Snowy owl

Name and taxonomy

Carl Linnaeus described the snowy owl in 1758 in the tenth edition of Systema Naturae, as Strix scandiaca. He took the white males and the barred females for two species and gave the females a second name, Strix nyctea. Bubo is Latin for a horned owl, and scandiacus means of Scandinavia. The old genus name Nyctea comes from the Greek for night.

For most of the 20th century the bird stood alone in its own genus as Nyctea scandiaca. DNA studies then showed it sits close to the horned owls and eagle-owls, so most authorities moved it into Bubo. Some still keep Nyctea, because the leg bones differ from those of the other Bubo owls. The species belongs to the family Strigidae, the true owls, in the order Strigiformes. It is the Schneeeule in German, the harfang des neiges in French and the tunturipollo in Finnish.

Evolution and relatives

Genetic tests put the snowy owl about 8% apart from the other Bubo owls. Its closest living relative is the great horned owl of the Americas, and it split from its relatives about 4 million years ago. In 2013 a German falconer crossed a male snowy owl with a female Eurasian eagle-owl. The young had the ear tufts, orange eyes and markings of the mother and the white base colour of the father.

Fossils show the snowy owl ranged much farther south during the ice ages. Bones have been found in Austria, England, France, Germany, Hungary, Italy, Poland and Spain, and in Illinois. Ice age birds from France were a little bulkier than the modern form and showed a bigger size gap between the sexes. No subspecies are recognised, because the birds wander so widely that populations mix freely.

Appearance

A male measures 52.5 to 64 centimetres long with a wingspan of 116 to 165.6 cm. A female measures 54 to 71 cm and spans 146 to 183 cm. Males weigh 1.3 to 2.5 kilograms and females 1.33 to 2.95 kg. The tail is 18.8 to 28.8 cm long. As in most birds of prey, the female is the larger bird. It is the heaviest and longest-winged owl in North America.

The plumage is whiter than that of a polar bear or an Arctic fox, and a resting owl can pass for a lump of snow. A mature male is plain white above with a few dark spots, and his underside is often pure white. A female carries dark brown spots and bars on the crown, the flanks and the upper breast. Bars mark a female's wing and spots mark a male's, which is the most reliable way to sex a bird. The eyes are bright yellow, the bill is black and the tiny ear tufts are almost never seen.

Chicks hatch greyish white and soon turn dark grey-brown, which hides them among the lichens of the tundra. A young bird looks like a dark female and grows whiter with each moult, reaching adult plumage at three to four years. Some males may not reach their whitest until their ninth or tenth year. The toes carry the longest feathers of any owl, about 33.3 millimetres on average, and the claws are black.

Habitat and range

The snowy owl breeds around the top of the world, mostly north of 60 degrees. The core of the range is northern Alaska, the Canadian Arctic islands and the tundra of northern Russia. It also breeds in northern Greenland, on Spitsbergen and, in some years, in the mountains of Norway. The whole breeding range covers a little over 12,000,000 square kilometres, but only about 1,300,000 of those are used often. Between 1967 and 1975 a pair even bred on Fetlar in the Shetland Islands.

The nesting ground is open tundra of moss, lichen and rock, usually below 300 metres. The owls pick spots with a small rise, a hummock, ridge or knoll, that gives a view over the flat ground. In winter they take almost any open landscape: coastal dunes, prairie, moorland, stubble fields and airports. Logan Airport in Boston holds one of the most reliable winter populations in the United States. Many also winter out on the sea ice and hunt seabirds at open leads.

Winter movements are hard to predict. Southern Canada, the northern United States, Scandinavia, central Russia and northern China see the bird most years. In an irruption year, thousands push far south, and owls have reached Texas, Florida, Hawaii, Bermuda, Iran, Pakistan and Japan. GBIF holds records from 44 countries, many of them from such wanderers.

