Snowy owl

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 live in the Arctic regions of North America and the Palearctic, and they mostly nest on the tundra. The name Arctic owl is also used for a racehorse, see Arctic Owl (horse).

The snowy owl has several special features that suit its cold home and way of life, and many of them are different from other owls living today. It is one of the largest owl species and the only owl with mostly white feathers. Males are usually a purer white, while females often have more dark brown flecks. Young male snowy owls have dark markings and can look like females until they grow up, when they usually become whiter. The pattern of brown markings on the wing is the most reliable way to tell the age and sex of a snowy owl, although it is not perfect.

Most owls sleep during the day and hunt at night, but the snowy owl is often active during the day, especially in summer. It is both a specialized and a general hunter. Its breeding and overall numbers depend closely on the amount of lemmings living on the tundra. When lemmings are scarce, and at other times of year, the snowy owl can eat almost any prey it finds. This is most often other small mammals and northern water birds, and sometimes it also eats carrion.

Snowy owls usually nest on a small rise on the ground of the tundra. A female lays a very large group of eggs, often between 5 and 11, and the eggs are laid and hatched at different times. Even though the Arctic summer is short, the young take a fairly long time to grow, and they become independent in autumn.

The snowy owl is a nomadic bird. It rarely returns to the same place or the same mate each year, and it often does not breed at all if there is not enough food. It is largely a migratory bird and can travel almost anywhere close to the Arctic. Sometimes it unpredictably irrupts south in large numbers. Because this owl is so hard to count, little detailed information about its numbers was available in the past. Recent information, however, suggests that the species is declining quickly. The global population was once estimated at over 200,000 birds, but data from the 2010s to 2020s suggests there are probably fewer than 100,000 today, and that the number of successful breeding pairs is about 28,000 or even lower. The causes are not fully understood, but many complex environmental factors, often linked to global warming, are probably a major reason the snowy owl is so vulnerable.

Taxonomy

The snowy owl was one of many bird species originally described by Carl Linnaeus in his famous 1758 10th edition of Systema Naturae, where it was named Strix scandiaca. The genus name Bubo is Latin for "horned owl," and scandiacus is Neo-Latin for "of Scandinavia." The older genus name Nyctea comes from Greek and means "night." Linnaeus first described the different plumages of this owl as separate species. For a time, the snowy owl was placed in its own genus as Nyctea scandiaca. However, mtDNA cytochrome b sequence data shows it is very closely related to the horned owls in the genus Bubo, so it is often grouped with them. Some experts still prefer Nyctea, often because of osteological distinctions, which are differences in bone structure.

Genetic tests show the snowy owl is about 8% genetically different from other Bubo owls, but it shares a fairly recent origin with them. Apart from the bone structure of the tarsometatarsus, a leg bone, little clearly sets it apart from other modern owls such as the Eurasian eagle-owl (Bubo bubo). Genetic testing suggests the snowy owl may have split from related species around 4 million years ago, and its closest living relative is the great horned owl (Bubo virginianus). Owls as a whole form a very distinct group. Birds that look similar, such as those in Caprimulgiformes, are not closely related to them. Within owls, typical owls are very different from barn-owls. The Bubo owls likely grouped with other large owls such as Strix, Pulsatrix and Ciccaba, based on similar voices, hooting behaviour, and the number and structure of their chromosomes and autosomes. Fossils show that snowy owls once lived much farther south during the Quaternary glaciation, when much of the Northern Hemisphere was in an ice age. Their fossil remains have been found in places such as Czechoslovakia, Cape Prince of Wales, Little Kiska Island, St. Lawrence Island, Illinois, and, in the Late Pleistocene, at Kozarnika Cave in Bulgaria. Today, snowy owls show no known differences between groups in different areas, and they readily breed together because they wander widely. Their size differences are likely caused by the environment rather than by genetics, and tests found no clear phylogeographic variation. They also have a similar level of genetic diversity to other European owls. Snowy owls do not normally breed with other owl species in the wild. However, a hobby falconer in Kollnburg, Germany, bred hybrids from a male snowy owl and a female Eurasian eagle-owl in 2013. The two male hybrids had the ear-tufts, size, orange eyes, and markings of their mother, while keeping the black-and-white colours of their father. As of 2014, they had grown up and were healthy.

