Forty below and deep snow? For some Arctic owls, the extreme environment calls for an occasional journey south of the border
- Cynthia Berger
- Feb 01, 2004
DRIVING FOREST ROADS in winter, Manitoba biologist Jim Duncan will often spot a great gray owl sitting motionless in a roadside tree, staring at the ground with round, yellow eyes. "You look where the owl is looking," says Duncan, manager of biodiversity conservation with Canada’s Manitoba Wildlife Branch, "and all you see is a blanket of snow." Yet suddenly the bird launches from its perch, folds its wings and plunges headfirst toward the ground. "You think it’s committing suicide," he says.
Snow plunging looks like a desperate act, but it’s the opposite of suicidal—it’s how great gray owls make a living in the icy north. These owls—the largest in North America, reaching 33 inches in length—are diving after small rodents, mostly meadow voles that hunker in burrows beneath the snow.
Great grays aren’t the only owls that hunt prey like kamikaze pilots. Joining them in their maneuvers are northern hawk owls and boreal owls, which share the great gray’s boreal-forest range in northern Canada and Alaska and sometimes the high-elevation conifer forests of the American Rockies, Cascades and Sierras, and snowy owls, which live farther north above the Arctic Circle on the treeless tundra.
These owls share several other adaptations to their extreme environment, such as fluffy feathers that extend over vulnerable ankles and toes in subzero weather and plumage that makes them immune to the cold. The snowy’s outermost feathers, for example, are unusually stiff. Experts speculate that they function like a nylon jacket over polar fleece, blocking the tundra wind. "You’ve got to be impressed when you see a snowy owl sitting 100 feet up on a metal hydropole in a wind chill of 60 below," says Duncan. "If you left your car without a coat in that weather, your skin would freeze in less than a minute. This bird just sits up there, looking happy as a lark."
Photo: © WAYNE LYNCH
THIS NORTHERN HAWK OWL nabbed a mouse in a forest in Alberta, Canada. The long-tailed owl—which is hawklike in shape and behavior—later stashed its furry meal in a nearby tree hole for future consumption.
But the adaptation that most excites bird-watchers is when these owls start showing up in unexpected places. Scientists call these mass movements to the south irruptions because—unlike long-eared and short-eared owls, which breed in some of the same regions—these owls don’t migrate. Irruptions happen periodically, perhaps once every three to five years, most likely prompted by food shortages.
As dietary specialists, all four species of Arctic owls favor a particular prey species. Great grays and northern hawk owls prefer meadow voles, boreals focus on red-backed voles, and snowies primarily eat lemmings. "When the meadow vole population crashes every three to five years," says Duncan, "there are still plenty of other prey a great gray could take—thousands of red-backed voles, grouse, hare—but for some reason these birds are not wired to take them."
They are not like great horned owls, for example, which also inhabit—and stay put in—the great white north because they can dine on some 200 different prey species. Boreal and northern hawk owls do catch and stash extra dead rodents in handy tree crotches to eat later, when pickings are slim—the birds sit on frozen carcasses to thaw them first. But when things get desperate they head south in search of food.
Records of owl wanderings southward date back to 1831, when John James Audubon hurried to Marblehead, Massachusetts, hoping to see an errant great gray. (Unfortunately for the famous artist and naturalist, the owl died before he arrived.) During irruption years, snowy owls have been sighted as far south as North Carolina and Utah. During the irruption of 1986–87 observers counted 23 snowies in a single day at Boston’s Logan Airport. In the great gray owl irruption of 2001, birders in southeastern Manitoba spotted more than 100 in a single day.
Photo: © WAYNE LYNCH
AS THIS BROOD of boreal chicks matures, they will exchange their distinctive chocolate feathers for gray ones, coming to resemble saw-whet owls, their close—and far more common—cousins.
Given that northern owl populations naturally experience large fluctuations in size, it’s hard for wildlife managers to determine whether species are stable or struggling.
To further complicate matters, the main source of data on North American bird population trends, the volunteer-based Breeding Bird Survey (BBS)—a collaboration between U.S. Geological Survey and the Canadian Wildlife Service—collects almost no data on northern owls. Relatively few humans, much less willing volunteers, live in the Canadian regions where these owls breed.
Recognizing the need for owl population data, the nonprofit Bird Studies Canada launched an national, annual nocturnal owl survey in 2001, relying on volunteers to do the actual fieldwork. "There just aren’t enough scientists to cover such a vast area," says Lisa Takats Priestley, the prairie Canada program manager for the organization.
In 2002, 867 Canadians counted owls from March through April (the owl breeding season), driving along forest roads and stopping to listen for owls at 10 regularly spaced monitoring stations.
"It’s quite exciting to do a survey," says Priestley. "It’s not just that you hear owls, but the whole experience—being out at night, seeing the northern lights, seeing flying squirrels and other nocturnal critters or hearing wolves howling—that really gets your heart going."
In the United States, data on northern owl populations are being collected through the survey and management program of the Bureau of Land Management’s (BLM) Northwest Forest Plan, which requires land managers to assess potential impacts on rare and sensitive species whenever timber sales are proposed in old-growth forests. In May 2003, however, the Forest Service and BLM proposed eliminating some of the survey requirements. At presstime a decision was still pending.
With scientists unable to get a fix on owl numbers, conservationists worry that loss of habitat—whether from natural disasters or human actions such as logging—could seriously harm owls without anyone noticing.
"Great grays often nest in the tops of dead snags, so they require fairly good-sized trees," says Priestley. Boreal owls nest in cavities excavated by pileated woodpeckers and northern flickers and also require big, old trees. The problem is that big trees also attract timber companies. A recent report published in Conservation Ecology predicted that most of the old-growth boreal forest in western Canada will be completely gone by 2065 if logging and drilling for oil and natural gas continue at current rates.
