Snowy owl migration gives scientists chance to study them
CHICAGO — Scott Judd trained his camera lens on the white dot in the distance. As he moved up the Lake Michigan shoreline, the speck on a breakwater came into view and took his breath away: it was a snowy owl, thousands of kilometres from its Arctic home.
“It was an amazing sight,” said Judd, a Chicago IT consultant. “It’s almost like they’re from another world. They captivate people in a way that other birds don’t.”
The large white raptors have descended on the Great Lakes region in Canada, including around the Hamilton area and Northeastern United States in huge numbers in recent weeks, hanging out at airports, in farm fields, on light poles and along beaches, to the delight of bird lovers.
But for researchers, this winter’s mass migration of the owls from their breeding grounds above the Arctic Circle is serious business.
It’s a chance to trap and fit some of the visitors with tiny transmitters to help track them around the globe and study a long-misunderstood species whose numbers likely are far fewer than previously thought, researchers say. “There is still a lot that we don’t know about them … but we aim to answer the questions in the next few years,” said Canadian biologist Jean François Therrien, a senior researcher at Hawk Mountain Sanctuary in Pennsylvania.
The solar-powered transmitters can last for years, collecting information such as latitude, longitude, flight speed and air temperature that is downloaded to a server when the birds fly into range of a cell tower.
The use of transmitters, which intensified during the last North American mass migration in winter 2013-14, already has yielded big surprises.
Instead of 300,000 snowy owls worldwide, as long believed, researchers say the population likely is closer to 30,000 or fewer. The previous estimate was based on how many might be able to breed in a given area.
That calculation was made assuming snowy owls acted like other birds, favouring fixed nesting and wintering sites. But researchers discovered the owls are nomads, often nesting or wintering thousands of miles from previous locations.
The miscalculation doesn’t necessarily mean snowy owls, which can grow to about two feet long with five-foot wingspans, are in decline. Scientists simply don’t know because they never had an accurate starting point.
This month, snowy owls were listed as vulnerable by the International Union for Conservation of Nature. They’re protected in the United States under the Migratory Bird Act.
This year’s mass migration is a bit of good news. Researchers once thought these socalled “irruptions” signalled a lack of prey in the Arctic, but now believe the opposite. Breeding owls feed on lemmings, a rodent that lives under Arctic snowpack and whose population surges every three or four years. More lemmings mean the owl population explodes — and that more birds than usual will winter in places people can see them.
But researchers worry that climate change will affect the owl population because lemmings are exceptionally sensitive to even small temperature changes.
Lemmings “depend on deep, fluffy, thick layers of insulating snow” to breed successfully, said Scott Weidensaul, director at Project SNOWstorm, an owl-tracking group whose volunteers have put transmitters on more than 50 snowy owls in the past four years.