grand Banks of Newfoundland The Grand Banks of Newfoundland are a series of underwater plateaus south-east of the island of Newfoundland on the North American continental shelf. The Grand Banks are one of the world's richest fishing grounds, supporting Atlantic cod, swordf ...
, over from the nearest land. It was captured and later preserved at the
Nova Scotia Museum Nova Scotia Museum (NSM) is the corporate name for the 28 museums across Nova Scotia, Canada, and is part of the province's tourism infrastructure. The organization manages more than 200 historic buildings, living history sites, vessels, and speci ...
. Surprisingly, some studies have determined that after a high lemming year in North America, a higher percentage of snowy owls were using marine environments rather than inland ones.


Irruptive range

Large winter irruptions at temperate latitudes are thought to be due to good breeding conditions resulting in more juvenile migrants. These result in irruptions occurring further south than the typical snowy owl range in some years. They have been reported, as well as in all northerly states in the contiguous states, as far south as the
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 ...
,
Kentucky Kentucky ( , ), officially the Commonwealth of Kentucky, is a state in the Southeastern region of the United States and one of the states of the Upper South. It borders Illinois, Indiana, and Ohio to the north; West Virginia and Virginia 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 = ...
, nearly all the Gulf Coast of the United States, Colorado, Nevada, Texas, Utah, California and even Hawaii. In January 2009, a snowy owl appeared in Spring Hill, Tennessee, Spring Hill, Tennessee, the first reported sighting in the state since 1987. Also notable is the mass southern migration in the winter of 2011/2012, when thousands of snowy owls were spotted in various locations across the United States. This was then followed by an even larger mass southern migration in 2013/2014 with the first snowy owls seen in Florida for decades. The nature of irruptions is less well-documented in Eurasia, in part due to the paucity of this owl in the European side, but accidental occurrence, presumably during irruptions, has been described in the Mediterranean area, France, Crimea, the Caspian sea, Caspian part of Iran, Kazakhstan, northern Pakistan, northwestern India, Korea and Japan. Stragglers may too turn up as far south as the Azores and Bermuda.


Habitat

Snowy owls are one of the best known inhabitants of the open 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 moun ...
. Frequently, the earth in snowy owl breeding grounds is covered with mosses,
lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.rock Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wales ...
s. Often the species preferentially occurs in areas with some rising elevation such as hummocks, Hillock, knolls, ridges, Bank (geography), bluffs and Outcrop, rocky outcrops. Some of these rises in the tundra are created by Till, glacial deposits. The ground is usually rather dry in tundra but in some areas of the southern tundra can also be quite marshy. Not infrequently, they will also use areas of varied coastal habitat, often Mudflat, tidal flats, as a breeding site. Breeding sites are usually at low elevations, usually less than above sea level, but when breeding to the south in inland mountains, such as in Norway, they may nest at as high as . Outside the breeding season, snowy owls may occupy nearly any Open terrain, open landscape. Typically wintering sites are rather windswept with meager cover. These open areas can include Dune, coastal dunes, other coastal spots, Shore, lakeshores, islands, moorlands, steppes, meadows, prairies, other extensive grasslands and rather shrubby areas of the Subarctic. These may be favored due to their vague similarity to the flat openness of the tundra. Manmade open sites are now perhaps even more used than natural ones, often agricultural Field (agriculture), fields and rangeland, as well as large areas of Clearcutting, cleared forests. During irruption years when they are found in the northeastern United States, juveniles frequent developed areas including urban areas and golf courses, as well as the expected grasslands and Agriculture, agricultural areas that older birds primarily use. On the plains of Alberta, observed snowy owls spent 30% of their time in Crop residue, stubble-fields, 30% in summer fallow, 14% in hayfield and the remainder of the time in pasture, Grassland, natural grasslands and Slough (hydrology), sloughs. The agricultural areas, large untouched by the farmers in winter, may have had more concentrated prey than the others in Alberta. Perhaps the most consistently attractive habitat in North America to wintering snowy owls in modern times may be airports, which not only tend to have the flat, grassy characteristics of their preferred habitats but also by winter host a particular diversity of prey, both Pest (organism), pests which rely on humans as well as wildlife attracted to the extensively grassy and marshy strips that dot the large airport vicinities. For example, Logan International Airport in Massachusetts has relatively one of the most reliable annual populations known in the United States in winter. All ages spend a fair amount of their time over water in the Bering Sea, the Atlantic Ocean and even the Great Lakes, mostly on ice floes. These marine and ocean-like freshwater areas were observed to account for 22–31% of habitat used in 34 radio-tagged American snowy owls over two irruptive years, with the tagged owls occurring a mean of from the nearest land (while 35–58% used the expected preferred habitats of grassland, pasture and other agricultural land).


Behavior

Snowy owls may be active to some extent at both day, from dawn to dusk, and night. Snowy owls have been seen to be active even during the very brief winter daytime in the northern winter. During the Arctic summer, snowy owls may tend to peak in activity during the twilight that is the darkest time available given the lack of full nightfall. Reportedly, the peak time of activity during summer is between 9:00 pm and 3:00 am in Norway.Hagen, Y. (1960). ''The Snowy Owl on Hardangervidda in the Summer of 1959''. Papers of The Norwegian State Game Research. 2, No. 7. The peak time of activity for those owls that once nested on Fetlar was reported between 10:00 and 11:00 pm. According to one authority, the least active times are at noon and midnight. As days become longer near autumn in
Utqiaġvik Utqiagvik ( ik, Utqiaġvik; , , formerly known as Barrow ()) is the borough seat and largest city of the North Slope Borough in the U.S. state of Alaska. Located north of the Arctic Circle, it is one of the northernmost cities and towns in the ...
, the snowy owls in the tundra become more active around nightfall and can often be seen resting during the day, especially if it is raining. During winter in Alberta, snowy owls were tracked in the daytime, despite being also active at night (as they were deemed too difficult to track). In the study, they were most active during 8:00–10:00 am and 4:00–6:00 pm and often rested mostly from 10:00 am to 4:00 pm. The owls were perched for 98% of observed daylight and seemed to time their activity to peak times for rodents. The variation of activity is probably in correspondence with their primary prey, the
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 includ ...
s, and like them, the snowy owl may be considered Cathemerality, cathermal. This species can withstand extremely cold temperatures, having been recorded in temperatures as low as minus 62.5 Celsius, degrees Celsius with no obvious discomfort and also withstood a 5-hour exposure to minus 93 degrees Celsius but may have struggled with oxygen consumption by the end of this period. The snowy owl has perhaps the second lowest thermal conduction to the plumage on average of any bird after only the Adelie penguin (''Pygoscelis adeliae'') and rivals the best insulated mammals, such as Dall sheep (''Ovis dalli'') and
Arctic fox The Arctic fox (''Vulpes lagopus''), also known as the white fox, polar fox, or snow fox, is a small fox native to the Arctic regions of the Northern Hemisphere and common throughout the Arctic tundra biome. It is well adapted to living in ...
, as the best insulated polar creature. Presumably as many as 7 rodents would need to be eaten daily to survive an extremely cold winter's day. Adults and young both have been seen to shelter behind rocks to shield themselves from particularly harsh winds or storms. Snowy owls often spending a majority of time on the ground, perched mostly on a slight rise of elevation. It has been interpreted from the morphology of their skeletal structure (i.e. their short, broad legs) that snowy owls are not well-suited to perching extensively in trees or rocks and prefer a flat surface to sit upon. However, they may perch more so in winter though do so only mainly when hunting, at times on hummocks, fenceposts, telegraph poles by roads, Radio tower, radio and transmission towers, haystacks, chimneys and the roofs of houses and large buildings. Rocks may be used as perches at times in all seasons. Though often relatively sluggish owls, like most related species, they are capable of sudden dashing movements in various contexts. Snowy owls can walk and run quite quickly, using outstretched wings for balance if necessary. This owl flies with fairly rowing wingbeats, occasionally interrupted by gliding on stretched wings. The flight is fairly buoyant for a ''Bubo'' owl. When displaying, the male may engage in an undulating flight with interspersed wingbeats and gliding in a slight dihedral, finally dropping rather vertically to the ground. They are capable for swimming but do not usually do so. Some seen to be swimming were previously injured but young have been seen to swim into water to escape predators if they cannot fly yet. They will also drink when unfrozen water is available. Snowy owl mothers have been observed to Preening (bird), preen their young in the wild, while pairs in captivity have been observed to allopreen. In the period leading up to breeding, snowy owls switched regularly between searching (for nesting grounds) and loafing, often searching less when snow cover was less extensive. Snowy owls will fight with conspecifics in all seasons occasionally but this is relatively infrequent during breeding and rarer still during winter. Dogfights and talon interlocking may ensue if the fight between two snowy owls continues to escalate. A study determined that snowy owls are able to orient the whitest parts of their plumage towards the sun, spending about 44% of time oriented as such during sunny days and much less on cloudy days. Some authors interpret this as a presumed signal to conspecifics, but thermoregulation could also be a factor. It is known that during winter in Alberta that female snowy owls are territorial towards one another and may not leave an area for up to 80 days but males are nomadic, usually only staying 1–2 days in an area (seldom to 3–17 days). The females spent on average seven times as long in a given area than did males. During threat displays, individuals will lower the front of the body, stretch the head low and forward, with partially extended wings and feathers on the head and raise their back. If continuously threatened or cornered, the posture in the threat display may become still more contoured and, if pressed, the owl will like back and attempt to slash with its large talons. The threat displays of males are generally more emphatic than those of females. Although snowy owls have been considered as semi-colonial, they do not appear to fit this mold well. Nesting sites can be loosely clustered but this is a coincidental response to concentrated prey and each pair tends to be somewhat intolerant of each other. During winter, snowy owls are usually solitary but some Aggregation (ethology), aggregations have been recorded, especially nearer the Arctic when more narrow food selection can lead to up to 20–30 owls gathering in an area of about . Congregations were also recorded in the winter in Montana, where 31–35 owls wintered in a area, owls mostly grouped in loose aggregations of 5–10 owls each or occasionally side-by-side or about apart. In extreme cases in Utqiaġvik, the owls may have exceptionally close active nests that may be down to only apart. Juvenile males appear to be especially prone to loose associations with one another, appearing to be non-territorial and able to hunt freely in front of one another. In a area in and around Utqiaġvik, productive years may have about 54 nests while none may be found in poor years. Utqiaġvik may have about 5 owls in early summer every , have a nest spacing of and the owls territory size is about . In Churchill, Manitoba, nest spacing averaged about . In Southampton Island in a year when the owls nested there, nest spacing averaged , with the closest two apart and density per nest was . In Nunavut, densities could go from 1 owl per in a productive year to 1 owl per in a poor year and from 36 nests in a area to none at all.Manning, T. H., Höhn, E. O. & MacPherson, A. H. (1956). ''The birds of Banks Island''. National Museum of Canada Bulletin 143, Biological Series 48. Owl density on Wrangel Island in Russia was observed be a single bird each .Menyushina, I. E. (1997). "Snowy Owl (''Nyctea scandiaca'') reproduction in relation to lemming population cycles on Wrangel Island". In: ''Biology and conservation of owls of the Northern Hemisphere: 2nd International Symposium'', J. R. Duncan, D. H. Johnson and T. H. Nicholls (eds.), pp. 572–582. St. Paul: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station. The first known study of winter territories took place in Horicon Marsh where owls ranged from each. In Calgary, Alberta, mean territory size of juvenile females in winter was and adult females was . Wintering owls in central Saskatchewan were radio-monitored, determining that 11 males had an average range of , while that of 12 females was with the combined average being .


