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Snowy owl
Temporal range: Pleistocene–Present
Snowy Owl (240866707).jpeg
Conservation status
CITES Appendix II (CITES)
Scientific classification
Genus:
Bubo
Species:
scandiacus
Cypron-Range Bubo scandiacus.svg

     Breeding      Non Breeding
Synonyms
  • Strix scandiaca Linnaeus, 1758
  • Strix nyctea Linnaeus, 1758
  • Nyctea scandiaca (Linnaeus, 1758)

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.

Description

It one of the largest species of owl, and it is the only owl with mainly white plumage. Often when seen in the field, these owls can resemble a pale rock or a lump of snow on the ground.

Males tend to be a purer white overall while females tend to more have more extensive flecks of dark brown. Juvenile male snowy owls have dark markings that may appear similar to females until maturity, but later turn whiter. One can tell the age and sex of a snowy owl by the composiotion of these markings.

Bubo scandiacus (Linnaeus, 1758) Male
A captive adult male.
Snowy Owl - Schnee-Eule
A captive adult female.

The snowy owl has bright yellow eyes. The snowy owl was determined to have eyesight better suited to long-range perception than to close discrimination. Like other owls, snowy owls can probably perceive all colors but cannot perceive ultraviolet visual pigments.

Snowy owl Wings 212
Wing structure

The head is relatively small, the facial disc is shallow and the ear is uncomplicated. 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 than perhaps to increased nocturnality and predatory behavior.

Size

The snowy owl is a very large owl. They are the largest bird predator of the High Arctic 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.

Females are larger than males. This is propbably because the need to be able to withstand food shortages during incubating and brooding. Male snowy owls have been known to measure from 52.5 to 64 cm (20.7 to 25.2 in) in total length. In females, total length has been known to range from 54 to 71 cm (21 to 28 in).

Vocalizations

Perhaps as many as 15 different calls by mature snowy owls have been documented. 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 somewhat reminds 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.

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.

Bubo scandiacus Delta 6
Juvenile owls do not mind associating with one another, especially during winter.

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.

Juvenile male calling for its mother
Juvenile snowy owl, about 12 weeks old

Habitat

Snowy owls are native to the Arctic regions of both North America and the Palearctic, breeding mostly on the tundra.

During the wintering, many snowy owls leave the dark Arctic to migrate to regions further south. 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 Siberia, Sakhalin southern Kamchatka and, rarely, north China and sometimes the Altai Republic. 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 to Labrador.

The earth in snowy owl breeding grounds is covered with mosses, lichens and some rocks. Often the species can be seen in areas with some rising elevation such as hummocks, knolls, ridges, bluffs and rocky outcrops.

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 coastal spots, lakeshores, islands, moorlands, steppes, meadows, prairies, other extensive grasslands and rather shrubby areas of the Subarctic.

Behaviour

Most owls sleep during the day and hunt at night, but the snowy owl is often active during the day, especially in the summertime.

Snowy owls often spend a majority of time on the ground, and perched mostly on in trees or rocks and prefer a flat surface to sit upon. However, they may perch on hummocks, fenceposts, telegraph poles by roads, radio and transmission towers, haystacks, chimneys and the roofs of houses and large buildings when hunting.

Diet

The snowy owl is both a specialized and generalist hunter. The snowy owl can adapt to almost any available prey – most often other small mammals, like lemmimgs, and northerly water birds, as well as, opportunistically, carrion.

Birds may regularly include passerines, northern seabirds, ptarmigan and ducks, among others. Sometimes infrequent consumption of other prey such as beetles, crustaceans and occasionally amphibians and fish is reported.

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.

Breeding

Snowy owls typically nest on a small rise on the ground of the tundra. The snowy owl lays a very large clutch of eggs, often from about 5 to 11, with the laying and hatching of eggs considerably staggered. Despite the short Arctic summer, the development of the young takes a relatively long time and independence is sought in autumn.

The snowy owl is a nomadic bird. They rarely breed at the same locations or with the same mates. They often do not breed at all if prey is unavailable.

Most individuals arrive at the nest site by April or May with a few overwintering arctic exceptions. Males advertises potential nest sites to his mate by scratching the ground and spreading his wings over it. The nest is usually a shallow depression on a windswept eminence in the open tundra.

Tundra Polygons and Pingos (9514080830)
Snowy owls often seek out polygons such as these in the tundra.
Eggs of British Birds Seebohm 1896 Plate6
An illustration of 8 European owl species' eggs, with the snowy owl in the middle of the right row. Note the much larger egg of the Eurasian eagle-owl at bottom.

Egg-laying normally begins during early May to the first 10 days of June. The clutch is extremely variable in size averaging around 7–9, with up to 15 or 16 eggs recorded in extreme cases. The female owl lays eggs one after another. The laying intervals can range up to 3–5 days in inclement weather. Incubation begins with the first egg and is by female alone, while she is fed by her mate.

Longevity

The snowy owl can live a long life for a bird. Records show that the oldest snowy owls in captivity can live to 25 to even 30 years of age. Typical lifespans probably reach around 10 years in the wild. The longest known lifespan in the wild was of a snowy owl initially banded (possibly in its first winter) in Massachusetts and recovered dead in Montana 23 years and 10 months later.

Predators

Largely in winter, snowy owls have been the victim of a number of larger avian predators, though attacks are likely to be singular and rare. Instances of predation on snowy owls are known to have been committed several times in winter only by Eurasian eagle-owls. Additionally, golden eagles (Aquila chrysaetos) have been known to prey on snowy owls as well as all northern sea eagles: the bald (Haliaeetus leucocephalus), white-tailed (Haliaeetus albicilla) and Steller's sea eagles (Haliaeetus pelagicus). Snowy owls are also sometimes killed by birds that are mobbing them. In one instance, a peregrine falcon killed a snowy owl in a stoop after the owl had itself killed a fledgling falcon. Anecdotal report indicate predation by gyrfalcons (on snowy owls of unknown age and condition) but it was possibly also an act of mobbing. In another, a huge throng of Arctic terns (Sterna paradisaea) relentlessly swarmed and attacked a snowy owl until it met its demise.

Status

This species presence and numbers is dependent on amount of food available. In "lemming years", snowy owls can appear to be quite abundant in habitat. Numbers of snowy owls are difficult to estimate even within studies that take place over decades due to the nomadic nature of adults.

However, recent data suggests the species is declining precipitously. 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. The causes are not well understood, but complex environmental factors, like global warming, are probably threatening the snowy owl's existence. Due to the small and rapidly declining population, the snowy was uplisted in 2017 to being a vulnerable species by the IUCN.

Snowy Owl, Gerald R. Ford Int'l Airport, Grand Rapids, MI, 5 December 2013 (11230541096)
Snowy owls often favor airports, such as this one at Gerald R. Ford International Airport, in winter but the risk of birdstrike is high in such areas.

In popular culture

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

See also

Kids robot.svg In Spanish: Bubo scandiacus para niños

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