In treeless Barrow, Alaska, where snowy owls congregate during the breeding season, logging isn’t an issue, but urban sprawl is. Increasingly, people are encroaching on the bird’s high-tundra breeding grounds. Also, though all owls are protected in North America under the Migratory Bird Treaty Act, it’s legal in Alaska for all residents to shoot snowies as long as the owls are eaten or used for clothing—not sold. The owls are a traditional subsistence food for the native Inupiat. In fact, Barrow is also known as Ukpeagivk, which means "where owls can be hunted."
"As far as we know, no one is actually eating snowy owls anymore in Barrow—but they are still killing them," says Denver Holt of the nonprofit Owl Research Institute in Charlo, Montana, who has seen radio-tagged birds shot and left for dead at his Barrow study site.
Then there is always the havoc that nature itself can wreak. In 2001, a major windstorm bowled over 200,000 acres of Minnesota forest. Bill Lane, an independent wildlife consultant and surveyor of boreal owl populations in the state for almost two decades, speculates that old trees were disproportionate casualties of the storm. In the western United States, researcher Greg Hayward says, the massive forest fires in the summer of 2000 burned up large areas of mature spruce-fir forest, prime habitat for invading boreal owls and the small population that lives there year-round. "These sites probably won’t have boreal owls in them for 50 to 100 years," he says.
Will U.S. residents see northern owls wander south this winter? The experts are loathe to predict; small mammal population cycles are notoriously erratic. "But we have seen very high owl reproduction rates here in Manitoba the last two years," says Duncan. That could mean conditions are right.
"I think one of the most striking things about an owl irruption," he adds, "is the reaction of the public. All of a sudden, people who never even thought about watching birds are calling us, wanting to help with our research. To me, that is one of the rewards of my work—to see people so excited by these beautiful birds."
Cynthia Berger writes from central Pennsylvania.
Finding food isn’t easy in the great gray owl’s geographic range—the band of boreal forest that girdles the top of the globe. Here, winters are long, cold and dark.
Though owls are famous for their keen vision in low-light conditions, that doesn’t mean they can see through snow. Great grays can, however, detect faint squeaks filtering through as much as two feet of the white stuff from as far as 30 yards away—thanks to exquisitely sensitive ears positioned asymmetrically on the skull.
Plummeting headfirst toward its target, a great gray thrusts its long legs forward at the last minute so it strikes the snow with powerful feet rather than its head. It can punch through an ice crust that is half an inch thick and is capable of supporting the weight of a 185-pound scientist. Then it sifts through the snow with its toes to come up with a vole in its talons.
"Great grays are the gold medal champions of snow plunging," says Jim Duncan, though accidents do happen. The manager of biodiversity conservation with Manitoba’s Wildlife Branch once found a radio-tagged owl, dead, with its wing wedged in the fork of a shrub. He speculates the owl didn’t see the trap when it plunged and, once caught, couldn’t brace its feet to lift the wing out.
Boreal Means Bird
Next time you spot a warbler during spring migration, give a nod of appreciation to the immense boreal forest that stretches across the top of North America from Alaska to Newfoundland. One of the largest intact forests on the planet—the size of more than 10 Californias—it’s the breeding ground for nearly 290 species of birds, including the owls on these pages. In fact, one in three of the birds you see migrating through the United States breed in this mosaic of trees, lakes, river valleys, wetlands, peatlands and tundra. Most are landbirds but others, such as common loons and whooping cranes, depend on boreal lakes for breeding and staging habitat.
Today this largely untouched haven is under threat from logging, mining and drilling for gas and oil. Says Gaby Chavarria, policy director of wildlife conservation at NWF, "Protecting the wintering grounds for migratory species within our borders is important, but we also have to secure the safety of nesting grounds to our north." For more inforation about the boreal forest and what you can do, visit www.borealbirds.org.
Helping the Birds of the Boreal Forest
Billions of birds rely on the boreal forest—the sweeping expense of trees across Canada—for critical breeding grounds and summer residences. Unfortunately, clear cutting is taking its toll, as environmentally sound forestry practices are not commonplace here.
Much of the resource development in the boreal is spurred by the United States, which is the leading importer of Canadian wood products. Driving the demand for cheap pulp is junk mail, advertising inserts, newsprint, toilet paper, magazines and catalogs. In fact, according to the American Bird Conservancy, more than a third of all newsprint used in the United States originates from boreal forests.
Protecting these forests requires action on many fronts. Some retail companies such as IKEA, The Home Depot and Staples, have already vowed to avoid purchasing wood products from there.
You can do something, too. Besides seeking out products made from post-consumer recycled paper, recycling and being resourceful with the paper products you absolutely have to have, call or write to the magazines, newspapers and catalogs that you receive and tell them you want them to print only on post-consumer recycled paper. Or request delivery of these publications in electronic format, when available. Then sit back and enjoy all the warblers, finches, flycatchers and sparrows that fly back to your yard this spring, and know that you worked to help them make it.—Heidi Ridgley
Researchers and bird watchers know that every few years owls that live north of the Lower 48 sometimes show up in odd places. The birds have been found to travel 12 to 161 miles outside their territory during these periods known as eruptions, which are most likely caused by food shortages. But in 2000, a northern hawk owl made avian history.
That October, someone called the staff at the Togiak National Wildlife Refuge in Dillingham, Alaska, to report a dead hawk. Wrapped on the bird’s leg was a band matching the number that was placed on a northern hawk owl in Alberta, Canada, in February—some 1,980 miles away. By all accounts it’s a remarkable journey for a species regarded as nonmigratory.
The only other owl to come close—since such movements were tracked—was a northern owl in Europe that journeyed 1,116 miles. But that’s still 864 miles less than North America’s travel champion. —Heidi Ridgley