One of North America’s largest owls, the snowy owl (Nyctea scandiaca) lives in the northernmost part of the world, the arctic tundra. This bird has adaptations and movements that enable it to find enough food and survive in such an extreme climate, where there’s daylight all through the summer and darkness every day of the winter.
How the Snowy Owl is Adapted for Arctic Living
Unlike most other owls, snowy owls are diurnal, meaning they are active mostly in the daytime. They have an upper eyelid that projects to shield their eyes from the strong sun, as the owl relies on its vision when hunting. In the winter, where there is total darkness in the arctic, the owl will adapt and hunt in the nighttime hours.
The fine feathers on the snowy owl’s face, like the large feathers on its body, are surprisingly effective insulation from the extreme cold and roaring winds at that latitude, where the birds must endure temperatures as low as fifty degrees below zero (Fahrenheit). They do not seek shelter from such conditions, their bodies being able to withstand it in the same way as other animals, like the arctic fox.
The Snowy Owl’s Hunting Methods
The snowy owl is a formidable presence on the tundra, feeling no need to hide itself. The female birds are generally larger than the males, weighing up to five pounds. Unlike other raptors, the snowy owl will often hover in the air to look for prey from above the ground, yet spends most of its time sitting quietly in the scrubby vegetation, or perched atop a roof or post, out in the open, to patiently wait for its next meal.
The snowy owl will feed on weasels, foxes, rabbits, rodents—lemmings being their favorite—fish and several kinds of sea birds, such as eiders, gulls, and jaegers. Their keen eyesight and hearing enables them to detect prey from great distances, or when it is under thick grass or a heavy layer of snow.
When the owl has spotted its prey, it will actively pursue it before grabbing it in its strong talons. During breeding season, male snowy owls have been known to establish nests with more than one female, and hunt for food for the chicks in both nests. The owls will be fiercely protective of their young, defending large territories established around both nesting spots.
The Snowy Owl is an Irruptive Species
Like great-horned owls and short-eared owls, the snowy owl depends mostly on rodents for its diet. Some researchers estimate a snowy owl can eat 1,600 lemmings per year. This owl is a bird species that is irruptive, meaning it must migrate to other areas to find adequate food when rodent populations fluctuate. It has been observed that, for the snowy owl, this occurs every three to four years.
While most winters snowy owls will regularly visit the northeastern U.S. states and northern plains states, in irruptive years greater numbers of the owl may be spotted in those areas, and the owl will appear in other places, such as the Pacific northwest, the Midwest and eastern Canada.
The Reason for the Four-Year Cycle
It is no coincidence that, like the snowy owl’s periodic movements, lemming populations follow a four-year cycle, too. Finnish scientists have discovered a link between the lemmings’ numbers and their chief predators, which includes the snowy owl.
Stoats (weasels), foxes and the long-tailed skua (a sea bird) are the other chief predators of lemmings. Knowing that stoats only feed on lemmings, and that their reproductive rate is slower than rodents, the scientists found that the owls, foxes and skuas were responsible for controlling the lemming population throughout the stoat reproductive cycle. Once the stoat numbers reached an adequate level, the lemming population would suddenly decline.
Thus, an irruptive year for the snowy owl follows a lemming population crash, giving birdwatchers in the northern U.S. a greater chance to see this amazing arctic bird—and more of them—while it visits coastal or farmland areas, and demonstrates its skill at hunting for voles, fish, birds, rabbits and other “local fare.”
Sources:
- “About Snowy Owls.” MassAudubon.org. Accessed 19 January 2010.
- Connor, Steve. “Forget the Myths of Mass-suicide: Lemmings Simply Fall Prey to Four Killers.” The Independent, 31 October 2003.
- Warren, Lynne. “Muscle & Magic: Snowy Owls.” NationalGeographic.com. Accessed 20 January 2010.
Cheryl Kraynak - Cheryl Kraynak has worked in publications and communications for 20 years and has expertise in the natural world and creative arts.
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