Description

The snowy owl is mostly white, and it is purer white than predatory mammals such as polar bears and Arctic fox. In the field, it can look like a pale rock or a lump of snow on the ground. Females are usually more spotted and darker than males, and the young birds start out grayish white and then turn dark gray-brown. This coloring camouflages them well against the lichens on the tundra. The snowy owl has bright yellow eyes, and its toes are covered in very long white feathers, the longest known of any owl. It is one of the large owl species and the largest avian predator of the High Arctic. Females are larger than males, which is common among birds of prey. Its flight is steady and direct, and it can hover while hunting. Its calls are a barking sound, and they may carry more than 3 km (1.9 mi). The only other owl that breeds in the High Arctic is the short-eared owl, which is smaller and more tan in color.

Distribution and habitat

The snowy owl is usually found in the northern circumpolar region, where it spends the summer north of latitude 60° north, sometimes down to 55 degrees north. It is a very nomadic bird, and when the numbers of its prey go up and down, it may move to new places, so it has sometimes bred farther south. Its total breeding range is over 12,000,000 km² (4,600,000 sq mi), but only about 1,300,000 km² (500,000 sq mi) have a high chance of breeding, meaning the owls breed at least every 3 to 9 years. Snowy owls nest on the Arctic tundra of the far north of Alaska, northern Canada and the Euro-Siberian region.

From 1967 to 1975, snowy owls bred on the remote island of Fetlar in the Shetland Isles, north of mainland Scotland, where the Shetland RSPB warden, Bobby Tulloch, watched them. In the British Isles they are now rare winter visitors to Shetland, the Outer Hebrides and the Cairngorms. Some have been found as far south as Lincolnshire. They live in northern Greenland and, rarely, Iceland. They also breed across northern Eurasia, including Spitsbergen, western and northern Scandinavia, Finnmark, Hardangervidda and the Scandinavian Mountains. In Russia they live in much of the north, including Anadyr, Koryakland, the Taymyr Peninsula, the Yugorsky Peninsula, the Chukochya River, Sakhalin, the Komi Republic, the Kama River in Perm Krai, the Kola Peninsula, Arkhangelsk Oblast and the Pay-Khoy Ridge. They also live on many Arctic isles of Russia, such as Novaya Zemlya, Severnaya Zemlya, the New Siberian Islands, Wrangel Island, the Commander and Hall Islands. In North America, they nest on the Aleutian Islands, including Buldir and Attu, and across much of northern Alaska, most often from the Arctic National Wildlife Refuge to Utqiaġvik, and more rarely along the western coast, through Nome, Hooper Bay and the Yukon Delta National Wildlife Refuge. In Canada, they may breed across the Arctic Archipelago, from Ellesmere Island to Cape Sheridan, along northern Labrador, around the northern Hudson Bay, throughout Nunavut (especially the Kivalliq Region), northeastern Manitoba, most of northern Northwest Territories (including the delta of the Mackenzie River) and northern Yukon Territory, where they breed mostly on Herschel Island.

