Twelve Owls

Snowy Owl

O ne of the most famous owls in the world is a fictional character: Harry Potter’s Hedwig. In J. K. Rowling’s novels, Hedwig is a female, but the birds chosen to portray her in the movies have all been males. Healthy female Snowy Owls can tip the scales at over five pounds, while males weigh less than four pounds—a hefty difference that was especially significant in the early films when young Daniel Radcliffe had to carry Hedwig on his arm. Adult male Snowy Owls have another advantage in a movie about a magical world: their gleaming white plumage looks striking against black wizard robes. Female and immature male Snowy Owls are barred and speckled with dark brown. In an iconic scene, Hedwig carries Harry’s new broom, a Nimbus 2000, through the Great Hall to him. Could a real Snowy Owl succeed at such a feat? Most corn brooms weigh less than a pound and a half, while snowshoe hares and large ducks, prey for many Snowy Owls, often tip the scales at more than two pounds. So unless a Nimbus 2000’s magical high-speed technology adds significantly to the broom’s weight, it would be easy for a Snowy Owl to carry one. To create the movie scene, however, the owl was filmed flying through, and the broom was added digitally. Real Snowy Owls live in open terrain from just above the tree line to the edge of the polar seas in North America, Europe, and Asia. Every winter, some wander south from Canada and Alaska to the Great Plains, and at least a few appear annually in Minnesota. They can be found anywhere in the state, but the single most reliable place to find them is the Duluth harbor. David Evans, who bands raptors at Hawk Ridge Bird Observatory every autumn, has been studying the Snowy Owls in the Duluth–Superior area every winter since 1974. During the 1970s and early 1980s, when spilled grain from shipments through the harbor supported a large population of Norway rats, the owls were especially abundant; Evans caught and banded one or two dozen every year, and one winter he banded thirty-three. Now that rat numbers are lower, he averages about ten Snowy Owls a year. SnowyOwl • 61 • 62 • Snow y Ow l During some winters, in what we call invasion years, Snowy Owls appear in large numbers throughout the northern and even central United States. Some of these birds are underweight or even starving, but researchers have discovered that most have reasonable fat levels and that some of the starving individuals bear old injuries, usually from collisions with wires or automobiles, which have impaired their ability to hunt. Snowy Owl invasion years tend to coincide with cyclic periods of low abundance for lemmings. These feisty, hamster-sized Arctic rodents form the bulk of Snowy Owl diets; some Snowy Owls eat little else. Ornithologists used to explain owl irruptions as simple cause and effect, and many contended that few of these owls ever return to their Arctic homes because so many apparently starve or are killed while south of their breeding grounds. But banding studies by David Evans and others established that some individual Snowy Owls return to a wintering area year after year, surviving not just one entire season and the return trip to the Arctic but several more. Now ornithologists realize that Snowy Owl distribution is more complex than their original boom-and-bust model explained. The birds that wander the farthest tend to be young males; adult females, the largest and most capable of defending a winter territory against competitors, remain the farthest north. Apparently unless food is abundant, young males are forced to wander when larger, more aggressive Snowy Owls evict them from their winter territories. Once they reach Minnesota, Snowy Owls spend most of their time in open areas, virtually never in forests. On the tundra, Snowy Owls don’t experience branches above their heads. Trees near the tundra tend to be short conifers with branches so densely packed that a four- or five-pound owl can easily sit atop them. Perhaps that’s why when they retreat to Minnesota they rarely sit in trees. The slow but steady northward advance of trees associated with climate change may expand the range of Great Horned Owls at the expense of Snowy Owls. Snowy Owls are adept at grabbing ducks, and whether in the north or south, they gravitate to icy shorelines. Because people...