The snowy owl (''Bubo scandiacus''), also known as the polar owl, the white owl and the Arctic owl, is a large, white owl of the true owl family. Snowy owls are native to the

Arctic 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 lemmings, 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 birds, 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, 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" and ''scandiacus'' is New Latin 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 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 owls 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. 121 Snowy Owl

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 The tarsometatarsus is a bone that is only found in the lower leg of birds and some non-avian dinosaurs. It is formed from the fusion of several bones found in other types of animals, and homologous to the mammalian tarsus (ankle bones) and meta ...

, to outright distinguish the snowy owl from other modern species like the Eurasian eagle-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 (''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 revealed to not be at all closely related. Within the owl order, typical owls are highly divergent from barn-owls. 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 ''Strix'' is a genus of owls in the typical owl family (Strigidae), one of the two generally accepted living families of owls, with the other being the barn-owl (Tytonidae). Common names are earless owls or wood owls, though they are not the onl ...

'', 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 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'' with the h ...

'' 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,

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 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 Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species, it ranges widely from the number of species to differences within species and can be attributed to the span of survival for a species. It is dis ...

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 (''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 The barn owl (''Tyto alba'') is the most widely distributed species of owl in the world and one of the most widespread of all species of birds, being found almost everywhere except for the polar and desert regions, Asia north of the Himalaya ...

(''Tyto alba''), the sexual dimorphism of spotting appears to be driven by genetics while, in snowy owls, environment may be the dictating factor instead. Snowy Owl - Schnee-Eule

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 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, 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, a proportionately greater length to the interorbital roof and a much longer sclerotic ring 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

dioptre A dioptre (British spelling) or diopter (American spelling) is a unit of measurement with dimension of reciprocal length, equivalent to one reciprocal metre, 1 dioptre = 1 m−1. It is normally used to express the optical power of a lens or curv ...

s 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 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 (''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 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, 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 (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'' 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. The bird, its form and function (1906) (14755679525)

The bird, its form and function (1906) (14755679525)

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

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 and the great horned owl 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 habitats normally used by wintering snowy owls are also distinct from the typical edge 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 (''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. Juvenile male calling for its mother

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

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. Bobby Tulloch and snowy owl nest site, Fetlar, Shetland, 1967

Between 1967 and 1975, snowy owls bred on the remote island of Fetlar 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 Robert "Bobby" John Tulloch Member of the Most Excellent Order of the British Empire, MBE (4 January 1929 – 21 May 1996) was a natural history, naturalist from the Shetland Islands, in the north of Scotland. Bobby Tulloch was born on a Croft ...

. 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. Older records show that the snowy owls may have once semi-regularly bred elsewhere in the

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 north ...

) 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

. 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, Yugorsky Peninsula,

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 Eas ...

(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 has ...

) 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 in southern Perm Krai. 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 Isles may refer to: Places *British Isles, often referred to as "the Isles" *Kingdom of the Isles, a medieval realm comprising the Hebrides, the islands of the Firth of Clyde, and the Isle of Man People * Carlin Isles (born 1989), American rugby ...

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,

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,

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

, 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 wildlife ...

to Utqiaġvik, 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, and rarely even south to the Shumagin Islands. The snowy owl may breed extensively in northern Canada, largely making its home in the

Arctic Archipelago The Arctic Archipelago, also known as the Canadian Arctic Archipelago, is an archipelago lying to the north of the Canadian continental mainland, excluding Greenland (an autonomous territory of Denmark). Situated in the northern extremity of No ...

. 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 Cape Sheridan is on the northeastern coast of Ellesmere Island, Canada situated on the Lincoln Sea in the Arctic Ocean, on the mouth of Sheridan River, west bank. It is one of the closest points of land to the geographic North Pole, approx to the ...

, 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), 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 re ...

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). 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, central Russia, southwestern

southern Kamchatka 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, ...