Migration

It is fair to say that the snowy owl is a partial, if fairly irregular, Bird migration, migrant, having a very broad but patchy wintering range. 1st year birds tend to disperse farther south in winter than older owls with males wintering usually somewhat more to the south than females of equivalent ages, adult females often wintering the farthest north. The snowy owl likely covers more ground than almost any other owl in movements but many complex individual variations are known in movements, and they often do not take the traditional north–south direction that might be assumed. Migratory movements appear to be somewhat more common in America than in Asia. A study of wintering owls in the
Kola Peninsula sjd, Куэлнэгк нёа̄ррк , image_name= Kola peninsula.png , image_caption= Kola Peninsula as a part of Murmansk Oblast , image_size= 300px , image_alt= , map_image= Murmansk in Russia.svg , map_caption = Location of Murmansk Oblas ...
determined that the mean date of arrival of owls was 10 November with a departure date of 13 April, covering an average of during the course of the wintering period and clustering where Ptarmigan, prey was more concentrated. Some variety of movements recorded each autumn and snowy owls winter annually in plains of
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 of ...
and Mongolia and prairies and marshlands of Canada. The Great Plains area of southern Canada host wintering snowy owls about 2 to 10 times more frequently than other areas of the continent. Some weak correlation has made with individuals having some level of fealty to certain wintering sites. Wintering snowy owls, a total of 419, recorded in Duluth, Minnesota from 1974 to 2012 would occur in larger numbers in years where Brown rat, rats were more plentiful. The amount of individual returns among 43 Duluth-wintering owls was fairly low in subsequent winters (8 for 1 year, a small handful in the next few years, and 9 in non-consecutive years). Sometimes surveys appeared to reveal hundreds of wintering snowy owls on coastal sea ice during an irruptive year. Three siblings that hatched in same nest in Cambridge Bay were recovered in drastically different spots at least a year later: one in eastern Ontario, one in
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 ...
and one in Sakhalin Island. A nestling banded in Sogn og Fjordane, Hordaland was recovered to the northeast in Finnmark. In the Logan Airport, 17 of 452 owls were recorded to return, eleven the following year, three 2 years later, and then singles variously 6, 10 and 16 years later. A banded female from Utqiaġvik was recorded to migrate over along seacoast down to Russia, returning over and covering at least in total. Another banded young female from Utqiaġvik went to the same Russian areas, returned to Utqiaġvik and then onto Victoria Island (Canada), Victoria Island, but did appear to breed, while another also covered a similar route but ended up nesting on Banks Island. Another female migrated to the Canada–United States border, then moved back to the Gulf of Alaska, then to winter in the same border areas and then finally to both Banks and Victoria Island. Snowy owls from the Canadian Arctic were monitored to have covered an average of in one autumn then covered an average of a year later. In late winter, owls from the same area were found to have covered a mean of of ground in the tundra and spent a mean of 108 days, apparently searching for a suitable nesting situation the entire time. In no fewer than 24 winters between 1882 and 1988, large numbers have occurred in Canada and the United States. These were Irruptive growth, irruption years. Record breeding irruptive years were recorded in the winters of 2011–2012 and 2014–2015. In the 1940s, it was calculated that the mean gape in time between large irruptions was 3.9 years. Southbound movements as such are much more conspicuous after peak vole years, once thought to be separated by periods of around 3–7 years. However, more extensive research has weakened the argument that irruptions are entirely food-based and the data indicates that irruptive movements are far from predictable. This is because a statewide survey in Alaska found no statewide synchrony in lemming numbers. Therefore, rather than decline of lemmings, it is the successful productivity of several pairs that plays the role, resulting in a large number of young owls that then irrupt. However, the snowy owls cannot breed in high numbers unless lemmings are widely available on the tundra.Krebs, C. J. (1993). "Are lemmings large Microtus or small reindeer? A review of lemming cycles after 25 years and future recommendations for future work". In: ''The biology of lemmings'', N. C. Stenseth and R. Ims (eds.), pp. 247–260. London: Academic Press for the Linnean Society of London. This connection of irruptions to high years of productivity was confirmed in a study by Robillard et al. (2016). About 90% of the snowy owls seen in irruptive years from 1991 to 2016 that were ageable were identified as juveniles.