Diet and hunting

The snowy owl is a hunter of small mammals first and a hunter of birds second. On the tundra, lemmings are the main food, and at Utqiagvik in Alaska they made up almost all of 42,177 prey items over 25 years. An owl may eat about 326 grams of lemmings a day, and one bird can take more than 1,600 in a year. Where lemmings are scarce the owl turns to voles, ptarmigan, ducks, geese, seabirds and shorebirds. More than 200 kinds of prey are recorded, from a shrew of 8.1 g to a red fox of about 6 kg.

Winter diets are broader. Inland owls take voles, mice, rats and rabbits, and coastal owls take ducks, grebes and gulls, often snatched from the water. The snowy owl also eats carrion and has fed on reindeer, walrus and whale carcasses and followed polar bears to their kills. It swallows small prey whole and coughs up the bones and fur as a pellet 18 to 24 hours later.

It hunts mostly by sight from a low rise or a post, sitting still for long spells like a buzzard. Tests show it can spot prey 1.6 kilometres away. The usual attack is a short dash from the perch that ends in a hard pounce. It can hover in a strong wind, plunge through 20 cm of snow for a vole, or chase birds on the wing. It also steals kills from other raptors and takes prey caught in traps.

Behaviour and social life

The snowy owl is active at any hour, though it rests most at noon and midnight. In the Arctic summer it hunts in the twilight around midnight, and in winter it hunts through the short day and the long night. It spends most of its time on the ground or a low rise, because its short broad legs are poorly suited to perching in trees. It walks and runs well and may hold its wings out for balance.

Outside the breeding season the owl lives alone. In winter a female may hold a territory for up to 80 days, while a male stays only a day or two in one place. Loose gatherings of 20 to 30 birds form where food is concentrated, and 31 to 35 once wintered in 2.6 square kilometres in Montana. Nesting pairs space themselves 1.6 to 3.2 km apart at Utqiagvik and do not tolerate close neighbours. Fights are rare but can end with two owls locked by the talons in the air.

The bird stands extreme cold. It has been recorded at minus 62.5 degrees Celsius without distress, and its plumage insulates almost as well as that of an Adelie penguin. On a sunny day it faces its whitest feathers toward the sun about 44% of the time, perhaps as a signal or for warmth. Fat reserves 19 to 22 mm thick let some owls fast for about 40 days.

Communication and senses

The snowy owl's song is a series of two to six rough barks, krooh krooh krooh, closer to a dog than to a hoot. As many as 15 different calls have been recorded. In the thin Arctic air the call carries more than 3 kilometres and perhaps as far as 10 or 11. The male sings to hold his ground and to draw a female, and she answers with a higher, more guttural version. The alarm call is a loud grating keeea, and a rattling rick rick rick or kre kre kre warns of a threat near the nest.

Both sexes clap the bill, or perhaps click the tongue, when annoyed. A threatened owl lowers its front, stretches its head forward, raises its back and spreads its wings. If pressed it rolls onto its back and slashes with its talons. The bird relies on sight more than most owls, because its ears and facial disc are simpler than those of its relatives. Its eyes suit long-range vision over the tundra rather than close work, and it probably sees less well at night than other owls.

Reproduction and life cycle

Most pairs form on the breeding ground in late April or May, and the bond seldom lasts beyond one season. Of 239 breeding attempts at Utqiagvik, 232 were monogamous and 7 involved a male with two females. The male courts with a bouncing, moth-like flight, often with a lemming in his bill, and then bows on the ground with his tail cocked. A female may refuse to breed if he skips the display.

The nest is a bare scrape on a dry, windswept rise with a view over the tundra. The female digs it with her claws over about three days, turning to shape a round bowl, and adds no lining. Laying starts in early May or the first days of June, and the eggs come about every two days. A clutch averages 7 to 9 white eggs, and clutches of 15 or 16 have been recorded in years of plenty. Each egg is about 56.4 by 44.7 millimetres and weighs 47.5 to 68 grams.