During winter, many snowy owls leave the dark Arctic to fly to places farther south, though it is hard to say exactly where the southern edge of their winter range is. Some owls stay in the Arctic all winter, but they rarely return to the same places they bred. Because it is difficult and dangerous for scientists to study them in the harsh winter, little is known about how many owls spend winter in the tundra. Their winter range has at times included Iceland, Ireland, Scotland, the Baltics, central Russia, southwestern Siberia, southern Kamchatka, and sometimes the Altai Republic. In North America, they regularly spend winter across much of southern Canada, from British Columbia to Labrador, and they sometimes winter in the Aleutian islands. Since at least the 1970s, research has shown that they also spend winter in several northern seas, perching on sea ice and hunting mostly seabirds in polynyas. In February 1886, a snowy owl landed on a steamship near the Grand Banks of Newfoundland, more than 800 km from land. In some winters, large numbers of snowy owls travel much farther south than usual, called irruptions, which are thought to happen after good breeding years. They have been seen as far south as Georgia, Kentucky, South Carolina, most of the Gulf Coast of the United States, Colorado, Nevada, Texas, Utah, California and even Hawaii. In January 2009, an owl appeared in Spring Hill, Tennessee, the first sighting there since 1987. Snowy owls live in open Arctic tundra, where the ground is often covered with mosses, lichens and rocks. They often prefer raised areas such as hummocks, knolls, ridges, bluffs and rocky outcrops, and many of these rises are made by glacial deposits. In winter they often use windy, open places such as coastal dunes, lakeshores, moorlands, steppes, meadows, prairies and farm fields. Airports are among the most consistently used places in North America, since they are flat, grassy and have many pests and other animals to eat. Over water, they often sit on ice floes in the Bering Sea, the Atlantic Ocean and even the Great Lakes.

Behavior

Snowy owls can be active during the day or at night. In the far north's winter, they have been seen active even during the very short daylight. In summer, they often peak in activity during twilight, the darkest time available. In Norway, the peak time is reportedly between 9:00 pm and 3:00 am. Owls that once nested on Fetlar were most active between 10:00 and 11:00 pm. As days get longer near autumn in Utqiaġvik, owls become more active around nightfall and can often be seen resting during the day, especially in the rain. Their activity likely follows their main food, lemmings, and like them, the snowy owl may be considered cathemeral. Snowy owls can withstand extremely cold temperatures. They have been recorded in temperatures as low as minus 62.5 degrees Celsius with no obvious discomfort. Their feathers hold in heat so well that, on average, only the Adelie penguin has a lower thermal conduction to its plumage. They rival the best insulated animals, such as Dall sheep and the Arctic fox. They spend much of their time on the ground, often on a slight rise, because their short, broad legs make perching in trees or on rocks difficult. In winter, they perch more often on hummocks, fenceposts, telegraph poles, radio and transmission towers, haystacks, chimneys, and rooftops, mainly when hunting. They walk and run quickly and fly with fairly rowing wingbeats broken up by gliding. They can swim but rarely do.

Snowy owls fight now and then, and fights are rarer in winter. During threat displays, an owl lowers the front of its body, stretches its head forward, and raises its back. In winter in Calgary, Alberta, females are territorial and may stay in one area for up to 80 days, while males usually stay only 1–2 days. Owls often gather in aggregations, especially nearer the Arctic. Nests can be fairly close together at Churchill, Manitoba and Southampton Island. The first known study of winter territories took place at Horicon Marsh. The snowy owl is a partial, fairly irregular migrant with a broad but patchy wintering range. A study of owls in the Kola Peninsula found they arrived around 10 November and left around 13 April, clustering where prey was concentrated. Owls winter in Siberia, on prairies and marshlands, and in the Great Plains, and wintering numbers in Duluth, Minnesota rise in years when rats are plentiful. Owls banded in Cambridge Bay have been found as far apart as Ontario, Hudson Bay, and Sakhalin Island. A nestling banded in Hordaland was recovered in Finnmark. Some owls banded at Utqiaġvik traveled to Victoria Island and Banks Island, and one reached the Canada–United States border before wintering in the same border areas. Records also include owls at Logan Airport and near the Gulf of Alaska. Large numbers have appeared in Canada and the United States in many winters, called irruption years.

Diet and hunting

Snowy owls may hunt at almost any time of day or night, but they may not hunt during very bad weather. Scientists using night-vision devices have seen that snowy owls often hunt during the long nights of the northern winter. Snowy owls often swallow small prey whole. Their stomachs digest the meat, and the parts they cannot digest, such as bones, teeth, fur, and feathers, are pressed into oval pellets that the bird later coughs up. Scientists study these pellets to learn what the owls have eaten. Snowy owls mostly find prey by sight and movement. They often wait on a raised spot, then swoop down on their prey. They also hunt by chasing prey in flight, and in winter they can dive into the snow to catch prey hiding beneath it.