Hunting


Hunting techniques

Snowy owls may hunt at nearly at any time of the day or night, but may not attempt to do so during particularly severe weather. During the summer solstice, the owls appear to hunt during "theoretical nightfall". Night-vision devices have allowed biologists to observe that snowy owls hunt quite often during the extended nighttime during the northern winter. Prey are both taken and eaten on the ground. Snowy owls, like other carnivorous birds, often swallow their small prey whole. Strong stomach juices digest the flesh, while the indigestible bones, teeth, fur, and feathers are compacted into oval pellets that the bird regurgitates 18 to 24 hours after feeding. Regurgitation often takes place at regular perches, where dozens of pellets may be found. Biologists frequently examine these pellets to determine the quantity and types of prey the birds have eaten. When large prey are eaten in small pieces, pellets will not be produced. Larger prey is often torn apart, sometimes include removal of the head, with the large muscles, such as the humerus or Thorax, breast, typically eaten first. The scattering of remains that results from the increment feeding on larger prey is thought to result in under-identification of them compared to smaller prey items. The aptitude for hunting by day, hunting from the ground and hunting in almost always completely open and treeless areas are the primary ways in which the snowy owl differs in hunting from other ''Bubo'' owls. Otherwise, the hunting habits are similar.Paul Johnsgard, Johnsgard, P. A. (1988)
''North American owls: biology and natural history''
Smithsonian Institution.
It is thought, due to their less refined hearing compared to other owls, prey is usually perceived via vision and movement. Experiments indicate that snowy owls can detect prey from as far as away. Snowy owls generally use a rise or, occasionally, a perch while hunting. 88% of observed 34 hunts in Utqiaġvik were undertaken from an elevated watch-site (56% mounds or rises, 37% telephone poles). Their hunting style may recall that of Buteo, buzzards, with the hunting owl sitting rather low and perching immobile for a long spell. Although their usual flight is a slow, deliberate downbeat on the broad, fingered wings, when prey is detected from their perch, flight may undertaken with a sudden, surprisingly quick accelerated style with interspersed wing beats. In Utqiaġvik, snowy owls may most frequently engage in a brief pursuit hunting style. In high winds capable of keeping their bulk aloft, snowy owls may too engage in a brief Levitation, hovering flight before dropping onto prey. When hunting fish, apparently, some snowy owls will hover in a style reminiscent of the osprey (''Pandion haliaetus''), although in at least one other case a snowy owl was observed to capture fish by lying on its belly upon a rock by a fishing hole.Audubon, J. J. (1840). ''The Birds of America''. Dover Publications, Inc., New York, NY, USA. A dashing stoop or pounce down onto their prey, ending in a high-impact "wallop", is fairly commonly recorded. Another common technique is the "sweep", wherein they fly by and grasp the prey while continuing to fly. In winter, snowy owls have been shown to be able to "snow plunge" to capture prey in the Subnivean climate, subnivean zone, under at least of snow. Perhaps least frequently, snowy owls may pursue their prey on foot, in doing so never taking wing. Snowy owls have been known to capture Bird migration, night-migrating passerines and shorebirds, sometimes perhaps on the wing, as well as large and/or Bird of prey, potentially dangerous birds that were caught in air by snowy owls during daylight. On the wing pursuits against other various other carnivorous birds are sometimes undertaken as well to Kleptoparasitism, kleptoparasitize the prey caught by the other birds. Few variations of hunting technique were observed in winter observations from Alberta, almost all of the hunts being with the sit-and-wait method (also known as still-hunts). Adult females in Alberta had a considerably better hunting rate than juvenile females. Much as in Alberta, in Syracuse, New York, 90% of 51 hunts were still-hunting, with the sweep variant used after perch departure in 31% of hunts and the pounce method in 45% of hunts. The Syracuse-wintering owls used tall perches, a mixture of manmade objects and trees of around high, in nearly 61% of hunts, while nearly 14% were from low perches (i.e. fence-posts, snow banks and scrap piles) about half as high as the tall perches and started from a ground position nearly 10% of the time.Winter, R. E. (2016)
''Hunting Behaviors and Foraging Success of Winter Irruptive Snowy Owls in New York''
. SUNY College of Environmental Science and Forestry, Thesis.
In Sweden, males hunted from a perch more so than did females and adults both focused on significantly smaller prey (small
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) and may have had more success hunting than juvenile snowy owls. Some snowy owls can survive a fast for up to about 40 days off of Fatty acid metabolism, fat reserves. These owls were found to have extremely thick Subcutaneous tissue, subcutaneous fat deposits of and it is likely owls that overwinter in the Arctic rely heavily on these to survive during this scarce time, in combination with lethargic, energy-conserving behavior. Snowy owls may not infrequently exploit prey inadvertently provided or compromised by human activities, including ducks injured by Hunting, duck hunters, Red phalarope, birds maimed by Antenna (radio), antenna wires, various animals caught in human Trapping, traps and traplines as well as Domestication of animals, domestic or wild prey being bred or farmed by humans in enclosures. A wide variety of accrued reports show that the snowy owl that Scavenger, scavenging on
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 ...
is not uncommon (despite having once been thought to be very rare in all owls), including instances of reindeer (''Rangifer tarandus'') body parts brought to nests and owls following
polar bear The polar bear (''Ursus maritimus'') is a hypercarnivorous bear whose native range lies largely within the Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the largest extant bear specie ...
s to secondarily feed on their kills. Even huge marine mammals such as walrus (''Odobenus rosmarus'') and whales can be fed upon by these owls when the opportunity occurs. Snowy owls produce a Pellet (ornithology), pellet that in different areas averages a median of about , averaging up to in length as in Europe.


Prey spectrum

The snowy owl is primarily a hunter of
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. Most especially, they often live off of the northerly
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 includ ...
s. Sometimes other similar rodents like voles can also be found frequently in the snowy owl's foods. It is r/K selection theory, R-selected, meaning that it is an opportunistic breeder capable of taking advantage of increases in prey numbers and diversity, despite its apparent specialization. Birds are commonly taken as well, and may regularly include passerines, northern
seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same enviro ...
s, ptarmigan and ducks, among others. Sometimes infrequent consumption of other prey such as beetles, crustaceans and occasionally amphibians and fish is reported (of these only fish are known to have been identified to prey species). All told, more than 200 prey species have been known to be taken by snowy owls around the world. Generally, like other large owls (including even bigger owls like the
Eurasian eagle-owl The Eurasian eagle-owl (''Bubo bubo'') is a species of eagle-owl that resides in much of Palearctic, 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, ...
), prey selection tends toward quite small prey, usually small
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, but they can alternate freely with prey that is much larger than typical given the opportunity or even bigger than themselves, including relatively large mammals and several types of large bird of almost any age.Marti, C. D., Korpimäki, E., & Jaksić, F. M. (1993). "Trophic structure of raptor communities: a three-continent comparison and synthesis". In ''Current ornithology'', pp. 47–137. Springer, Boston, MA. One study estimated for the biomes of
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 Canada, mean prey sizes for snowy owls were , in western United States, western North America, the mean prey size was and in eastern United States, eastern North America was , while the mean prey size in northern Fennoscandia was similar (at ). The mean number of prey species for snowy owls per biome ranged from 12 to 28. The opportunistic nature of snowy owls has long been known during their primarily winter observed feeding habits (leading to their unpopular nature and frequent persecution well into the 20th century).