The female alone incubates, from the first egg, for 31.8 to 33 days, and the male brings her food. The chicks hatch one to three days apart, so the oldest may weigh 350 g when the youngest hatches at 46 g. The young leave the nest on foot at 18 to 28 days and hide in the rocks and plants nearby. They fly at 35 to 50 days and hunt for themselves by 50 to 60 days, but the parents feed them into September or October. In a good lemming year 90 to 100% of the nests succeed, and a pair may skip breeding for years when food is short. A wild bird typically lives about 10 years, and one captive owl reached 28.

Predators and threats

On the tundra an adult snowy owl has almost nothing to fear. Arctic foxes, wolves, wolverines, bears, jaegers, gulls, ravens and falcons all take eggs and chicks. Parents defend the nest hard and dive-bomb foxes, dogs, gulls and people, and researchers have suffered head wounds. A parent also feigns a broken wing and has drawn an observer 2 km from the nest.

In the south the owl meets larger enemies, and Eurasian eagle-owls and golden, bald and sea eagles have killed adults. Far more often the snowy owl is the killer, and it has taken foxes, cats, mink, hawks, falcons and other owls.

People cause most recorded deaths. Of 438 ringed owls recovered in the United States, 11.9% were shot and 7.1% hit by cars. In British Columbia, shooting was the commonest known cause of death at 25%, long after the bird gained legal protection. Rat poison, mercury, fox traps in Siberia and collisions at airports add to the toll. The deepest threat is a warming Arctic, which brings rain and thin snow that break the lemming cycle the owl depends on.

Population and conservation

The IUCN lists the snowy owl as Vulnerable. For decades the world population was put at 200,000 to 290,000 birds. Better surveys in the 2010s showed those figures were far too high. The best current estimate is 14,000 to 28,000 mature breeding pairs, and in a lemming crash the number of nesting females may fall to 1,700. The IUCN raised the species to Vulnerable in 2017 on the strength of that decline.

North America has lost about 52% of its snowy owls since the 1960s, and one estimate puts the fall from 1970 to 2014 at 64%. Europe holds only a few hundred pairs at most, and Norway, Finland and Sweden all list the bird as Critically Endangered. No nest has been seen in Sweden since 2015, and in 2025 the Swedish Species Information Centre proposed listing it as extinct there. In northern Greenland the lemmings collapsed after 1998, and owl productivity fell by 98%.

The species is on Appendix II of CITES, which regulates trade across borders. The United States protects it under the Migratory Bird Act, and airports now move owls rather than shoot them. iNaturalist holds 12,582 observations, most of them from winter birds in southern Canada and the northern United States.

Relationship with humans

People have eaten snowy owls since the Stone Age, and cave deposits in France hold their bones. Arctic peoples still hunt the bird for food in places, and biologists argue that this right no longer fits modern communities. In the irruption of 1876 to 1877 about 500 owls were shot, and 500 to 1,000 died in Ontario alone in 1901 to 1902. Farmers and gamekeepers shot the owl for taking poultry and game, and some shooting goes on today for no clear reason.

Winter owls draw crowds of birdwatchers and photographers, and irruption years make the news. Trappers in the north lose animals to owls that learn to follow a trapline. At airports the bird is both a risk to aircraft and a regular guest, so staff catch and move the owls elsewhere. A nesting owl will attack a person who comes too close, but no human death is known.

In culture and myth

An Inuit and Yupik story tells how Owl and Raven decorated each other's feathers. Owl gave Raven a coat of soot, and Raven turned Owl white with powder. Many Native American traditions are thought to link owls with death or shape-shifting, while Arctic peoples see wisdom and protection. In northern art the white owl stands for winter and mystery.

The snowy owl is the bird emblem of Quebec, where it is the harfang des neiges. Hedwig, the pet owl in J. K. Rowling's Harry Potter books and films, is a female snowy owl. Some feared the films would fuel an illegal trade in the species, but no clear rise in seized owls followed. Wildlife centres did report more snowy owls than usual in those years.