Like ghosts from the Arctic, snowy owls have descended from the far north this winter. They’re showing up in fields, along highways and even in a few backyards. These migrations southward from the arctic tundra are a birdwatcher’s dream. And like dreams themselves, they are neither predictable nor fully understood.
The classic theory held by ornithologists to explain the irregular migrations of snowy owls to this region has always centered on lemmings, a favorite food of the owls. 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 head southward in search of food. Intensive research now shows this may not be the case.
Norm Smith, director of Massachusetts Audubon’s Blue Hills Trailside Museum, has been monitoring snowy owls for more than 25 years at Boston Logan Airport. The broad stretches of land around airport runways tend to look like tundra and become a winter Mecca for wayward owls. But Smith and others have discovered a twist to the old migration theory. We actually see the most snowy owls in the New England during lemming population boom in the arctic, not after the lemming population has plunged.
It takes lots of meat to raise a snowy owlet. Researchers have estimated that a pair of snowy owls and a brood of nine owlets eat 1,900 to 2,600 lemmings during the breeding season from May to September. That’s about 325 pounds of rodent meat. Lots of lemmings allow for lots of owls, and when younger owls start outgrowing their natal territory, the adults chase them away. They have to find somewhere else to dine, which often means flying southward.
Smith and other ornithologists can count the number of young owls each winter. That’s because young snowy owls have plumage that is slightly different than their parents. Young females have extensive dark lines throughout their feathers giving them a black and white zebra pattern. While young males have a pure white bib under their chin and the back of their head is entirely white.
With small transmitters secured on the backs of owls, ornithologists 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 telling hat allows telling the birds’ exact locations. 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 the April 5, and after crossing the Connecticut River, was in northwest Vermont by the 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 north shore.
Snowy owls are capable of taking even larger birds. Smith reports he once witnessed a snowy owl take flight from a lamppost near the airport and accelerate toward a great blue heron that had just lumbered into flight along the shoreline. Much to Smith’s surprise, the owl punched the bird to the ground to make for one very big meal.
Humans have admired snowy owls for centuries. Their images have been found in ancient cave paintings in Europe. And this year, whether gracefully sitting in a harvested cornfield in Brattleboro, Vermont or a along the runway of Boston Logan Airport, surprised birders always stare at them in awe. Whether their dinning on Vermont meadow voles or arctic lemmings, this magnificent bird reminds us that these seemingly far off landscapes are bound together through the quiet flights of the Snowy Owl on their search for food.