Summer diet

The snowy owl's biology is closely tied to the availability of
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 includ ...
s. These herbivorous rodents are largish members of the vole clan that are the predominant mammal of the tundra ecosystem alongside the reindeer and probably make up the majority of the mammalian biomass of the ecosystem. Lemmings are key architects of the soil, Topography, microtopography and plant life of the entire tundra. In the American lower Arctic areas, True lemming, brown lemming of the ''Lemmus'' genus are predominant and tend to be found in lower, wetter habitats (feeding by preference on grasses sedges and mosses) while collared lemmings of the ''Dicrostonyx'' genus were in more arid, often higher elevation habitats with heathland and ate by preference willow Leaf, leaves and forbs. The southerly brown lemmings behave differently than more northern collared lemming type, increasing almost limitlessly within preferred habitat whereas the collared type tends to spread to suboptimal habitats and therefore does not appear reach the high regional densities of the brown. Authorities now generally agree that there appears to be no synchrony between the brown and collared lemmings and the feeding access of snowy owls is irregular as a result, but snowy owls can likely alternate between the two lemming types as one or the other increases as they nomadically use different parts of the Arctic. It is possible that the rare coincidental mutual peak of both lemming types within a year results in the erratic high productivity that results in irruptions. Within individual Arctic lemming species, historically, populations can vary in rough 4- to 5-year trends. As a result, in areas such as Banks Island, the breeding rate of snowy owls can vary within a decade by about tenfold. Weights of lemmings taken can range from on Baffin Island, while those taken in Utqiaġvik averaged in female and male lemming, respectively. It was estimated based on captive daily food intake that a snowy owl may consume about of lemmings a day, though other estimates using voles show a daily need for about . On Southampton Island, 97% of the diet was lemmings. A very similar number of lemmings (nearly 100%) were found over 25 years of study in Utqiaġvik, amongst 42,177 cumulative prey items. Of 76 lemmings that could be identified to sex at a Hoarding (animal behavior), cache, male lemmings were found in the cache twice as often as female lemmings. While initial findings indicated on
Wrangel Island Wrangel Island ( rus, О́стров Вра́нгеля, r=Ostrov Vrangelya, p=ˈostrəf ˈvrangʲɪlʲə; ckt, Умӄиԓир, translit=Umqiḷir) is an island of the Chukotka Autonomous Okrug, Russia. It is the 91st largest island in the w ...
that female lemmings outnumbered males in prey remains, to the contrary osteology indicated that, like Utqiaġvik, males were more often taken. However, the slightly larger, slower-moving females may be preferred when available.Krechmar, A.V. & Dorogoy, I.V . (1981). "Snowy Owl (''Nyctea scandiaca'')". In: ''Ecology of mammals and birds in Wrangel Island''. Vladivostok: DVNZ AN SSSR: pp. 56–81. In some areas, snowy owls can breed where lemmings are uncommon to essentially absent. Even in Utqiaġvik, where the diet is quite homogenously based in lemmings, the hatching of passerines, shorebirds and waterfowl can provide a key resource when lemmings are not found regularly and may be the only means by which the young can survive at such lean times. In the Nome, Alaska area, the locally nesting snowy owls reportedly switched from lemmings to ptarmigans when the latter's chicks hatched. A somewhat varying diet was also reported in Prince of Wales Island (Nunavut), Prince of Wales Island, Nunavut where 78.3% of the biomass was lemmings, with 17.8% from waterfowl, 3.3% from Stoat, weasel and about 1% from other birds. In Fennoscandia, among 2,700 prey items only a third were Norway lemmings (''Lemmus lemmus'') and a majority were voles at 50.6%, probably largely the tundra vole (''Microtus oeconomus''). A more detailed glance at Lapland (Finland), Finnish Lapland showed that amongst 2,062 prey items, 32.5% of the foods were Norway lemmings (though in some years the balance could range up to 58.1%), 28% were grey red-backed voles (''Myodes rufocanus'') and 12.6% were tundra voles, with birds constituting a very small amount of the prey balance (1.1%). In northern Sweden, a more homogenous diet was found with the Norway lemming constituting about 90% of the foods. In the Yamal Peninsula, 40% of the diet was collared lemmings, 34% were Siberian brown lemming (''Lemmus sibiricus''), 13% were ''Microtus'' voles and Willow ptarmigan, ptarmigan and ducks both constituting 8% and with other birds making up much of the remaining balance. In some parts of the tundra, snowy owls may opportunistically prey upon Arctic ground squirrels (''Spermophilus parryii''). In the Hooper Bay area (much farther south than they usually nest), various rodents, in highland areas, and waterfowl, in marshland, were taken while breeding. When historically breeding on
Fetlar Fetlar ( sco, Fetlar) is one of the North Isles of Shetland, Scotland, with a usually resident population of 61 at the time of the 2011 census. Its main settlement is Houbie on the south coast, home to the Fetlar Interpretive Centre. Fetlar i ...
in Shetland, the main prey for snowy owls was European rabbits (''Oryctolagus cuniculus''), Eurasian oystercatcher (''Haematopus ostralegus''), parasitic jaegers (''Stercorarius parasiticus'') and Eurasian whimbrel (''Numenius phaeopus''), in roughly that order, followed by other bird species with most (rabbits and secondary birds) prey taken as adults but for the oystercatchers and jaegers which were taken largely as fully grown but only recently fledged juveniles. 22–26% of oystercatcher and jaeger young in the island were estimated to be taken by snowy owls. Bird predation by nesting snowy owls is highly opportunistic. Willow ptarmigan, Willow (''Lagopus lagopus'') and rock ptarmigan (''Lagopus muta'') of any age are often fairly regular in the diet of breeding snowy owls but they cannot be said to particularly specialize on these. Evidence was found in the Yamal Peninsula that the snowy owls became the primary predator of willow ptarmigan and that the predation was so frequent, it may have been the cause of the change of their habitat usage to willow thickets by the local ptarmigan. The reliance on ptarmigan has caused some conservation trickle-down concern for the owls because ptarmigan are hunted in large numbers, with the hunters of Norway permitted to cull up to 30% of the regional population. In North America, avian prey on the breeding ground regularly varies from small passerines like snow buntings (''Plectrophenax nivalis'') and Lapland longspurs (''Calcarius lapponicus'') to large waterfowl like King eider, king (''Somateria spectabilis'') and common eider (''Somateria mollissima'') and usually the goslings but also occasionally adults of geese such as Brant (goose), brants (''Branta bernicla''), snow geese (''Anser caerulescens'') and cackling geese (''Branta hutchinsii''). Drake eiders of often similar size to the owls themselves are not infrequently the largest prey amongst remains around the nest mound. One nest had the bodies of all eiders that attempting to nest in the vicinity around it.Dorogoy, I.V . (1987). ''Ecology of small mammal predators in Wrangel Island and their role in the dynamics of lemming numbers''. Vladivostok: DVO AN SSSR. (In Russian). The threatened and declining Steller's eider (''Polysticta stelleri'') when nesting in the Utqiaġvik area would appear to avoid the vicinity of snowy owl nests when selecting their own nesting sites due to the predation risk. Intermediately sized
seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same enviro ...
s are often focused on in lieu of available lemmings. Foods were studied intensively in Iceland. Among 257 prey items found with a total prey mass of , birds made up 95% of the diet. The leading prey were adult rock ptarmigan, at 29.6% by number and 55.4% by biomass and adult European golden plover (''Pluvialis apricaria''), at 10.5% by number and 7.2% biomass. The rest of the balance was largely other shorebirds, which were taken slightly more often as chicks than adults. Pink-footed geese (''Anser fabalis'') were taken in equal number as goslings and adults, with respectively estimated average weights at these ages of . On the isle of Agattu, the diet consisted entirely of birds, as there are no mammals found there. The much favored food in Agattu was the ancient murrelet (''Synthliboramphus antiquus''), at 68.4% of the biomass and 46% by number, while the secondary prey were followed numerically by smaller Leach's storm-petrels (''Oceanodroma leucorhoa'') (20.8%) and Lapland longspurs (10%) and in biomass by smallish ducks, the green-winged teal (''Anas carolinensis'') and harlequin duck (''Histrionicus histrionicus'') (13.4% biomass collectively). In the Murman Coast of Russia, also in the absence of lemmings,
seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same enviro ...
s formed the largest part of the diet.Krasnov, Y. (1985). ''To the biology of the Snowy Owl in the Eastern Murman. Birds of Prey and Owls in the Nature Reserves of the Russian Federation''. TSNIL GLAVOKHOTA, pp. 110–116.


Winter diet

On the wintering grounds, mammals often predominate in the snowy owl's food inland doing so less in coastal areas. Overall wintering snowy owls eat more diverse foods they do whilst breeding, furthermore coastal wintering snowy owls had more diverse diets than inland ones. As in summer, moderately sized
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 such as Eurasian teal, teal, northern pintail (''Anas acuta'') and numerous alcids and the like are often focused on when hunting birds. The diet in 62 pellets, amongst at least 75 prey items, from coastal Oregon showed the main foods as black rat (''Rattus rattus'') (at an estimated 40%), red phalarope (''Phalaropus fulicarius'') (31%) and bufflehead (''Bucephala albeola'') (19%). Witnessed attacks were mostly upon buffleheads in Oregon. In coastal 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, ...
, the diet among 139 prey items was 100% avian. The predominant prey were
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, mostly snatched directly from surface of the water and largely weighing , i.e. buffleheads (at 24% by number and 17.4% by biomass of foods) and horned grebes (''Podiceps auritus'') (at 34.9% by number and 24.6% by biomass), followed by variously other water birds, often the slightly larger species of glaucous-winged gull (''Larus glaucescens'') and the American wigeon (''Mareca americana''). A different study of this area also showed the predominance of ducks and other water birds to wintering snowy owls here, although Townsend's vole (''Microtus townsendii'' ) (10.65%) and snowshoe hare (''Lepus americanus'') (5.7%) were also notably in a sample of 122 prey items. During winter, snowy owls consume more strongly nocturnal prey than lemmings such as ''Peromyscus'' mice and northern pocket gophers (''Thomomys talpoides''). In southern Alberta, 248 prey items were found with North American deermouse (''Peromyscus maniculatus''), at 54.8% by number, and meadow voles (''Microtus pennsylvanica''), at 27% by number, as the main foods of snowy owls over two years. Other prey in Alberta were grey partridge (''Perdix perdix'') (at 5.79% of total), White-tailed jackrabbit, jackrabbits, weasels and Short-eared owl, owls. Richardson's ground squirrels (''Urocitellus richardsonii'') were consumed heavily in the Alberta study in a brief converged times of hibernation emergence and overwintering snowy owls. The sexual dimorphism in prey selection was also studied here, with male owls mainly focusing exclusively on the small rodents, females also took the same rodents but supplemented the diet with all alternate and larger prey. Overall, the meadow and montane voles (''Microtus montanus'') constituted 99% of over 4500 prey items in Montana. In Horicon Marsh in winter, 78% of the diet was meadow vole, with 14% being muskrats (''Ondatra zibethicus''), 6% ducks and smaller balances of rats and other birds. Snowy owls found in Michigan took meadow voles for 86% of the diet, white-footed mouse (''Peromyscus leucopus'') for 10.3% and northern short-tailed shrew (''Blarina brevicauda'') for 3.2%. Of 127 stomachs in New England in four irruptive winters from 1927 to 1942, of 155 prey items, 24.5% were brown rats, 11.6% were meadow voles and 10.3% were dovekie (''Alle alle''), with a smaller balance of snowshoe hare and birds from snow buntings to American black ducks (''Anas rubripes''). During the same years, stomach contents in Ontario included 40 identified prey items, led by brown rats (20%), white-footed mice (17.5%) and meadow voles (15%); of 81 prey items from Pennsylvania in 60 stomachs that were not empty, eastern cottontail (''Sylvilagus floridanus'') (32%), meadow vole (11.1%), Chicken, domestic chicken (''Gallus gallus domesticus'') (11.1%) and northern bobwhite (''Colinus virginianus'') (5%) were the most often identified prey species. Introduced common pheasants were found to be somewhat more vulnerable than native American gamebirds like ruffed grouse due to their tendency to crouch rather than flush when approached by a flighted predator like the snowy owl in a Glade (ecology), glade or field. Some snowy owls wintering on Cliffed coast, rocky coasts and Jetty, jetties were known in New England to live almost entirely off of purple sandpipers (''Calidris maritima''). The availability of brown rats may draw snowy owls to seemingly unattractive settings such as Landfill, garbage dumps and under bridges. Meanwhile, snowy owls wintering in Lowell, Massachusetts were seen to live largely off of rock doves (''Columba livia'') caught off of buildings. Of 87 prey from stomachs in Maine, 35% were Rattus, rats or mice, 20% were snowshoe hares and 10% were passerines. A small study of 20 prey items in an irruptive winter in Kansas found that 35% of the prey were red-winged blackbird (''Agelaius phoeniceus''), 15% prairie voles (''Microtus ochrogaster'') and 10% each by American coot (''Fulica americana'') and hispid cotton rats (''Sigmodon hispidus''). On the isle of St. Kilda, Scotland, St. Kilda, 24 pellets were found for non-breeding snowy owls that stayed through the early summer. Of 46 prey items, the St Kilda field mouse (''Apodemus sylvaticus hirtensis'') was predominant by number at 69.6% but constituted 16.8% of biomass while adult Atlantic puffin (''Fratercula arctica'') constituted 63.5% of the prey biomass and 26% by number (rest of the balance being juvenile puffins and great skuas (''Stercorarius skua'')).Miles, W. T. S., & Money, S. (2008). ''Behaviour and diet of non-breeding Snowy Owls on St Kilda''. Scottish Birds, 28, 11. The main subspecies of wood mouse was similarly dominant in the diet within County Mayo, Ireland and were presumably snatched at night due to their strict nocturnality. In Knockando, Moray, Knockando, the winter diet was led by European rabbits (40.1%), red grouse (''Lagopus lagopus scotica'') (26.4%) and adult mountain hare (''Lepus timidus'') (20.9%) (in 156 pellets); in Ben Macdui, the diet was led by rock ptarmigan (72.3%), field voles (''Microtus agrestis'') and juvenile mountain hare (8.5%) (33 pellets); in Cabrach, the diet was led by red grouse (40%), mountain hare (20%) and European rabbit (15%) (16 pellets). Among 110 prey items found for snowy owls found wintering during irruption in southern Finland, all but 1 prey item were field voles (the only other prey being a single long-tailed duck (''Clangula hyemalis'')). Far to the east, wintering owls in the Irkutsky District were found to subsist mostly on narrow-headed voles (''Microtus gregalis'').Maleev, V.G. & Popov, V. V. (2007). ''Birds of forest-steppes of the Upper Angara river basin''. Irkutsk. In a wintering population in Kurgaldga Nature Reserve of Kazakhstan, the main foods were grey red-backed voles at 47.4%, winter white dwarf hamster (''Phodopus sungorus'') at 18.4%, steppe pika (''Ochotona pusilla'') at 7.9%, muskrat at 7.9%, Eurasian skylark (''Alauda arvensis'') at 7.9%, grey partridge at 5.3%, and both steppe polecat (''Mustela eversmanii'') and yellowhammer (''Emberiza citrinella'') at 2.6%. On the Kuril Islands, wintering snowy owls main foods were reported as tundra voles, brown rats, ermines and whimbrel, in roughly that order. Data from the Logan Airport in over 6,000 pellets shows that meadow vole and brown rat predominated the diet in the area, supplanted by assorted birds both small and large. American black ducks were primarily taken among bird species with other birds taken here including relatively large and diverse species Canada geese (''Branta canadensis''), brants, American herring gulls (''Larus argentatus''), double-crested cormorant (''Phalacrocorax auritus''), great blue heron (''Ardea herodias''), in addition to some formidable mammals such as Cat, house cat, American mink (''Mustela vision''), and striped skunk (''Mephitis mephitis''). Given the large size of some of this prey, it can be projected that the snowy owl can kill adult prey of around twice their own weight (i.e. geese, cats, skunks, etc.). Other large prey is sometimes taken by snowy owls, all roughly within the weight range often include adults of large leporids such as Arctic hare (''Lepus arcticus''), Alaskan hare (''Lepus othus''), mountain hare and white-tailed jackrabbits (''Lepus townsendii''). As well as several species of geese, probable cygnets of Tundra swan, Bewick's swans (''Cygnus columbianus bewickii'') as well as adults of the following: western capercaillie (''Tetrao urogallus'') (of both sexes), greater sage-grouse (''Centrocercus urophasianus'') and yellow-billed loons (''Gavia adamsii''). At the other end of the scale, the snowy owl has been known to take birds down to size of dark-eyed juncos (''Junco hyemalis'') and mammals down the size of common shrews (''Sorex araneus'').Dunning, Jr., J. B. (1993). ''CRC handbook of avian body masses''. CRC Press, Boca Raton, FL. Fish are rarely taken anywhere but the snowy owl has been known to prey upon Arctic char (''Salvelinus alpinus'') and lake trout (''Salvelinus namaycush'').Bailey, A. M. (1948). ''Birds of Arctic Alaska''. Colorado Mus. Nat. Hist., Popular Ser., 8.


