Snowy Owls Are Here Again, But Why?

Snowy Owls Are Here Again, But Why?

Illustration by Adelaide Tyrol

Like ghosts from the Arctic, snowy owls have descended on New England this winter. They’re showing up in fields, along highways and in some backyards. These migrations from the arctic tundra are a birdwatcher’s dream. And like dreams themselves, they are not fully understood – though scientists may be making some headway

The classic theory about the migrations of snowy owls to this region has centered on a favorite food of the owls: lemmings. These small rodents undergo population booms and busts. About every four years lemmings become incredibly abundant. Many scientists believed that after the lemming populations eventually crashed, snowy owls would fly south in search of other prey.  Research now shows this may not be the case.

Norm Smith, director of Massachusetts Audubon’s Blue Hills Trailside Museum in Milton, has been monitoring snowy owls for more than 25 years at Boston’s Logan Airport. The broad stretches of land around airport runways can look like tundra and a winter Mecca to wayward owls. But Smith and others have discovered a twist to the old migration theory. We actually see the most snowy owls in New England during a lemming boom in the arctic, not after a bust.

Lots of meat is needed to raise a snowy owlet. Researchers estimate a pair of snowy owls and a brood of nine owlets (a female will lay five to 14 eggs) will eat as many as 2,600 lemmings during the May-to-September breeding season. That’s about 325 pounds of rodent meat. Lots of lemmings allow for lots of owls; but even though the food supply for the time being may be ample, adult owls begin chasing away younger ones after they can manage on their own. And many of the young ones head south. 

Studies on northern Quebec’s tundra by Laval University doctoral student Jean-Francois Therrien, recently presented in Quebec City at an ‘Arctic Change Conference,’ seem to corroborate Smith’s observations. “We had the largest abundance of lemmings in many years in our study area this past summer,” Therrien reported in a press release. “The owls had no problems raising young, so we were informally predicting a strong outward movement of young owls this winter.” With record numbers of snowy owls reported across many parts of New England this winter, his prediction was on the mark.

(Smith and other ornithologists find it relatively easy to count the number of young owls each winter. That’s because young snowy owls are not white or mostly white like their parents, but are heavily barred, zebra-like, with dark brown coloration.)

With small transmitters secured on the backs of owls, Smith and Therrien also have been able to witness some amazing flights by these owls. The transmitters periodically send a location signal to a satellite, which sends back information on the birds’ exact location. Smith has discovered that snowy owls that winter in Massachusetts spend summers in northern Quebec and Baffin Island, sometimes above the Arctic Circle. Some take a northwest route through New Hampshire and Vermont on their spring trip back to the tundra. 

Take the year-old female that left coastal Massachusetts on April 1, 2005. She arrived east of Lake Winnipesaukee in New Hampshire on April 5, and after crossing the Connecticut River, was in northwest Vermont by April 8. On May 22 her signal came from the center of Hudson Bay. After perhaps hunting on the ice flows in the bay, she made landfall five days later on the bay’s northern shores.

Therrien may be on the path to understanding what these owls do after they continue on to the Arctic Sea. “Six of the adult females that we followed in a satellite study spent most of last winter far out on the Arctic sea ice,” he said. Snowy owls are powerful predators, and Therrien thinks the owls feed on sea ducks, such as the common eider. 

Snowy owls are capable of killing even larger birds. Smith reported once witnessing a snowy owl take flight from a lamppost near Logan and accelerate toward a great blue heron that had just lumbered into flight along the Boston Harbor shoreline. Much to Smith’s surprise, the owl punched the bird to the ground to make for one very big meal. A sitting duck would be no match for this predator.

Humans have admired snowy owls for centuries. Their images have been found in ancient cave paintings in Europe. And this year, whether the owls are munching a vole in some New Hampshire meadow or gracefully perching on a weather vane in Whiting, Vermont, excited birders stare at them in awe. These magnificent birds, appearing in our midst every few years, remind us that two very different landscapes are bound together through their quiet flights. 

Kent McFarland is a biologist with the Vermont Center for Eco Studies.

 
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