The Snowy Owl
Bubo scandiacus – Formerly Nyctea scandiaca
The Snowy Owl was first classified in 1758 by Carolus Linnaeus, the Swedish naturalist who developed binomial nomenclature to classify and organise plants and animals. The name “scandiaca” is a Latinised word referring to Scandinavia, as the Owl was first observed in the northern parts of Europe. Some other names for the Snowy Owl are Arctic Owl, Great White Owl, Ghost Owl, Ermine Owl, Tundra Ghost, Ookpik, Scandinavian Nightbird, White Terror of the North, and Highland Tundra Owl. It is the official bird of Quebec.
Description: The Snowy Owl is a large, diurnal white Owl that has a rounded head, yellow eyes and black bill. The feet are heavily feathered. A distinctive white Owl, their overall plumage is variably barred or speckled with thin, black, horizontal bars or spots. Females and juveniles are more heavily marked than males – adult males may be almost pure white, although they have up to three tail bands. Adult females are distinctly barred throughout, and have from four to six tail bands. Immatures are very heavily barred throughout, and dark spotting may codominate or dominate the overall plumage. Intensity of dark spotting varies with the sex of the immatures, females being the darkest. Juveniles are uniformly brown with scattered white tips of down.
Snowy Owls have a direct, strong, and steady flight with deliberate, powerful downstrokes and quick upstrokes. They make short flights, close to the ground, from perch to perch, and usually perches on the ground or a low post. During hot weather, they can thermoregulate by panting and spreading their wings.
Size: Length 51-68½ cm (20-27″) average female 66cm (26″ inches), male 59cm (23″)
Wingspan 137-164cm (54-65″)
Weight 1134-2000g (40-70oz) average female 1707g (60oz), male 1612g (57oz)
Voice: The Snowy Owl is virtually silent during non-breeding seasons. During the breeding season males have a loud, booming “hoo, hoo” given as a territorial advertisement or mating call. Females rarely hoot. Its attack call is a guttural “krufff-guh-guh-guk”. When excited it may emit a loud “hooo-uh, hooo-uh, hooo-uh, wuh-wuh-wuh”. Other sounds are dog-like barks, rattling cackles, shrieks, hissing, and bill-snapping.
Nestlings “cheep” up to 2 weeks of age, then hiss and squeal.
Hunting & Food: Most hunting is done in the “sit and wait” style, swivelling the head as much as 270 degrees scanning for prey. These Owls are highly diurnal, although they may hunt at night as well. Prey are captured on the ground, in the air, or snatched off the surface of water bodies. When taking snowshoe hares, a Snowy Owl will sink its talons into the back and backflap until the hare is exhausted. The Owl will then breaks its neck with its beak. Snowy Owls will often raid traplines for trapped animals and bait, and will learn to follow traplines regularly. They also snatch fish with their talons. Small prey up to small hares are swallowed whole, while larger prey are carried away and torn into large chunks. Small young are fed boneless and furless pieces. Large prey are carried of in the Owl’s talons, with prey like lemmings being carried in the beak.
Snowy Owls are mainly dependent on lemmings and voles throughout most of their Arctic and wintering range. When these prey are scarce they are an opportunistic feeder and will take a wide range of small mammals and birds. Some mammal prey include mice, hares, muskrats, marmots, squirrels, rabbits, prairie dogs, rats, moles, and entrapped furbearers. Birds include ptarmigan, ducks, geese, shorebirds, Ring-necked Pheasants, grouse, American coots, grebes, gulls, songbirds, and Short-eared Owls. Snowy Owls will also take fish and carrion.
Some nesting Owls switch from lemmings and voles to young ptarmigan when they become available. Snowy Owls do not hunt near their nests, so other birds, such as Snow Geese, often nest nearby to take advantage of the Owls driving off predators such as foxes.
Snowy Owls produce large, rough-looking cylindrical pellets with numerous bones, feathers, and fur showing. They are usually expelled at traditional roosting sites and large numbers of pellets can be found in one spot. When large prey are eaten in small pieces with little roughage, pellets will not be produced.