Interspecific predatory relationships

The snowy owl is in many ways a very unique owl and differs from other species of owl in its ecological niche. Only one other owl, the
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 ...
, is known to breed in the High Arctic. However, the snowy owl shares its primary prey, the True lemming, brown and collared lemmings, with a number of other avian predators. In sometimes differing parts of the Arctic, competing predators for lemmings are, in addition to short-eared owls, pomarine jaegers (''Stercorarius pomarinus''), long-tailed jaegers (''Stercorarius longicaudus''), rough-legged buzzards (''Buteo lagopus''), hen harriers (''Circus cyaenus''), northern harriers (''Circus hudsonius'') and generally less specialized gyrfalcons (''Falco rusticollis''), peregrine falcons (''Falco peregrinus''), glaucous gulls (''Larus hypoboreus'') and common ravens (''Corvus corax''). Certain carnivorous mammals, especially the
Arctic fox The Arctic fox (''Vulpes lagopus''), also known as the white fox, polar fox, or snow fox, is a small fox native to the Arctic regions of the Northern Hemisphere and common throughout the Arctic tundra biome. It is well adapted to living in ...
and, in this region, the Stoat, ermine, are also specialized to hunt lemmings. Most of the lemming predators are intolerant of the competition given the scattered nature of lemming populations and will displace and/or kill one another given the chance. However, given the need to conserve energy in the extreme environment, the predators may react passively to one another. When unusually breeding south in the Subarctic such as western Alaska, Scandinavia and central Russia, the number of predators with which the snowy owls are obligated to share prey and compete with may be too numerous to name. The taking of the young and eggs of snowy owls has been committed by a large number of predators: Buteo, hawks and eagles, the northern Skua, jaegers, peregrine and gyrfalcons, glaucous gulls, common ravens, Arctic wolf, Arctic wolves (''Canis lupus arctos''),
polar bear The polar bear (''Ursus maritimus'') is a hypercarnivorous bear whose native range lies largely within the Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the largest extant bear specie ...
s, brown bears (''Ursus arctos''), wolverines (''Gulo gulo'') and perhaps especially the Arctic fox. Adult snowy owls on the breeding grounds are far less vulnerable and can be justifiably qualified as an apex predator. Instances of killing of adult snowy owls on the breeding grounds have been witnessed to be committed by a pair of pomarine jaegers on an incubating adult female snowy owl (possibly merely a competitive attack as she was left uneaten) and by an Arctic fox that killed an adult male snowy owl. When it goes south to winter outside of the Arctic, the snowy owl has a potential to interact with a number of additional predators. By necessity, it shares its wintertime diverse prey with a number of formidable predators. These are known to include their cousins, the
great horned owl 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 native to the Americas. It is an extrem ...
and the
Eurasian eagle-owl The Eurasian eagle-owl (''Bubo bubo'') is a species of eagle-owl that resides in much of Palearctic, 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, ...
. They are relieved of heavy competition from the related species by differing temporal activity, i.e. being more likely to actively hunt in daytime, and by habitat, using rather more open (quite often nearly treeless) habitats than them. During a study of wintering snowy owls in Saskatchewan, the authors indicated that the snowy owls may avoid areas inhabited and defended by great horned owls. Although they usually occurred here outside of an radius of central great horned owl ranges, they did not avoid the radius and different habitat usage may be a dictating factor.Chang, A. M. (2017)
Habitat use, movement patterns, and body condition of male and female Snowy Owls (''Bubo scandiacus'') in winter
Doctoral dissertation, University of Saskatchewan.
Given their mildly slighter size, it is unlikely that great horned owls (unlike the larger eagle-owl) would regularly dominate snowy owls in interactions and either species may give way to other depending on the size and disposition of the owls involved. Little study has been undertaken into the Trophic level, trophic competition of snowy owls with other predators during winter and, due to their scarcity, few predators are likely to expel much energy on competitive interactions with them, although many other predators will engage in anti-predator Mobbing (animal behavior), mobbing of snowy owls. Largely in winter, snowy owls have been the victim of a number of larger avian predators, though attacks are likely to be singular and rare. Instances of predation on snowy owls are known to have been committed several times in winter only by
Eurasian eagle-owl The Eurasian eagle-owl (''Bubo bubo'') is a species of eagle-owl that resides in much of Palearctic, 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, ...
s. Additionally, golden eagles (''Aquila chrysaetos'') have been known to prey on snowy owls as well as all northern sea eagles: the Bald eagle, bald (''Haliaeetus leucocephalus''), White-tailed eagle, white-tailed (''Haliaeetus albicilla'') and Steller's sea eagles (''Haliaeetus pelagicus''). Snowy owls are also sometimes killed by birds that are mobbing them. In one instance, a peregrine falcon killed a snowy owl in a stoop after the owl had itself killed a fledgling falcon. Anecdotal report indicate predation by gyrfalcons (on snowy owls of unknown age and condition) but it was possibly also an act of mobbing.Heggøy, O., & Øien, I. J. (2014)
''Conservation status of birds of prey and owls in Norway''
NOF/BirdLife Norway-Report, 1, 1–129.
In another, a huge Flock (birds), throng of Arctic terns (''Sterna paradisaea'') relentlessly swarmed and attacked a snowy owl until it meet its demise. Almost certainly more often than being victim of other predators, snowy owls are known to dominate, kill and feed on a large diversity of other predators. Snowy owls, much like other ''Bubo'' owls, will opportunistically kill other birds of prey and predators. Although they will readily plunder the nests of other raptorial birds given the opportunity, most predations are on full-grown raptorial birds during winter due to the scarcity of raptor nests in the open tundra. In addition, most competing predators of the Arctic, excepting the very large mammals, are probably vulnerable to a hungry snowy owl. In data from the Logan Airport alone over different winters, the snowy owls were observed to have preyed upon an impressive diversity of other raptorial birds: rough-legged buzzards, American kestrels (''Falco sparverius''), peregrine falcons, barn owls, other snowy owls, barred owls (''Strix varia''), northern saw-whet owls (''Aegolius acadicus'') 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. While owls are likely encountered during corresponding hunting times, it is likely that the swift falcons are usually ambushed at night (much as other ''Bubo'' owls will do). In both the tundra and the wintering ground, there are several accounts of predation by snowy owls on short-eared owls. In addition, snowy owls have been known to prey on northern harriers, northern goshawks (''Accipiter gentilis'') and gyrfalcons. In a few cases, both juvenile and adult
Arctic fox The Arctic fox (''Vulpes lagopus''), also known as the white fox, polar fox, or snow fox, is a small fox native to the Arctic regions of the Northern Hemisphere and common throughout the Arctic tundra biome. It is well adapted to living in ...
es have been known to fall prey to snowy owls. A wintering snowy owl in Saskatchewan was observed to have preyed on an adult red fox (''Vulpes vulpes''). Predation by snowy owls on red foxes was also reported in the Irkutsky District of Russia. With an adult weight around (and far from defenseless), red fox may be the largest known prey known for snowy owls. Besides aforementioned predation on domestic cats and skunks, several members of the weasel family, both small and relatively large, are known to be opportunistically hunted by snowy owls. As a result of its potential predator status, the snowy owl is frequently mobbed at all times of the year by other predatory birds, including fierce dive-bombing by several of the northern falcons on the wintering grounds, including even by the relatively tiny but fierce and very agile Merlin (bird), merlin (''Falco columbarius''). The much bulkier snowy owls cannot match the speed and flight ability of a falcon, and may be almost relentlessly tormented by some birds such as peregrines.


