Handsome visitors from the high tundra.
If you happen to be in one of the northern states this winter, particularly in a low, open prairie or an eastern coastal marsh, you might treat yourself to the sight of some of the most splendid visitors from the Arctic Circle. Dressed in white and seemingly tame, they invariably excite attention and admiration. Inuits know them as ookpikjuak; we call them snowy owls.
These impressive creatures normally inhabit the high tundra, along the northernmost rims of North America and Eurasia, and in the Arctic archipelago almost up to the limit of permanent ice and snow. But many of them spend their winters along the eastern seabord and in the central plains of southern Canada and northern United States, as well as on the steppes and farmlands of Central Asia.
During especially severe winters, snowy owls undertake spectacular mass flights called irruptions. Over North America, these flights may take them as far south as Florida, Alabama, Oklahoma, and central California. Some "snowys" wind up in the Bahamas. Irruptions over Eurasia may lead them to the Caspian Sea, the Balkans, Frnace, and Germany.
Identity and personality
Scientists identify the snowy owl as Nyctea scandiaca, a name that translates prosaically as the "nocturned bird of Scandinavia." It is the world's only large, white owl. The male is about two feet long, with a wingspan of over five feet. The female is about one-third larger than the male, in both size and weight, and is the dominant member of a pair. Among North American owls, the snowy owl is exceeded in weight only by the great horned owl and in size by the great gray owl.
Its unique white garb makes the snowy owl unmistakable in the field, but plumage coloration differs slightly between sexes. The male is almost pure white, with occasional flecks of brown on the wings and shoulders. The females is also white but with more brown flecks that go in waves across most of the wings and breast. For both sexes, the bold eyes are lemon yellow.
The pronounced differences between the sexes, in terms of size and color, are related to their behavioral roles. The male's bright white coast serves as a territorial beacon in the uncertain light of the early summer tundra. By contrast, as the female broods its eggs and young, its patchy plumage helps camouflage the bird in the brown and white background of the tundra's melting snows.
For both sexes, the feathers form a dense covering that extends down to the tips of the talons and almost hides the black bill. Coupled with this insulation is a thick layer of subcutaneous fat, enabling the bird to withstand harsh winters.
Male and female snowy owls may forage for food during any hour of the day or night. They generally go after small mammals, such as lemmings and meadow mice. Occasionally, a few birds are added as they become available. Hunting may involve perching on a low willow or hillock and pouncing when a lemming emerges from its burrow or snowbank. They may also pursue prey on the wing in hawklike fashion.
Snowy owls that winter southward exhibit a more diverse diet: Ducks, seabirds, shorebirds, and various small mammals may be taken. A hungry snowy owl is a formidable predator that easily catches and kills animals much larger than itself. In parts of their winter range, the owls may capture mammals and birds as large as muskrats, jackrabbits, ring-necked pheasants, chickens, geese, turkeys, and great blue herons with equal facility.
When food is scarce, snowys will eat almost anything, including road kill and scraps of garbage. At times, they can be quite resourceful. Naturalist and artist John James Audubon once watched an owl waiting for fish at a hole that fishermen had made in the ice. The bird lay full length on the ice next to the hole, seemingly asleep but raising its head occasionally to look around. Fish that surfaced were quickly snared and eaten, after which the owl resumed its vigil at the hole.
Courtship and breeding
Arriving on their breeding grounds in May and June, snowy owls quickly stake out territories among the heaths and stunted willows of the tundra. Dutch ornithologist Karl Vous has noted that the same territory may be used for many years, apparently by successive generations of birds. Each male claims and advertises its territory mostly by posturing on hillocks and other exposed sites, but also by gliding slowly, showing off its white wing markers far across the tundra. Intruders are quickly targeted and driven away. Sometimes two male owls engage in aerial conflict, locking talons and tumbling through the sky until the intruder gives up and departs.
During courtship, the male tries to impress the female with a low, undulating flight, holding its wings in a shallow V and sky dancing across the thawing tundra. If the female seems receptive the male quickly drops to the ground and dances around, sometimes with a tidbit of lemming in its beak--signaling that it's a good provider. If the female accepts the offer and takes the food, mating follows.
