Snowy Owl Boom: Population of Arctic Birds Soars

  • Closeup of a snowy owl. Photo: Mass Audubon

March 3, 2014

It’s been a big year for snowy owls. People have reported seeing thousands of the magnificent Arctic birds, from Erie, Pennsylvania, to Washington, D.C., all the way to the island of Bermuda. Researchers say there are more owls this season than anyone has seen in 50 years. They call a population boom like this an irruption. The question for many people has been, why is it happening?

The owls started showing up last fall. Most years, bird watchers on Presque Isle, north of Erie, hike out to the easternmost point, and with luck, spot one or two snowy owls. John Laskos says last November, the first owl showed up, then they spotted another.

“Soon there were five, and then there were six, and then there was eight, and then there were up to 13 to 15 snowy owls all at one time at the park.”

Laskos is an environmental educator at the Tom Ridge Environmental Center on Presque Isle.

Snowy owls are adapted to live at the top of the world, in the dark, cold Arctic winter. He says  the unusually high numbers on Presque Isle have encouraged other winter visitors to the area, like photographers and reasearchers.

“The birders, especially, went crazy over this,” Laskos says.  

And it’s not just on Presque Isle.

Ron Cole was among the birders who stopped along a road side south of Jamestown, New York to look at this snoozing snowy, its fluffy white feathers dotted with black, and its sharp yellow eyes.

“Oh, those eyes, those eyes are beautiful! That is a gorgeous bird,” he says.

'Snowies', as they are called,  are among the largest owls, weighing in at around 5 pounds, with a four feet wingspan. They’re known by many because of the fictional character Harry Potter’s pet raptor, Hedwig.

Scott Weidensaul of Millersburg in eastern Pennsylvania has been studying them for many years, and is excited by the numbers, and attention they’re getting this year.

“It’s madness I tell you,” he says.

Weidensaul is a naturalist whose led ground-breaking owl research at the Ned Smith Center for Nature and Art.

“We’re in the middle of what’s known as an irruption. And that’s spelled i-r-r, rather than e-r.”

He says snowy owl irruptions occur every 3 to 5 years. But researchers didn’t expect anything of this magnitude—the large numbers of owls, so widespread across North America.

Weidensaul and a few colleagues started something called Project Snowstorm late last year, to start tracking snowies. He says he’s never been involved in a project that got pulled together so quickly.

“The first week of December, we all kind of looked at each other and said “Oh my God, there’s snowy owls everywhere. This is too good an opportunity to pass up. We very quickly, in a matter of about a week or so, mobilized collaborators across the irruption zone, from New England to Minnesota,” he says.

One of the big questions for researchers has been why so many of these big fluffy raptors have flown south from the Arctic this year.  Henry Tepper is president of Mass Audubon. They’ve long been involved in owl research, in part because so many snowy owls spend time at the Boston Airport. They’ve seen 85 snowy owls so far this winter.

“Some original thinking, and it’s just kind of logical, was that these birds were showing up in the wintertime because they were hungry, because the food supply in the tundra, and the Arctic and the boreal areas is limited. That actually turns out not to be true,” he says.

Researchers say most of the owls they’ve captured are well fed and healthy. Tepper and others attribute this to a population boom in hamster-like rodents known as lemmings in the Arctic during the owls breeding season last year.

“And that resulted in a lot of food supply for snowy owls and therefore very high nesting productivity. So there were a lot of young birds hatched last season. And then what happens is, when winter comes, you have a lot of young birds, and they’re chased off their feeding grounds by adult birds, and they have to range much more widely in the wintertime in search of food.”

That’s the best explanation researchers have so far about why the owls have flown thousands of miles south, showing up in backyards, along roadsides, and at airports. But it begs the question: why were there so many lemmings?

Naturalist Paul Weidensaul says it’s just part of their natural population cycle.

“They boom and bust roughly every four years, and that’s typical of a lot of small rodents up in northern areas. They’re not really quite sure what causes the cycle,” Weidensaul says.

Some researchers think there’s more going on. Lemmings usually burrow in Arctic grasses, hidden by snow. By one theory, warming temperatures and less snow have given them fewer places to hide, and made them easier prey for snowy owls. But Weidensaul wouldn’t connect the owl irruption with warming Arctic temperatures.

“No, no definitely not. I really don’t see any link between this and climate change.”

But some research out of Greenland shows the lemming population is collapsing in parts of the Arctic, and that could be affecting snowy owls.  Other work has described how melting sea ice is making it more difficult for the owls to find ducks, a major source of food in the winter.

Henry Tepper at Audubon understands why some scientists are leary of pegging the snowy owl irruption to climate change.

“We have to be careful about speculation, we have to be careful about thinking we know more, or saying that we know more about these birds than we really do, but we also know what is going on out there, and we also know that the movement of different species is changing, and being disrupted,” he says.

One thing the researchers agree on is there’s a lot to learn about these mysterious raptors, and  this year’s southern travels are providing the best chance yet to study them.

Unlabeled images courtesy of Mass Audubon: (top) an owl at Boston's Logan Airport, where Mass Audubon does nearly all its capturing. (lower) Mass Audubon president Henry Tepper with an owl that's about to be released.