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Snowy owls are the largest bird species in the Arctic. Snowy owls are predominantly white with dusky brown spots and bars. Females tend to have more markings than males, which may become nearly completely white as they age. Young snowy owls are generally darker and more heavily marked than adults. Snowy owls have yellow eyes and their legs and feet are covered in white feathers that protect them from the cold weather.
Snowy owls are generally solitary and territorial. Territory size varies with prey abundance; during years of abundant prey, as many as five pairs may hold territories within a square mile whereas pairs are much more widely spaced during years of scarcity. Snowy owls are migratory. However, migration in this species is unpredictable and likely related more to prey abundance than seasons or weather. In general, snowy owls move nomadically and breed when and where prey is abundant. Unlike most owls, snowy owls are largely diurnal, or awake, during the day.
Snowy owls are carnivorous. They hunt by utilizing an elevated perch that provides them good visibility while waiting for potential prey to appear in the hunting area. Visual scanning of the hunting area is facilitated by their ability to swivel their head 270 degrees around. Their main prey is typically lemmings and mice, however, they also take rabbits, seabirds and fish opportunistically. Like other birds of prey, snowy owls regurgitate a small pellet containing undigested bones and hair after they eat.
Snowy owls are generally monogamous and usually breed between May and September. Individuals arrive on the breeding grounds beginning in late April, though breeding pairs may form earlier on the wintering grounds. The male of a pair establishes a territory and the female selects a nest site. The female constructs a nest by scraping out a shallow bowl in the turf or bare ground. The nest is not lined with any insulating materials. Clutch size is usually three to eleven white eggs depending on prey availability, but can be as large as 16 when prey are extremely abundant. Incubation by the female lasts 32 to 34 days. Both parents feed and protect the chicks which are covered with snowy white down. Chicks begin to leave the nest before they can fly, 14 to 26 days after hatching. The parents continue to feed them for five to seven weeks until they are able to hunt for themselves.
Adult snowy owls are able to breed annually if prey abundance allows. In years of low prey abundance, snowy owls forgo breeding. Snowy owls generally raise only one brood per breeding season. However, if a nest fails early in the breeding season, snowy owls may re-nest.
The global population of snowy owls is estimated at about 290,000 individuals and appears to be stable. They are protected under the Migratory Bird Treaty Act. The most common causes of mortality of snowy owls include collisions with vehicles, utility lines, airplanes, gunshot wounds, electrocution and entanglement in fishing tackle.
The Cornell Lab of Ornithology
University of Michigan Museum of Zoology Animal Diversity Web
Alaska Department of Fish and Game