Breeding


Pair bond and breeding territory

In Utqiaġvik, of 239 recorded breeding attempts, 232 were monogamous, the other 7 Bigamy, social bigamy. On Baffin Island, 1 male bred with 2 females and sired 11 total fledged young. Another case of bigamy was reported in Norway where the 2 females bred to one male were apart in nest site location. On Feltar from 1967 to 1975, a male breed with two females, 1 younger and was possibly his own Incest, daughter. In the Feltar males first time breeding with both females, he did not bring food to the younger female. However, when older female disappeared the following year, the male and younger female producing 4 young, but disappeared the subsequent year altogether in 1975. There are also unconfirmed cases of polyandry, with 1 female being fed by 2 males. Snowy owls can breed once per year but when food is scarce many do not even attempt to breed. Despite frequent wandering in search of food, they generally adhere more so than to a strict breeding season than
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 nesting in the tundra. 9 radio-tagged female snowy owls about Bylot Island were tracked to study how pre-laying snow cover effects their searching behavior for breeding area. These tracked females searched an average of 36 days and covered an average of . It is thought that the male and female mutually find an attractive breeding spot independently and converge. The breeding territory normally averages about as in both Baffin Island and
Ellesmere Island Ellesmere Island ( iu, script=Latn, Umingmak Nuna, lit=land of muskoxen; french: île d'Ellesmere) is Canada's northernmost and List of Canadian islands by area, third largest island, and the List of islands by area, tenth largest in the world. ...
but varies in accordance to abundance of food and density of owls. Nesting territories average at Baffin island in the range of during poor lemming years. Nesting territories may up to on Southampton Island and had a mean distance of between active nests. In Utqiaġvik, nesting pairs can vary from none to at least 7 and the territories average , with mean nest distances of . In the Norwegian highlands, nesting occurs only at times of plenty distances of between nests, averaging . Males marks territory with singing and display flights and likely always initiates. During the display, he engages in exaggerated wing beats with a shallow undulating and bouncy courtship flight with wings held in a Dihedral (aeronautics), dihedral. He often drops to the ground but then flies again to only glide gently back down. Overall, the flight is somewhat reminiscent of the flight of a moth. Females will answer her mate with her song during courtship. While courting, the male often also carries a lemming in his bill, then bows with cocked tail, similarly as in related owls (seldom displaying some other prey like snow buntings). He then flaps his wings open in an emphatic manner, with the ground display being relatively brief (about 5 minutes). The female may possibly refuse to breed if ritual not performed. A possible courtship was engaged in by a male in southern Saskatchewan when a female was sighted. On Southampton Island, at least 20 males observed in late May in a "lemming year". Nesting territory defense displays, not highly different from courtship displays, includes undulating flight and stiffly raised wings with bouts of exaggerated, delayed wing beats, looking like enormous white moths exposing their white wings under the sun. At times, competing males will interlock claws in mid-air. Territorial and nuptial displays are followed by a ground display by the male with the wings arched up in an "angel" posture, visible for well over a mile.


Nest sites

Most individuals arrive at the nest site by April or May with a few overwintering arctic exceptions. Males advertises potential nest sites to his mate by scratching the ground and spreading his wings over it. The nest is usually a shallow depression on a windswept eminence in the open tundra. There seems to be a variety of qualifiers for appropriate nest sites. The nest site is typically snow-free and dry relative to the surrounding environment, usually with a good view of the surrounding landscape. The nest may be made of ridges, Mound, elevated mounds, high polygons, hummocks, hills, man-made mounds and occasionally Outcrop, rocky outcrops. If covered with vegetation, taller plants that may obstruct view are plucked away sometimes. The nest sites are often long-established and naturally created by the freeze-thaw process of the tundra. Bar (river morphology), Gravel bars may be used as well. The female may take the most active role in the nest's condition of any owl species. No owl build their own nests but female snowy owls take about three days constructing a scrape, digging with her claws and rotating until a fairly circular bowl is formed. She will still not construct or add foreign materials to the nest (despite some circumstantial evidence of moss and grass from outside the nest mound being found). In two separate cases in Utqiaġvik, two separate females dug out a second scrape to the side and below the main nests and appeared to have called all chicks to the more secluded nest to ride out severe weather until the skies cleared. The Utqiaġvik nest scrapes averaged in 91 with a mean depth of while the scrapes were smaller in Hooper Bay, reportedly diameter and in depth. Occasionally, in the lower tundra, snowy owls may too use old nests of rough-legged buzzards as well as abandoned eagle nests. Unlike other northerly breeding raptorial birds, the snowy owl is not known to nest on cliffs and the like, so do not enter into direct competition with eagles, falcons, ravens or other ''Bubo'' owls when nesting to the relative south. The area of nest mound often has a relatively rich plant life which attract the lemmings, which may tunnel right under and around the owl's nest. Goose, Geese, ducks and shorebirds of several species known to gain incidental protection by nesting close to snowy owls. Conversely, the snowy owls will sometimes kill and eat both young and adults of these birds, which implies a trade-off in the benefits.


Eggs

Egg-laying normally begins during early May to the first 10 days of June. Late thaws are harmful to them since they allow too little time for the full breeding process, with particularly importance given to good food supply in May for adults, even more so apparently than food supply in July when young are being fed. Late nests are possible cases of inexperienced pairs, low food supplies, bigamy or even replacement clutches. The clutch is extremely variable in size averaging around 7–9, with up to 15 or 16 eggs recorded in extreme cases. The clutch size very large relative to related species. Mean clutch sizes were 7.5 in a sample of 24 in Hooper Bay (range of 5–11); 6.7 in a sample of seven from Utqiaġvik (4–9); 9 in a sample of a sample of 5 in Baffin Island; 9.8 on Victoria Island; 8.4 (in a sample of 14) on Elsemere Island; 7.4 on Wrangel Island and 7.74 in Finnish Lapland. The average clutch size was 9.8 in a good year in Victoria Island (Canada), Victoria Island while in a good year in Utqiaġvik the mean was 6.5. The clutch is laid directly to the ground and are pure, glossy white. An average egg is around with a range of heights from and diameter of . Egg weights are around , the median or average being in different datasets. The average egg size is relatively small, about 20% smaller than Eurasian eagle-owl eggs and 8% smaller than great horned owl eggs. Laying intervals are normally 2 days (41–50 hours mostly).Schaanning, H. T. L. (1907). ''Østfinmarkens fuglefauna''. Bergens Mus. Arb. 8:1–98. The laying intervals can range up to 3–5 days in inclement weather. The laying of a clutch of 11 eggs can take 20–30 days, while a more typical nest of around 8 takes about up to 16 days. The interval between the 8th and 9th eggs can be up to about 4 days. Incubation begins with the first egg and is by female alone, while she is fed by her mate.