The snowy owl mainly hunts mammals, especially collared lemmings, which are small rodents of the tundra. They also eat birds such as ducks and seabirds, and sometimes beetles, fish, and other small animals. More than 200 prey species have been known to be eaten by snowy owls around the world. They also eat carrion, including reindeer remains, and sometimes follow polar bears to feed on their kills. Their diet changes with the seasons and places. In winter, they eat more mice, voles, and water birds.

Breeding

Most snowy owls have one mate, but a few have more. In Utqiaġvik, 232 of 239 recorded breeding attempts were with one mate. On Baffin Island, one male bred with two females. On Fetlar, a male bred with two females, one younger and possibly his own daughter. There are also unconfirmed cases of polyandry, where one female was fed by two males. Snowy owls can breed once a year, but many do not try when food is scarce. They wander widely in search of food, yet they keep a stricter breeding season than short-eared owls. Nine radio-tagged females near Bylot Island searched for an average of 36 days before breeding. A breeding territory usually covers about 2.6 km² (1.0 sq mi), as on Baffin Island and Ellesmere Island. It is larger when food is short and can reach 22 km² (8.5 sq mi) on Southampton Island. Males mark their territory with song and display flights, with wings held in a dihedral. These flights are somewhat like those of a moth. During courtship, a male often carries a lemming in his bill and bows, though sometimes he uses another prey, such as snow buntings. The nest is usually a shallow hollow on a windy high spot in open tundra. It is typically dry and snow-free, with a good view. Nests may be on ridges, elevated mounds, high polygons, hummocks, hills, human-made mounds, or sometimes rocky outcrops or gravel bars. The female does most of the work, digging a bowl with her claws over about three days, but she does not add materials. Nest scrapes were smaller in Hooper Bay. Occasionally, owls use old nests of rough-legged buzzards or abandoned eagle nests. Because they do not nest on cliffs, they do not directly compete with other large birds. Geese, ducks and shorebirds sometimes gain some protection by nesting close to snowy owls, though the owls will sometimes attack them. Egg-laying usually begins in early May or in the first 10 days of June. Clutches average about 7 to 9 eggs, with up to 15 or 16 in extreme cases. On Victoria Island, the average was 9.8 eggs in a good year. The glossy white eggs are laid on the ground, and the female alone incubates them for about 31.8 to 33 days.

Males bring food to the nest, and extra food is stored nearby. Females develop a large brood patch, a featherless area of skin that helps keep eggs and chicks warm. The female broods the young and may shelter them under her wings in bad weather. Parents defend their nests fiercely, and males usually do most of the defending. They may also attack animals such as caribou in Utqiaġvik, as well as glaucous gulls, arctic foxes, and dogs. In Lapland, Sweden, 77% of 45 distraction displays were made by females. In these displays, the owl acts as if it has a broken wing to lure predators away from the nest. Chicks are semi-altricial, which means they are helpless and blind when they hatch. Food is sometimes stored in caches near the nest, and these may hold more than 80 lemmings. After about two weeks, the chicks begin to walk around the nest site. They leave the nest between 18 and 28 days old but cannot yet fly. They can fly well by 50 to 60 days old. Parental care lasts 2 to 3.5 months. Snowy owls reach sexual maturity the year after they hatch, but first breeding is normally at the end of their second year. They are inconsistent about breeding each year. Nesting success can reach 90–100% in high lemming years. The main causes of nest failure were starvation and exposure. In Norway and Finland, some nests failed due to severe black fly parasitism.

Longevity

Snowy owls live long lives compared to many other birds. In captivity, the oldest snowy owls can live to 25 or even 30 years old. In the wild, they typically live around 10 years. The longest known wild snowy owl was banded in Massachusetts and found dead in Montana 23 years and 10 months later. The yearly survival rate for twelve females on Bylot Island was estimated at about 85 to 92.3%.