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 polynyas. 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. 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,

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 The Gulf Coast of the United States, also known as the Gulf South, is the coastline along the Southern United States where they meet the Gulf of Mexico. The coastal states that have a shoreline on the Gulf of Mexico are Texas, Louisiana, Mississ ...

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...

Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

, California and even Hawaii. In January 2009, a snowy owl appeared in 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 The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...

area, France,

Crimea Crimea, crh, Къырым, Qırım, grc, Κιμμερία / Ταυρική, translit=Kimmería / Taurikḗ ( ) is a peninsula in Ukraine, on the northern coast of the Black Sea, that has been occupied by Russia since 2014. It has a pop ...

, the

Caspian Caspian can refer to: *The Caspian Sea *The Caspian Depression, surrounding the northern part of the Caspian Sea *The Caspians, the ancient people living near the Caspian Sea *Caspian languages, collection of languages and dialects of Caspian peopl ...

part of Iran, Kazakhstan, northern Pakistan, northwestern India, Korea and Japan. Stragglers may too turn up as far south as the

Azores ) , motto =( en, "Rather die free than subjected in peace") , anthem= ( en, "Anthem of the Azores") , image_map=Locator_map_of_Azores_in_EU.svg , map_alt=Location of the Azores within the European Union , map_caption=Location of the Azores wi ...

and Bermuda.

Habitat

Snowy owls are one of the best known inhabitants of the open Arctic

. Frequently, the earth in snowy owl breeding grounds is covered with

moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...

es,

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

hummock In geology, a hummock is a small knoll or mound above ground.Bates, Robert L. and Julia A. Jackson, ed. (1984). “hummock.” Dictionary of Geological Terms, 3rd Ed. New York: Anchor Books. p. 241. They are typically less than in height and ...

s, knolls,

ridge A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for an extended distance. The sides of the ridge slope away from the narrow top on either side. The line ...

s, bluffs and rocky outcrops. Some of these rises in the tundra are created by

glacial deposits image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...

. The ground is usually rather dry in tundra but in some areas of the southern tundra can also be quite

marsh A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found at ...

y. Not infrequently, they will also use areas of varied

coast The coast, also known as the coastline or seashore, is defined as the area where land meets the ocean, or as a line that forms the boundary between the land and the coastline. The Earth has around of coastline. Coasts are important zones in n ...

al habitat, often

tidal flats Mudflats or mud flats, also known as tidal flats or, in Ireland, slob or slobs, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A global analysis published in 2019 suggested that tidal fl ...

, 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 landscape. Typically wintering sites are rather windswept with meager cover. These open areas can include coastal dunes, other

al spots, lakeshores, islands,

moorland Moorland or moor is a type of habitat found in upland areas in temperate grasslands, savannas, and shrublands and montane grasslands and shrublands biomes, characterised by low-growing vegetation on acidic soils. Moorland, nowadays, generally ...

steppe In physical geography, a steppe () is an ecoregion characterized by grassland plains without trees apart from those near rivers and lakes. Steppe biomes may include: * the montane grasslands and shrublands biome * the temperate grasslands, ...

meadow A meadow ( ) is an open habitat, or field, vegetated by grasses, herbs, and other non-woody plants. Trees or shrubs may sparsely populate meadows, as long as these areas maintain an open character. Meadows may be naturally occurring or artifi ...

s, prairies, other extensive

grassland A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natur ...

s and rather

shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...

by areas of the

Subarctic The subarctic zone is a region in the Northern Hemisphere immediately south of the true Arctic, north of humid continental regions and covering much of Alaska, Canada, Iceland, the north of Scandinavia, Siberia, and the Cairngorms. Generally, ...

. 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 Field may refer to: Expanses of open ground * Field (agriculture), an area of land used for agricultural purposes * Airfield, an aerodrome that lacks the infrastructure of an airport * Battlefield * Lawn, an area of mowed grass * Meadow, a grass ...

s and

rangeland Rangelands are grasslands, shrublands, woodlands, wetlands, and deserts that are grazed by domestic livestock or wild animals. Types of rangelands include tallgrass and shortgrass prairies, desert grasslands and shrublands, woodlands, savannas ...

