nowy Owl (Bubo scandiacus 0.) Photo by John Hess

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“Up here,” meaning “the High Canadian Arctic, at the north end of Baffin Island, some 700 kilometers north of the Arctic Circle, (latitude 73 degrees north) in a little hamlet called Arctic Bay,” resident Clare Kines reports, ” this was a good summer for lemmings, a very good year. They were everywhere. … Lemmings are the linchpin of terrestrial food chains up here … the daily diet of [Arctic] foxes, ermine, wolves, Rough-legged Hawks, Gyrfalcon and especially Snowy Owls.” And because it was a good year for lemmings, it was a very good year for Snowy Owls, who produced large broods [up to 14]. 

As these broods have grown into juvenile birds there is more and more competition for fewer lemmings and they begin to disperse farther and farther afield, resulting in the irruption that many of you are enjoying now … A brood of nine chicks will be fed something in the order of 1500 lemmings from the time they are hatched until they are independent.”

Lemmings live under the snow in winter, but when snow starts to melt, they sprint over the grassy tundra, easy prey for their quick predators.

High lemming populations occur approximately every four years and then crash. Researcher Charles Krebs postulates that when the lemming population out-produces its food supply, lemming females will kill neighboring young, thus dramatically reducing the population. Formerly, scientists associated Snowy irruptions with lemming crashes, This theory has been turned on its head.

Down here, two Snowy Owls arrived at Montrose Point on Nov. 19, heralding the anticipated “irruption.” According to Christmas Bird Counts between 1952 and 1981, Snowys were seen in Chicago during about 50 percent of those winters, usually in lesser numbers. The last irruption year was 1996-97.

Snowys breed in the northern circumpolar open tundra, between treeline and the shore of the polar seas. During a typical winter, they are nomadic, moving to southern Canada and the northern U.S., particularly the Great Plains. Many are faithful to their wintering grounds. They prefer meadows and airports, any perch that resembles the hummocky open tundra with good sightlines. Being circumpolar, they also winter in Central Europe, Iceland, central Russia, northern China and Japan. This winter is particularly unusual, in that they have been seen across the United States from coast to coast, south to Kansas, and for the first time in Honolulu.

A prehistoric painting of breeding Snowy owls with chicks in the cave of Les Trois Frères in Ariège in the French Pyrenees is considered the first recognizable bird species in cave art. John J. Audubon painted a pair of snowys in 1829, showing the size and plumage differences between male and female. Ironically, he painted them in his only nocturnal scene, although they are known to hunt both day and night. Considering their breeding grounds in the arctic, with 24 hours of daylight, that is not surprising.

J.K. Rowling catapulted the Snowy Owl into fame as Hedwig, Harry Potter’s savior companion. Hedwig is female in the story. In reality, only adult male snowys are white. Females and juveniles are spotted with spotted dusky brown “necklaces” and dark patches on the head; nestlings are dark and spotted. In the films, Hedwig was played by seven different male owls. Males are shorter and weigh about a half-pound less than females, averaging 3.6 pounds, and were considered easier to handle.

Snowys are the heaviest owl on this continent. At an average height of 27 inches, they are large by any standards. Their wing-span can extend to 66 inches. Snowys have rounded heads. Their small ear tufts are usually invisible. Their eyes have golden irises and black pupils and are surrounded by feathers that are long enough to nearly conceal the black bill. Thick feathers almost conceal their legs, toes and claws.

Snowys nest on the ground, often on a hummock, in open, hilly windswept areas that will be free of snow and have an expansive view of the surroundings. The male chooses the territory, the female chooses the nest site and scrapes a simple depression. She may lay eggs up to four days apart, incubating as soon as she lays the first egg. Incubation takes about 32 days and eggs hatch about every two days in the order laid. The male feeds the female during incubation, and both feed the young for about two to three weeks, until they are ready to leave the nest. The young are able to fly at seven weeks and are independent by about ten weeks old. Snowys are considered seasonally monogamous, but some examples of bigamy have been noted. Snowys are extremely territorial and not shy about attacking humans or wolves that approach their nests. Males are the main hooters, particularly when fending off attackers.

Lemmings are their favorite diet, although they will eat hares, voles, shrews, small birds, ptarmigan, Arctic Fox and eggs of waterfowl. Regurgitated pellets the shape of the bird’s gizzard, containing indigestible fur, bones, teeth and feathers, are studied to learn the Snowy diet. In December, 2011, Josh Engel of the Field Museum found two Norway rats, one adult and one youngster, in a Chicago snowy’s pellet.

Snowys are so strikingly exquisite that sighting them is an especially prized experience. Sometimes they perch in the open atop light poles and on piers, scanning for prey. When they perch on the side of stone revetments, as large as they are, their camouflage blends into the light rocks, making them challenging to spot. This year, snowys have been seen in Evanston downtown and on Northwestern’s lakefill. The most reliable place to see them is Montrose Harbor. They should be here through March.

Some words of caution: Snowys on wintering grounds have limited food resources. Getting too close to them for that coveted once-in-a-lifetime photo will make the bird fly and stress it out. Too much stress and the Snowy will lose the energy needed to get back to its breeding ground.

Libby Hill

Libby Hill is the author of "The Chicago River: a Natural and Unnatural History. She has been writing about birds and trees and Evanston's natural history for the Roundtable since 2004.