It is often reported that snowy owls frequently starve, but studies show they often have enough food to survive the winter. Small radio-tracking and banding studies in the northern Great Plains and the valleys of the northwestern United States support this. Of 71 dead owls found in winter in the northern Great Plains, 86% died from traumas, such as collisions with cars and other objects, electrocutions, and shootings. Only 14% died from apparent starvation. Some owls with healed fractures survived their injuries. In a study of 537 wintering birds in Saskatchewan, researchers looked at fat reserves and found that females had more than males, and adults had more than young birds. Most owls brought to Wildlife rehabilitation centres were male. Other owls died from illnesses such as pneumonia, Staphylococcus, and Aspergillosis. Young owls in Utqiaġvik that left their nests during very long rains were vulnerable to starvation, hypothermia, and pneumonia. Snowy owls may be hit harder by blood parasitism than other birds of prey because of lower immunity. They also have fewer chewing lice than other large owls, with about 3.9 per bird compared with 7.5 for great grey owls and 10.5 for great horned owls in samples from Manitoba.

Status

The number of snowy owls depends on how much food is available. In years with many lemmings, they can seem quite common. Counting them is hard, even over decades, because adult owls move around a lot. The population in Scandinavia has long been thought to be very small and ephemeral, with Finland holding 0–100 pairs, Norway 1–20 pairs, and Sweden 1–50 pairs. In November 2025, the Swedish Species Information Centre proposed classing the snowy owl as "extinct" in Sweden, since no nesting has been seen since 2015, and Birdlife reached the same view. A low breeding population in European Russia has been estimated at 1,300–4,500 pairs, and Greenland has 500–1,000 pairs. In Europe the owl is classed as 'Least Concern', but that assessment has not been updated since 18 December 2020.

Across the world, the snowy owl population is now believed to be much smaller than once thought. Earlier estimates of 200,000–290,000 birds were later found to be far too high, and there are now thought to be only 14,000–28,000 mature breeding pairs. Better surveys, phylogeographic data and a better understanding of the owl's wandering have helped scientists make more precise estimates. Because the population is small and falling, the IUCN moved the snowy owl up to vulnerable species in 2017. The North American population is thought to have dropped by 52% since the 1960s. Snowy owls are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), which means trade in them, including their parts, is regulated. Human activity also puts owls at risk. Many are hit by birdstrikes near busy airports, and others are hit by cars, caught in entangled wires, or affected by pesticides. In Siberia, they are often caught in baited fox traps, and Warfarin poisoning from rodenticides kills some. Snowy owls were once among the most hunted owls, and Circumpolar peoples hunted them for food. Many were shot in Ontario, and some are poached. Disturbance from recreation, reindeer husbandry, motorized traffic and radio-tagging may also be concerns. Mercury has been found in owls in the Aleutian Islands through bioaccumulation, though it is not known whether fatal mercury poisoning has occurred. PCBs may have killed some owls. Climate change is widely seen as perhaps the main reason for the decline, because it affects lemmings and, in turn, the owls. In northern Greenland, lemming numbers fell sharply between 1998 and 2000, and owl productivity dropped by 98%. This is almost certainly linked, and stoats, long-tailed jaeger and Arctic foxes also declined, though less. Warming may also add risks such as hyperthermia, and climate change is a matter of concern for the lemming population cycle, which seems to have been abandoned in Greenland.

In popular culture

• The Harry Potter books by J. K. Rowling, and the films based on them, feature a female snowy owl named Hedwig, who is the pet of the main character. Some people in the media worried that the popularity of the Harry Potter films would lead to more snowy owls being illegally traded as pets. However, there was no strong evidence of more snowy owls being taken from the illicit owl trade, even though more snowy owls than usual were reported at wildlife centres.
• The snowy owl (harfang des neiges in French) is the bird symbol of Quebec.