, as well as large areas of cleared forests. During irruption years when they are found in the northeastern United States, juveniles frequent developed areas including urban areas and

golf course A golf course is the grounds on which the sport of golf is played. It consists of a series of holes, each consisting of a tee box, a fairway, the rough and other hazards, and a green with a cylindrical hole in the ground, known as a "cup". Th ...

s, as well as the expected

s and agricultural areas that older birds primarily use. On the plains of Alberta, observed snowy owls spent 30% of their time in stubble-fields, 30% in

summer fallow Summer fallow, sometimes called fallow cropland, is cropland that is purposely kept out of production during a regular growing season. Resting the ground in this manner allows one crop to be grown using the moisture and nutrients of more than one c ...

, 14% in

hay Hay is grass, legumes, or other herbaceous plants that have been cut and dried to be stored for use as animal fodder, either for large grazing animals raised as livestock, such as cattle, horses, goats, and sheep, or for smaller domesticated ...

field and the remainder of the time in

pasture Pasture (from the Latin ''pastus'', past participle of ''pascere'', "to feed") is land used for grazing. Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, cattle, sheep, or swine ...

, natural grasslands and

slough Slough () is a town and unparished area in the unitary authority of the same name in Berkshire, England, bordering west London. It lies in the Thames Valley, west of central London and north-east of Reading, at the intersection of the M4 ...

s. 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

pests PESTS was an anonymous American activist group formed in 1986 to critique racism, tokenism, and exclusion in the art world. PESTS produced newsletters, posters, and other print material highlighting examples of discrimination in gallery represent ...

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 General Edward Lawrence Logan International Airport , also known as Boston Logan International Airport and commonly as Boston Logan, Logan Airport or simply Logan, is an international airport that is located mostly in East Boston and partially ...

Massachusetts Massachusetts (Massachusett language, Massachusett: ''Muhsachuweesut assachusett writing systems, məhswatʃəwiːsət'' English: , ), officially the Commonwealth of Massachusetts, is the most populous U.S. state, state in the New England ...

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 Bering Sea (, ; rus, Бе́рингово мо́ре, r=Béringovo móre) is a marginal sea of the Northern Pacific Ocean. It forms, along with the Bering Strait, the divide between the two largest landmasses on Earth: Eurasia and The Ameri ...

, the Atlantic Ocean and even the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lakes ...

, 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, 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 Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

, 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 lemmings, and like them, the snowy owl may be considered cathermal. This species can withstand extremely cold temperatures, having been recorded in temperatures as low as minus 62.5

degrees Celsius The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The ...

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 Conduction is the process by which heat is transferred from the hotter end to the colder end of an object. The ability of the object to conduct heat is known as its ''thermal conductivity'', and is denoted . Heat spontaneously flows along a tem ...

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, 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

s, fenceposts,

telegraph pole A utility pole is a column or post typically made out of wood used to support overhead power lines and various other public utilities, such as electrical cable, fiber optic cable, and related equipment such as transformers and street lights. It c ...

s by roads,

radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmit ...

and transmission towers,

stacks,

chimney A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typic ...

s 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

preen Preen may refer to: Birds *Preening, personal grooming of a bird's feathers especially by using its beak *Preen gland, also called the uropygial gland, an oil gland found in many bird species *Preen oil, an oil made by the uropygial gland found ...

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. A Snowy Owl in Flight David Hemmings

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 Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...

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 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 Churchill is a town in northern Manitoba, Canada, on the west shore of Hudson Bay, roughly from the Manitoba–Nunavut border. It is most famous for the many polar bears that move toward the shore from inland in the autumn, leading to the nickname ...

, 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 Horicon Marsh is a marsh located in northern Dodge and southern Fond du Lac counties of Wisconsin. It is the site of both a national and a state wildlife refuge. The silted-up glacial lake is the largest freshwater cattail marsh in the United Sta ...

