The Cornell Lab of Ornithology dedicates this account in honor of Hap (Alexander) Ellis, member of the Lab of Ornithology's Administrative Board.
The Snowy Owl, also known as the Arctic Owl or White Owl, nests on Arctic tundra habitats throughout its northern circumpolar breeding range—often adjacent to coastal Arctic seas. This is one of the largest owls in the world, and has the most northerly breeding and wintering distribution of any owl species.
Plumage is unmistakable in this species. Adult males are almost pure white, and adult females are white with brown barring. Females are distinctly larger than males. Young males resemble adult females, but have more spotting on their flight feathers; it may take many years for males to acquire their nearly pure white adult plumage. Females are believed to become somewhat whiter with age but they maintain distinct brown bars throughout their lives. It remains unknown at what age adult definitive basic plumage is reached for either sex, or when Snowy Owls breed for the first time.
During winter this owl can be solitary, maintaining individual territories, or social and share communal roosting areas. Except for people living in Arctic environments, most Snowy Owls are seen only on their southern wintering grounds. Many adult Snowy Owls, however, winter on or near their breeding grounds, while other adults and younger owls winter regularly on the prairies of southern Canada, in the northern United States, and sporadically further south.
Snowy Owls are also nomadic and irruptive migrants, and at times can appear almost anywhere, often in surprising abundance. Only rarely are the irruption migrations continent-wide (e.g., during the winter of 2011–2012; see Distribution: Winter Range). These mass movements are unpredictable, and the reasons driving this behavior remain unclear. The preponderance of young owls often seen in these irruptions suggests that unusually successful breeding (large fledging brood sizes) may be a factor, combined with declining food supplies (primarily lemmings).
Satellite tracking studies have confirmed what many native and northern peoples have known for centuries - some Snowy Owls spend the winter in the Arctic darkness. The owls often winter near villages, open leads, open water within the ice pack, and even polynyas far out to sea. Here they are believed to hunt lemmings, hares, ptarmigan, seabirds, sea ducks, and perhaps even to scavenge food killed by other predators.
Satellite studies have also shown that Snowy Owls are capable of long distance east–west movements—e.g., from Alaska to Russia and back, and from Norway to eastern Russia—never moving south for winter but likely in search of adequate food. Other studies from Canada and United States have followed Snowy Owls from their wintering grounds to their summer breeding grounds.
Snowy Owls nest on Arctic tundra, placing their exposed nests on windswept ridges, mounds, hummocks, and rocky outcrops—areas that have little vegetation, where the snow melts early in spring, and where the height of the mounds provides a commanding view of the surrounding country. This is one of the few species of owls that construct a nest; nesting females dig a circular bowl on the ground in which to lay eggs. And this is an owl that may aggressively defend its nest, with males (and sometimes females) fierce in their ability to stave off potential predators. Although the Arctic summer is short, the Snowy Owl breeding season is fairly long, about 4.5 months. Nevertheless, this owl has only one chance to breed per year, and conditions must be right.
This is a large powerful owl capable of killing prey the size of eiders. Throughout most of its breeding range, however, it needs high densities of small, 60–90 gram (2–3 oz.) rodents known as lemmings, in order to breed. Breeding is often a "boom or bust" event, with females producing large clutches and fledging large broods if food is abundant. Although clutches as large as 14–16 eggs have been reported, most large clutches range from 5–10 eggs. When food is scarce, some Snowy Owls produce smaller clutches (4–7 eggs), while some individuals may refrain from breeding altogether that season.
The Snowy Owl is believed to be one of the oldest bird species recognized in prehistoric cave art. Clearly, it must have been admired for many reasons by prehistoric peoples. This owl has also had a long history with native Eskimo people, who collected owl eggs for food, sometimes hunted the young and adult owls, and also honored the bird in carvings of ivory and bone.
Today, the Snowy Owl stands alone as the avian icon of Arctic tundra ecosystems. Indeed, it may be one of the best indicators of the health of Arctic environments and, owing to its many admirable qualities, can play a key role in helping to galvanize Arctic conservation.