Breeding: Courtship behaviour can begin in midwinter through to March and April, well away from breeding areas. Males will fly in undulating, moth-like flight when females are visible. On the ground males will bow, fluff feathers, and strut around with wings spread and dragging on the ground. Males kill and display prey in caches to impress females, often feeding the female. The Snowy Owl nests almost exclusively on the ground, where the female makes a shallow scrape with her talons on top of an elevated rise, mound, or boulder. Abandoned eagle nests and gravel bars are used occasionally. Nests may be lined with scraps of vegetation and Owl feathers. Nest sites must be near good hunting areas, be snow-free, and command a view of surroundings. There is little breeding site-faithfulness between years or mates in some areas, but in other areas, a pair of Owls may nest in the same spot for several years. Territories around nests range from 1½ to 6½ square kilometres (0.6 to 2½ square miles), and overlap with other pairs.
Breeding occurs in May, Clutch and brood sizes are heavily dependent on food supply. Snowy Owls may not nest at all during years of low lemming numbers. Clutch sizes normally range from 5 to 8 white eggs but may be as many as 14 eggs during high lemming years. They are laid at approximately 2 day intervals. The female incubates while the male brings her food and guards the nest. Eggs hatch in 32-34 days at two day intervals, leading to large age differences in nests with large clutch sizes. Young are covered in white down. Young begin to leave the nest after about 25 days, well before they can fly. They are fledged at 50 to 60 days. Both parents feed and tend the young, and are fiercely protective and may attack intruders up to 1 kilometre (0.6 miles) from the nest! Nestling Owls require about 2 lemmings/day and a family of Snowy Owls may eat as many as 1,500 lemmings before the young disperse. Snowy Owls are single brooded and likely do not lay replacement clutches if their first clutch is lost. Almost 100% nesting success can be achieved during good vole years.
Numbers fluctuate wildly, usually in concert with lemming and vole numbers. For Example, Banks Island may have 15,000 to 20,000 Snowy Owls during good lemming years and only 2,000 during low lemming years with densities ranging from 1 Owl per 2.6 square kilometre (1 Owl per square mile) in good lemming years to 1 Owl per 26 square kilometres (1 Owl per 10 square miles) in low lemming years.
Mortality: Snowy Owls can live at least 9½ years in the wild and 35 years in captivity. Natural enemies are few – Arctic foxes and wolves prey apon them on their tundra breeding grounds, while skuas and jaegers may take eggs or chicks.
Habitat: The Snowy Owl is a bird of Arctic tundra or open grasslands and fields. They rarely venture into forested areas. During southward movements they appear along lakeshores, marine coastlines, marshes, and even roost on buildings in cities and towns. In the Arctic, they normally roost on pingaluks (rises in the tundra) and breed from low valley floors up to mountain slopes and plateaus over 1,000 meters (3,000 feet) in elevation. When wintering in the Arctic, they frequent wind-swept tundra with little snow or ice accumulation. At more southern latitudes they typically frequents agricultural areas.
Distribution: Circumpolar – Arctic regions of the old and new worlds.
North America – Snowy Owls breed in the western Aleutian Islands, and from northern Alaska, northern Yukon, and Prince Patrick and northern Ellesmere islands south to coastal western Alaska, northern Mackenzie, southern Keewatin, extreme northeastern Manitoba, Southampton and Belcher islands, northern Quebec and northern Labrador. The Snowy Owl is highly nomadic. During periods of lemming and vole population crashes in the Arctic, or excessive cold and snow in winter, mass movements of Snowy Owls occur into southern Canada and northern United States. These invasions occur every 3 to 5 years, but are highly irregular. Adult females stay furthest north while immature males move furthest south during these incursions. In some years small numbers may reach as far south as central California, southern Nevada, Utah, Colorado, Oklahoma, central and south eastern Texas, the Gulf States and Georgia.