Parental behavior

Food is brought to the nest by males and surplus food is stored nearby. Females in breeding season often develop a very extensive brood patch which in this species is a fairly enormous, high vascularized featherless area of pink belly skin. Incubation lasts 31.8–33 days (unconfirmed and possibly dubious reports from as little as 27 to as much as 38-day incubations). The female alone broods the young, often while simultaneously incubating still unhatched eggs. Sometimes older chicks incidentally brood their younger siblings and females may shelter the young under her wings during inclement weather. When first feeding the young, the female may dismantle prey to feed the young only the softer body parts then gradually ramping up the size of proportions until they eat a whole prey item. Aggressive encounters with parent snowy owls are said to be "genuinely dangerous" and one resource claimed the snowy owl to be the bird species with the most formidable nest defense displays towards humans. The usual response to sighted humans near the nest is mild but continued approach begins to increasingly irritate the parents. At times, humans are forcefully dive-bombed upon, while other potential threats are dealt with in a “forward-threat” where the male walks towards the intruders, engaging in impressive feather-raising and fanning out of half-spread wings until they run forward and slash with both their feet and bill. Fairly serious injuries have been sustained in the worst of snowy owl defensive attacks, including cranial trauma, requiring researchers to make the long trek back to medical care, although human fatalities are not known. Snowy owl parents have been seen to aggressively attacked glaucous gulls, arctic fox and dogs in breeding ground in Utqiaġvik. Non-predatory animals like Reindeer, caribou in Utqiaġvik and sheep (''Ovis aries'') in Fetlar are attacked as well, possibly to avoid potential trampling of the eggs or the young. Males are said to do the majority of nest defense but the female will also often become involved as well. Analysis showed in Lapland, Sweden, that females in nest defense against people engaged in vocal displays (warning and mewing calls) and that males did not engage in mewing but did engage in most hooting calls, many warning calls and almost all physical attacks. In other instances, distraction displays are engaged in against predators, with a "broken-wing act" including high, thin squeals interspersed with weird squeaks, often taking flight only to quickly fall from the sky and imitate a struggle. One author recorded a male to draw him about from the nest before ceasing. 77% of 45 distraction displays in Lapland, Sweden were by females.


Development of young

Hatching intervals are generally from 1 to 3 days, quite often within 37–45 hours apart. New chicks are Altriciality, semi-altricial (i.e. typically helpless and blind), initially being white and rather wet but dry by the end of the first day. The weight of 7 hatchlings was , with an average of while 3 were . Due to the pronounced asynchrony of the egg-laying and hatching, the size difference between siblings can be enormous and in some cases when the smallest chick weighs only , the biggest chick already has attained a weight of around . When the oldest chick is about 3 weeks, the female will start to hunt as well as the male and both may directly feed the young although in some cases they may not need hunt very much if lemmings are particularly numerous. Hoarding (animal behavior), Caches of lemmings around a nest may include more than 80 lemmings that can support the family. Unlike many owls, the chicks of snowy owls are not known to behave aggressively toward one another or to engage in siblicide, perhaps in part due to the need for energy conservance. Some cases of cannibalism of chicks by the family group were thought to be cases where chicks die from other causes. When they are about 2 weeks, the chicks may begin to walk around the nest site which they leave by 18–28 days, although they are still unable to fly and may find safety in nooks and crannies of vegetation and rocks usually only about from the nest mound, as well as via their parents defense.Romero, L. M., Holt, D. W. Maples M. & Wingfield, J. C.. (2006). ''Corticosterone is not correlated with nest departure in Snowy Owl chicks (Nyctea scandiaca)''. General and Comparative Endocrinology 149 (2): 119–123. Leaving the nest is thought to likely be an anti-predator strategy. The male snowy owl may drop fresh prey deliveries directly on the ground near the wandering young. After about three weeks of age, the young may wander fairly widely, rarely to , but usually stay within of the nest mound. Threat postures by young in reaction to researchers were first noticeable at about 20–25 days of age and common at about 28 days and the chicks can be impressively quick and agile-footed. The first fledgling occurs at around 35–50 days, and by 50–60 days the young can fly well and hunt on their own. The total care period is for 2–3.5 months, increasing in length with increased size of the brood. Although independence was once thought to be sought by late August or early September but is more likely by late September to October when migration season for the species begins. The nesting cycle is similar in length to the Arctic short-eared owls and faster than Eurasian eagle-owls by up to 2 months.Schrezinger, W. (1974). ''Zur Ethologie und Jugendentwicklung der Schnee-Eule Nyctea scandiaca nach Beobachtungen in Gefangenschaft''. J. Orn, 115: 8–49.


Maturity and nesting success

Sexual maturity reached the following year but the first breeding is normally at no sooner than the end of the second year of life. There is little strong evidence of typical age of first breeding but initial breeding by males could be inferred by the plumage of males in Utqiaġvik by plumage. At that stage, which the males were essentially all pure white, most were aged to about 3 to 4 years old. The snowy owl seems to markedly inconsistent in regard to breeding every year, often taking at least up to two years between attempts and sometimes as much as nearly a decade. 7 satellite-marking females in Canada proved that they did breed in consecutive years, with 1 breeding over 3 consecutive years. In 23 years at Utqiaġvik, snowys bred in 13 of them. Nesting success can reach 90–100% in even the largest clutches in high lemming years. While over the course of 21 years, 260 total nests were recorded in Utqiaġvik. There, from 4–54 nests were recorded annually. The Utqiaġvik nests bore 3 to 10 sized-clutches with a mean of 6 eggs per nest and an annual mean hatching success from 39 to 91%. 31–87% of chicks were able to depart on foot and 48–65% were annually estimated to survive to fledge; elsewhere, 40% survived to fledge. In another set, 97% of observed eggs both hatched and fledged. In Norway, the fledging success from 10 nests was much lower at about 46%. Norwegian data, which previously indicated it to be an almost accidental breeder in northern Norway, indicates that it is a more regular breeder than expected, though. 3 good years were found for snowy owls between 1968 and 2005: 1974 (when there were 12 pairs), 1978 (22 pairs) and 1985 (20 pairs), with 14 additional locations when potential (but not confirmed) breeding has occurred. The main determinable causes of nest failure were deemed to be
starvation Starvation is a severe deficiency in caloric energy intake, below the level needed to maintain an organism's life. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, dea ...
and Hypothermia, exposure. A number of Norwegian and Finnish nests were known to fail due to severe black fly parasitism.


Longevity

The snowy owl can live a long life for a bird. Records show that the oldest snowy owls in captivity can live to 25 to even 30 years of age. Typical lifespans probably reach around 10 years in the wild. The longest known lifespan in the wild was of a snowy owl initially banded (possibly in its first winter) in Massachusetts and recovered dead in Montana 23 years and 10 months later. The annual survival rate for twelve females on Bylot Island was estimated at around 85–92.3%. It is often reputed that snowy owls frequently died from starvation, with historical accounts opining that they "had to" leave their breeding grounds due to lemming "crashes" but would starve to the south. However, it was proven fairly early on that snowy owls often do survive throughout the winter. This is reinforced somewhat by small radio-tracking and banding studies of snowy owls in the northern Great Plains and the intermountain valleys of the northwestern United States. More circumstantial evidence shows a lack of starvation in the eastern part of North America as well. There is evidence that some adults are known to return to the same wintering areas in ensuing years, areas which are far south of their breeding range. At Logan Airport, most snowy owls that are seen appear to be in good condition. Of 71 dead snowy owls found in winter in the northern Great Plains, 86% died from assorted Major trauma, traumas, including Roadkill, collisions with automobiles and other, usually manmade, objects as well as electrocutions and Culling, shootings. Only 14% of the 71 deaths were due to apparent starving. Data showed some owls appeared to incur injuries but healed and survived. More evidence was found in wintering snowy owls in New York of Bone healing, healed fractures, though some may require surgery to recover. 537 wintering birds in Saskatchewan were studied based on Fatty acid metabolism, fat reserves, which were superior in females over males and adults over juveniles; while 31% of females lacked fat reserves, at least 45% of males found starving or in a state of infirmity were males and 63% turned into Wildlife rehabilitation centres were also males. In British Columbia, of 177 snowy owl deaths, of owls to die, only a small percentage were due to natural causes, such as assumed starvation at 13% and 12% were "found dead". One fledgling on Fetlar died due to pneumonia and ''Staphylococcus'', while a second died from ''Aspergillosis''. Evidence shows that in Utqiaġvik during exceptionally prolonged rains (i.e. 2 to 3 days), nest-departed young were vulnerable to starvation, leading to hypothermia and pneumonia. Due to their natural history, the snowy owl may be affected more severely by Parasitism, blood parasitism than other raptors, due to lowered Immunity (medical), immunity. Conversely, they appear to have lower levels of ectoparasites such as Mallophaga, chewing lice than other large owls per large samples from
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 ...
. The snowy owls averaged about 3.9 chewing lice per host against 7.5 for great grey owls and 10.5 for great horned owls.


