Young Snowy Owls sometimes disperse long distances. Seven Snowy Owls from the same nest were banded on Victoria Island in the Arctic Archipelago, Canada, in 1960. Within a seven-month time span beginning in the following year, two were recovered in Ontario, Canada, and one on Sakhalin Island, former USSR.
The breeding range of the Snowy Owl is circumpolar, ranging across the northern regions of Greenland, Scandinavia, Russia, Alaska, and Canada. In North America, winter irruptions bring Snowy Owls into southern Canada about once every four years. During irruptive years that occur unpredictably across different parts of the continent, Snowy Owls may winter as far south as the northern and central United States, especially the Great Plains, and sporadically as far south as central California, Texas, and Florida. These irruptions are believed to be related to the boom and bust cycles of lemmings, the Snowy Owl's main prey, and other factors such as weather.
In the frozen landscape of the arctic tundra, the Snowy Owl's fate is often tied to the abundance of lemmings. In a good year, a pair of Snowy Owls may raise a dozen nestlings, feeding them some 2,000 lemmings before the young can hunt on their own. In contrast, in years when lemmings are scarce, Snowy Owls may not even attempt to breed. Fluctuating prey availability and weather conditions influence the whereabouts of this nomadic species during the breeding season as well as winter. On Banks Island in Canada, the breeding population ranged from 2,000 to 20,000, depending on the year.
Snowy Owls breed on the open tundra where hummocks, hillocks, or boulders serve as perching and nesting sites. The male courts the female with both aerial and ground displays. He rises into the air with exaggerated wingbeats and undulating flight, holding a lemming or other prey in his bill or with his claws. He descends to the ground with wings flapping or held in a "V." He drops the prey on the ground, stands erect, then lowers his head and fans his tail as the female approaches. For a nest, the female scrapes out a patch of turf or bare ground with her feet. In the unlined nest, she may lay three to five eggs when food is limited, or as many as a dozen when food is abundant. The female incubates the eggs alone. She broods and feeds the young, supplemented with food brought by the male. The young leave the nest about 25 days after hatching, but their parents continue to feed them for at least another five weeks.
Given the opportunity, Snowy Owls will eat lemmings almost exclusively. Where lemmings are unavailable, Snowy Owls will hunt other small mammals and birds, including rodents, rabbits, squirrels, songbirds, waterfowl, wading birds, and alcids such as murrelets. John James Audubon observed a Snowy Owl lying down with head and belly on the snow at the edge of an ice hole, where it waited for fish and caught them using its feet.
Standing nearly two feet tall and weighing about four pounds, the Snowy Owl is North America's heaviest owl. The plumage of the Snowy Owl is largely white, with variable amounts of brown barring and spots. Adult males can be entirely white, but some males have sparse brown or gray barring on the breast, back, wings, head and/or tail. Females are larger than males and generally have more barring than males, although plumage can look similar depending on the individuals. First-year Snowy Owls are more heavily barred than adults. Adult females tend to winter farthest north, and immature males farthest south. Males hoot more often than females. The typical "hoo hoo" has variants including a single long "hoo" or six or more "hoo's" in a row, with the last one the loudest. Snowy Owls are largely diurnal and often perch from the highest points in open habitat, including buildings and telephone poles in settled regions. They are sometimes seen on beaches and at airports during winter irruptions.