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 . Bubo scandiacus Delta 4

Migration

It is fair to say that the snowy owl is a partial, if fairly irregular, 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

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

was more concentrated. Some variety of movements recorded each autumn and snowy owls winter annually in plains of

and Mongolia and prairies and

lands of Canada. The

Great Plains The Great Plains (french: Grandes Plaines), sometimes simply "the Plains", is a broad expanse of flatland in North America. It is located west of the Mississippi River and east of the Rocky Mountains, much of it covered in prairie, steppe, an ...

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 , settlement_type = City , nicknames = Twin Ports (with Superior), Zenith City , motto = , image_skyline = , image_caption = Clockwise from top: urban Duluth skyline; Minnesota ...

from 1974 to 2012 would occur in larger numbers in years where

rats Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include ''Neotoma'' (pack rats), ''Bandicota'' (bandicoot ...

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 Cambridge Bay (Inuinnaqtun: ''Iqaluktuuttiaq'' Inuktitut: ᐃᖃᓗᒃᑑᑦᑎᐊᖅ; 2021 population 1,760; population centre 1,403) is a hamlet located on Victoria Island in the Kitikmeot Region of Nunavut, Canada. It is the largest settl ...

were recovered in drastically different spots at least a year later: one in eastern

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

, one in

and one in

Sakhalin Island 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: ...

. A nestling banded in

Hordaland Hordaland () was a county in Norway, bordering Sogn og Fjordane, Buskerud, Telemark, and Rogaland counties. Hordaland was the third largest county, after Akershus and Oslo, by population. The county government was the Hordaland County Municipal ...

was recovered to the northeast in

Finnmark Finnmark (; se, Finnmárku ; fkv, Finmarku; fi, Ruija ; russian: Финнмарк) was a county in the northern part of Norway, and it is scheduled to become a county again in 2024. On 1 January 2020, Finnmark was merged with the neighbouri ...

. In the

Logan Airport General Edward Lawrence Logan International Airport , also known as Boston Logan International Airport and commonly as Boston Logan, Logan Airport or simply Logan, is an international airport that is located mostly in East Boston and partially ...

, 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 Victoria Island ( ikt, Kitlineq, italic=yes) is a large island in the Arctic Archipelago that straddles the boundary between Nunavut and the Northwest Territories of Canada. It is the List of islands by area, eighth-largest island in the world, ...

, 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 The border between Canada and the United States is the longest international border in the world. The terrestrial boundary (including boundaries in the Great Lakes, Atlantic, and Pacific coasts) is long. The land border has two sections: Can ...

, 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

irruption Animal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of migration in ecology. It is found in all major animal groups, including birds, mammals, fish, reptiles, ...

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 summer solstice, also called the estival solstice or midsummer, occurs when one of Earth's poles has its maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere ( Northern and Southern). For that hemisphere, the summer ...

, the owls appear to hunt during "theoretical nightfall".

Night-vision device A night-vision device (NVD), also known as a night optical/observation device (NOD), night-vision goggle (NVG), is an optoelectronic device that allows visualization of images in low levels of light, improving the user's night vision. The devi ...

s 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 The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

breast The breast is one of two prominences located on the upper ventral region of a primate's torso. Both females and males develop breasts from the same embryological tissues. In females, it serves as the mammary gland, which produces and secret ...

, 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. 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 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 hovering flight before dropping onto prey. When hunting fish, apparently, some snowy owls will hover in a style reminiscent of the

osprey The osprey (''Pandion haliaetus''), , also called sea hawk, river hawk, and fish hawk, is a diurnal, fish-eating bird of prey with a cosmopolitan range. It is a large raptor reaching more than in length and across the wings. It is brown o ...