Status

This species presence and numbers is dependent on amount of food available. In "lemming years", snowy owls can appear to be quite abundant in habitat. Numbers of snowy owls are difficult to estimate even within studies that take place over decades due to the nomadic nature of adults. The population of
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, ...
has long been perceived as very small and Ephemerality, ephemeral with Finland holding 0–100 pairs; Norway holding 1–20 pairs and Sweden holding 1–50 pairs. A low breeding population within European Russia has been estimated to hold 1,300–4,500 pairs and Greenland to have 500–1,000 pairs. Other than northern part of the American continent, a majority of the snowy owl's breeding range is in northern Russia, but overall estimates are not known. An exact count of 4,871 individuals were seen on surveys between the Indigirka River, Indigirka and Kolyma rivers. The numbers estimated by Partners in Flight and other authors by the 2000s was that North America held about 72,500 snowy owls, about 30% of which were juveniles. The Canadian population of snowy owls was estimated at 10,000–30,000 (in the 1990s) or even to 50,000–100,000 individuals, perhaps improbably. Within Canada, the population on Banks Island was once claimed at up to 15,000–25,000 in productive years and in Queen Elizabeth Islands at about 932 individuals. Alaska is the only state with breeding snowy owls but has probably quite a bit fewer breeding owls than does Canada. Furthermore, the Partners in Flight and the IUCN estimated that the world population was roughly 200,000–290,000 individuals as recently as the 2000s. However, in the 2010s, it has been discovered that all prior estimates were extremely excessive and that more precise numbers could be estimated with better surveying, Phylogeography, phylogeographic data and more insights into the owl's free-wheeling wanderings. It is now believed that there are only 14,000–28,000 mature breeding pairs of snowy owls in the world. During lemming declines, the number of nesting females may drop down to as low as 1,700 worldwide, a dangerously low number, and the number of snowy owls worldwide is less than 10% of what it was once thought to be. Due to the small and rapidly declining population, the snowy was uplisted in 2017 to being a vulnerable species by the IUCN. A 52% decline has been inferred for the North American population since the 1960s with another even more drastic estimate placing the decline from 1970 to 2014 at 64%. Trends are harder to delineate in Scandinavia but a similar downward trend is thought to be occurring. Snowy owls are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES) meaning international trade (including in parts and derivatives) is regulated.


Anthropogenic mortality and persecution

Of 438 band encounters in the USG banding laboratory, almost all causes of death that could be determined, whether intentional or not, were correlated with human interference. 34.2% or 150 were dead due to unknown causes, 11.9% were shot, 7.1% were hit by automobiles, 5.5% were found dead or injured on highways, 3.9% were collision from towers or wires, 2.7% were in animal traps, 2.1% in airplane birdstrikes, 0.6% were Wire obstacle, entangled while the remaining 33.3% recovered injured due to assorted or unknown causes. Snowy owls are endangered by heavy airport usage resulting in birdstrikes. Many such collisions are known in Canada and likely also in
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 of ...
and Mongolia . Despite their danger to planes, no human fatalities have been recorded in collisions with this species. Snowy owls are always far outnumbered in Canadian airports in winter by
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. However, relative to its scarcity, the snowy accounts for a very large balance of the birdstrikes recorded at American airports due to the attractiveness of the habitat, accounting for 4.6% of 2456 recorded collisions (the barn owl is the most frequently involved in birdstrikes). The species is locally vulnerable to pesticides. The placement of buildings in the Utqiaġvik is now thought to have displaced some snowy owls. In Norway, potential sources of disturbance near the nests include tourism, recreation, Reindeer herding, reindeer husbandry, Traffic, motorized traffic, dogs, photographers, ornithologists and scientists. Some biologist have expressed concern that Telemetry, radio-tagging of snowy owls may cause some unclear detrimental effect on snowy owls but little evidence is known if they actually make the owls more susceptible to death. Snowy owls can be quite wary, as they are not infrequently hunted by Circumpolar peoples. Historically, the snowy owl was one of the most persecuted owl species. In the irruption of 1876–77, an estimated 500 snowy owls were shot, with similar numbers in 1889–90 and an estimated 500–1,000 killed in Ontario alone during 1901–02 invasion and about 800 killed in the 1905–06 invasion. Indigenous people of the Arctic historically killed snowy owls as food but now many communities in northern Alaska are fairly modernized, therefore biologists feel that the permitted killing of snowy owls by the indigenous is outdated. The consumption of snowy owls by humans has been proven as far back as ancient cave deposits in France and elsewhere, and they have even been considered as one of the most frequent food species for early humans. They do not shun developed areas especially with old field that hold rodents and, due to lack of human experience, can be extremely tame and unable to escape armed humans. In British Columbia, of 177 snowy owl deaths, the most often diagnosed cause of death was shootings at 25%, often well after legal protection of the species. The number Poaching, poached snowy owls in Ontario is opined to be unusually high considering their scarcity.Desmarchelier, M., Santamaria-Bouvier, A., Fitzgérald, G., & Lair, S. (2010). ''Mortality and morbidity associated with gunshot in raptorial birds from the province of Quebec: 1986 to 2007''. The Canadian Veterinary Journal, 51(1), 70. While the species was once otherwise killed as food and then later shot out of resentment for perceived threats against domestic and favored game stock, the reasoning behind ongoing shooting of snowy owls into the 21st century is not well-understood. Siberian snowy owls are frequently victim to Bait (luring substance), baited Trapping, fox traps, with possibly up to around 300 killed in a year based upon very rough estimates. Warfarin poisoning in use as rodenticides are known to kill some wintering snowy owls, including up to six at Logan Airport alone. Mercury (element), Mercury concentrations, most likely through bioaccumulation, have been detected in snowy owls in the Aleutian Islands but it is not known whether fatal mercury poisoning has occurred. Polychlorinated biphenyl, PCBs may have killed some snowy owls in concentration. Some airports have advocated and instituted the practice of shooting owls to avoid birdstrikes but successful Species translocation, translocation is possible and preferred given the species protected status. Global warming, Climate change is now widely perceived to perhaps the primary driver of the snowy owl's decline. As temperatures continue to rise, abiotic factors such as increased rain and reduced snow are likely to effect lemming populations and, in turn, snowy owls. These and potentially many other issues (possibly including modifying migrating behavior, vegetation composition, increased insect, disease and parasite activities, risk of hyperthermia) are a matter of concern. Additionally, reduction of sea ice, which snowy owls are now known to rely extensively on, as a result of warming climates, impacts could be significant. The effect of climate change was essentially confirmed in northern Greenland where a perhaps irrevocable collapse of the lemming population was observed. From 1998 to 2000, the lemming numbers appeared to have quickly declined. The number of lemmings per hectare (ha) is less than one-fifth of what it once was in Greenland (i.e. from 12 lemmings per ha to less than 2 per ha at peak). This is almost certainly correlated with a 98% decline in owl productivity as well as that of the local stoats (the long-tailed jaeger and
Arctic fox The Arctic fox (''Vulpes lagopus''), also known as the white fox, polar fox, or snow fox, is a small fox native to the Arctic regions of the Northern Hemisphere and common throughout the Arctic tundra biome. It is well adapted to living in ...
es, though previously thought to be almost as reliant on lemmings, seem to be more loosely coupled and more generalized and did not decline as much). The amount of lemming mounds is much less than it once in northern Greenland and any variety of population cycle has been apparently abandoned by what remains of the lemmings.


In popular culture

* The ''Harry Potter'' books by J. K. Rowling, and subsequent Harry Potter (film series), films of the same name, feature a female snowy owl named Magical creatures in Harry Potter#Hedwig, Hedwig. Concern was expressed by some in the media that the popularity of the Harry Potter films would cause an increase in the Black market, illicit Wildlife trade, owl trade of snowy owls. However, there was no strong evidence of an increase in snowy owls confiscated from the black market, despite a larger than typical number of snowy owls being reported at Wildlife rehabilitation, wildlife centres. * The EADS Harfang, drone aircraft developed by the French Air Force, is named in French for the snowy owl (''Harfang des neiges''). * The snowy owl ( in French) is the avian symbol of Quebec. * "White Owl" is a brand of cigars which features the Snowy Owl in its advertising.


References


External links


Free Video About Snowy Owls

Snowy owl increasingly casting its spell over North American skies
(Jan. 2015), ''The Guardian (UK), The Guardian''
Snowy Owl Species Account
Cornell Lab of Ornithology

USGS Patuxent Bird Identification InfoCenter * * * {{Taxonbar , from=Q170177 Bubo (genus), snowy owl Birds of the Arctic Birds of Scandinavia Holarctic birds Birds of Manchuria Birds described in 1758, snowy owl Provincial symbols of Quebec Taxa named by Carl Linnaeus, snowy owl