6 Facts About the Majestic Snowy Owl

Lovers of the majestic snowy owl can hit the avian lottery if they're lucky enough to witness what's known as an irruption; a periodic phenomenon when hordes of mostly young snowy owls 4-6 months old migrate south from their northern breeding grounds in the Arctic tundra to Canada and the Northern U.S., from as far as Seattle to Boston. When one of these sporadic irruptions occurs, people will flock by the hundreds of thousands to go view these birds in their first year of life, according to Holt. "People who don't have any interest in owls even head out to look at them," he says, "often traveling across state boundaries."

The snowy owls are one of the only owls in the world that display distinct color differences between the male and female. When they're young, they both look like females, which retain brown bars and spots on their white face and plumage throughout their lives, according to Holt. "As the owls age, the females retain most of their darkness, and some males lose their markings almost completely and become a bright fluorescent white. It takes three years for males to become almost pure white." Like the females, however, some male snowy owls never lose their dark bars and spots. "We think that has to do with special selection," says Holt. "Young males that kind of resemble females do not breed; only older males who become bright white at 3 to 4 years old maintain territories and breed."

"Females are more dominant as far as aggression goes, while males are faster and more handsome," says Holt. "Females can weigh 4 to 5 pounds (1.8 to 2.2 kilograms) and males are in the 3-pound (1.3-kilogram) range. The female also has a wing span of about 4.5 to 5 feet (1.3 to 1.5 meters), with the wing span on the male a little less."

"When lemmings are high, snowy owls have a good year," says Holt, who reports that snowy owls in his study range have killed and eaten a total of 45,000 to 50,000 lemmings through the years. "When lemmings are low, they have a bad year, and might refrain from breeding or have a smaller number of chicks." When lemmings are scarce, he adds, they'll switch over to wild birds and shore birds, such as ducks or gulls.

"We think the owls migrate back north to find areas where lemmings are abundant, and then they settle to breed," says Holt. "Once that all starts, males try to entice females to their territories. Only adult white males get to breed, and only if they have a lot of lemmings to offer females; it's all about who's got the resources. Males catch the lemmings, and do an elaborate courtship flight with the lemmings in their bills (flying in an exaggerated undulating pattern, up and down like waves). They land and raise their wings up, turn around and show off their highly reflective fluorescent plumage as if to say, 'Look at me, I'm a handsome male and it's better breeding with me than someone who doesn't even have a house!' You gotta interpret it that way. If he has a good territory and a lot of lemmings, he'll have the opportunity to breed."

When snowy owls return to their Arctic coastal breeding grounds to look for a mate in late April or May, the tundra is still frozen and often snow-covered. "They use their body heat, feet and bills to dig out a bowl about 10 inches (25 centimeters) wide and 3 to 4 inches (8 to 10 centimeters) deep on a high mound or ridge, so the female can lay her eggs," says Holt. "The female will have some 10 to 12 eggs in good lemming years, with the average at around five eggs. After about 32 to 35 days, the eggs will hatch one at a time in the order in which they were laid (or asynchronously, which means you'll have chicks in the nest ranging anywhere from 2 to 10 days old). Only the female incubates the eggs, and the male brings in food and protects her from foxes, polar bears or other predators."