After mating, the female selects the nest site, often atop a hillock or boulder. The bird excavates a small cavity and lines it with moss, grass, and an occasional feather. Depending on the local food supply, the female lays a clutch of 2-6 creamy white eggs, one every two days or so. During years when the lemming supply is low, snowy owls may refrain from nesting, but when lemmings are available in abundance, a big female may lay 8 or 9 eggs. The record is 16 eggs in a single clutch during an exceptional lemming year.
With the female brooding and closely guarding her clutch, incubation takes slightly over a month, and the young hatch at the same intervals in which the eggs were laid. For the first 10 days or so, the owlets are downy white, but then they develop a sooty plumage, which helps hide them among the patches of snow and tundra brown. At this time they can be targeted by jaegers, gulls, and foxes.
Throughout most of the nesting cycle, the male supplies the female with food, enabling the latter to incubate the eggs and feed the young. If the food supply is abundant, the female stores the excess in large piles around the nest. In about two weeks, the oldest of the young leaves the nest and hides nearby, returning when the adults arrive with food.
The young fledge in about 43-50 days, shortly before the onset of fall. For a few weeks after the nesting season, some of the young may remain near the nesting territory, but most wander through the tundra until the onset of winter, then move southward to somewhat warmer habitats. Their life in the wild may stretch for 9 or more years, but most snowys probably survive only half as long. The longevity record is held by a 28-year-old captive bird in the zoo in Basel, Switzerland.
Over much of the circumpolar range, a number of snowy owl populations appear sedentary. If lemmings and other small mammals are abundant, the birds remain on the tundra throughout the year. But recent studies by the U.S. Fish and Wildlife Service in the central and New England states suggest that at least some populations are migratory.
Among southward wintering snowy owls, the first to leave the tundra are adult males and first-year birds. They stake out and defend territories in coastal marshes, corn and wheat fields, and other open expanses that resemble (in plant growth and form) tundra habitats. Some are attracted to airports. They patrol their winter haunts from fence posts, rock piles, and other conspicuous, elevated perches.
The adult females arrive sometime later and, being larger and more dominant, displace the males and juveniles, forcing the latter to find new territories elsewhere. With the arrival of spring, the adults and juveniles begin returning north to their nesting grounds.
The most remote of the snowy owls live so far north that they suffer little, if any, human intervention on their nesting grounds. Toward the southern end of their range, however, these birds and their eggs are frequently food for Inuits. And during their winter migrations, they come in increasing contact with people.
In the early years of this century, local taxidermists made a small fortune every three or four winters, following the irruptive entry of snowy owls into the states. For months at a time, taxidermy shops would display stuffed snowys in theft windows. Under this commercial pressure, few of the owls made it back north to their summer breeding grounds.
Nowadays, with governmental protection extended to snowys, the wintering owls are more likely to be the focus of birders and other wildlife enthusiasts than the target of hunters and taxidermists. But protection has spawned a problem of another sort: the congregation of increasingly abundant owls at airports, where they tend to be a nuisance and sometimes a hazard to aircraft travel. Attempts to displace them from these sites have taught us more than we expected about their intelligence and tenacity. In one celebrated experiment at Boston's Logan Airport, several dummy great horned owls were placed at strategic points around the airport perimeter, in the hope of frightening away the snowys. But the resourceful birds adopted the dummies as hunting and resting perches.
These concerns aside, the snowy owl is a magnificent bird of prey that deserves our admiration and protection. Echoing this, Norman French, who has studied snowys for years in the Boston area, suggests that they serve a valuable function for environmental education, renewed each year with the arrival of the wintering birds.
Dwight G. Smith is professor of biology at Southern Connecticut State University in New Haven. He is a frequent contributor to THE WORLD & I
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|Title Annotation:||snowy owls|
|Author:||Smith, Dwight G.|
|Publication:||World and I|
|Date:||Feb 1, 1998|
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