(''Pandion haliaetus''), 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 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 night-migrating

passerine A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped'), which includes more than half of all bird species. Sometimes known as perching birds, passerines are distinguished from other orders of birds by t ...

s and

shorebird 245px, A flock of Dunlins and Red knots">Red_knot.html" ;"title="Dunlins and Red knot">Dunlins and Red knots Waders or shorebirds are birds of the order Charadriiformes commonly found wikt:wade#Etymology 1, wading along shorelines and mudflat ...

s, sometimes perhaps on the wing, as well as large and/or 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 kleptoparasitize the prey caught by the other birds. Few variations of hunting technique were observed in winter observations from

, 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 Syracuse ( ) is a City (New York), city in and the county seat of Onondaga County, New York, Onondaga County, New York, United States. It is the fifth-most populous city in the state of New York following New York City, Buffalo, New York, Buffa ...

, 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

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 fat reserves. These owls were found to have extremely thick 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 duck hunters,

birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

maimed by

antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...

wires, various animals caught in human traps and traplines as well as

domestic Domestic may refer to: In the home * Anything relating to the human home or family ** A domestic animal, one that has undergone domestication ** A domestic appliance, or home appliance ** A domestic partnership ** Domestic science, sometimes cal ...

or wild prey being bred or farmed by humans in enclosures. A wide variety of accrued reports show that the snowy owl that scavenging on

is not uncommon (despite having once been thought to be very rare in all owls), including instances of

reindeer Reindeer (in North American English, known as caribou if wild and ''reindeer'' if domesticated) are deer in the genus ''Rangifer''. For the last few decades, reindeer were assigned to one species, ''Rangifer tarandus'', with about 10 subspe ...

(''Rangifer tarandus'') body parts brought to nests and owls following

s to secondarily feed on their kills. Even huge

marine mammal Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They are an informal group, unified only by their reli ...

s such as walrus (''Odobenus rosmarus'') and whales can be fed upon by these owls when the opportunity occurs. Snowy owls produce a 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

s. Most especially, they often live off of the northerly lemmings. Sometimes other similar rodents like

vole Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of low-c ...

s can also be found frequently in the snowy owl's foods. It is

R-selected In ecology, ''r''/''K'' selection theory relates to the selection of combinations of traits in an organism that trade off between quantity and quality of offspring. The focus on either an increased quantity of offspring at the expense of individ ...

, 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

s, northern

s, ptarmigan and ducks, among others. Sometimes infrequent consumption of other prey such as

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s and occasionally

amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...

s and 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), prey selection tends toward quite small prey, usually small

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

biome A biome () is a biogeographical unit consisting of a biological community that has formed in response to the physical environment in which they are found and a shared regional climate. Biomes may span more than one continent. Biome is a broader ...

s of

and Canada, mean prey sizes for snowy owls were , in western North America, the mean prey size was and in

eastern North America The Nearctic realm is one of the eight biogeographic realms constituting the Earth's land surface. The Nearctic realm covers most of North America, including Greenland, Central Florida, and the highlands of Mexico. The parts of North America ...

was , while the mean prey size in northern

Fennoscandia __NOTOC__ Fennoscandia (Finnish language, Finnish, Swedish language, Swedish and no, Fennoskandia, nocat=1; russian: Фенноскандия, Fennoskandiya) or the Fennoscandian Peninsula is the geographical peninsula in Europe, which includes ...

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 lemmings. 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 Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...

of the ecosystem. Lemmings are key architects of the soil, microtopography and plant life of the entire tundra. In the American lower Arctic areas,

brown lemming The West Siberian lemming or Western Siberian brown lemming (''Lemmus sibiricus'') is a true lemming species found in the Russian Federation. Like other lemmings, it belongs to the Cricetidae family of rodents. It is endemic to Russia, where ...

of the ''Lemmus'' genus are predominant and tend to be found in lower, wetter habitats (feeding by preference on grasses sedges and

es) 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 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

s 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

, among 2,700 prey items only a third were Norway lemmings (''Lemmus lemmus'') and a majority were

s 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 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

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

s, 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,

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 birds 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

, the diet among 139 prey items was 100% avian. The predominant prey were water birds, 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

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

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

, 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 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''),

s, brown bears (''Ursus arctos''), wolverines (''Gulo gulo'') and perhaps especially the Arctic fox.