During the winter 2011 – 2012 Vermont experienced an irruption migration (a sudden upsurge in a specific population) of Snowy Owls (Nyctea scandiaca) which heightened interest in these hardy raptors from both casual and dedicated birders, and it looks like it is happening again! New data fill the Snowy Owl eBird page with details of recent sightings around Burlington, Addison, and towns to the west. Pictures and stories are being shared on bird listservs, Facebook postings, and over coffee with a friend.
Historically, Snowy Owls are known migrants to the southern portions of the Canadian Territories and northern half of the U. S. in winter. Summer’s breeding and nesting season, however, is spent in the circumpolar regions of Europe, Scandinavia, and Greenland where the arctic tundra offers only a barren grassland landscape. Snowy Owls primarily consume lemmings which depend on Arctic grasses and sedges for nesting sites. When vegetation is insufficient, Snowy Owl populations are significantly affected too. Therefore, Snowy Owls are essentially nomadic, breeding where and when prey is abundant.
During an October 4, 2013 talk by noted owl expert Denver Holt, of Montana’s Owl Research Institute, he vividly painted a picture of the Snowy Owl’s strength and determination in not only raising offspring in a demanding habitat but simply surviving its harsh austerity.
Specializing in owl research for the last twenty years, Mr. Holt has spent many summers in Barrow, Alaska trekking across miles of tundra in order to observe and document Snowy Owl breeding pairs and their behavior. Males in breeding plumage are brilliantly white. Their larger mates are easily recognizable with black barring on their breast feathers and primary flight feathers. Largely diurnal, the owls gaze with piercing golden eyes out across the flat lands, wary of two-legged interlopers and watchful for lemmings (Snowy Owls may individually consume as many as 1,600 in one year). Nesting sites are typically raised hummocks of arctic grasses that have been scooped out at the top to create depressions, often plucked of moss and lichens to reveal the peat layer beneath. The white, slightly elongated eggs are laid every two days over the course of ten days. Male Snowy Owls exhibit territorial hooting displays and can produce a variety of calls, such as barking, when agitated by perceived invaders near the nest. Females vocalize with a whistling sound or a mewing call before and after the male Snowy Owl feeds her, or as part of her distraction display. Both male and female Snowy Owls hiss at perceived threats soon after their chicks have hatched. Chicks produce chirping calls but cannot hiss until they are several weeks old.
The Holt research team’s most recent results in studying the breeding ecology of Snowy Owls indicated that Snowy Owl nests have increased in number as has the tally of non-breeding adults. Care is taken to record the numbers of lemmings in a given year and study as well. A correlation between lemming numbers and Snowy Owl population fluctuations has been suggested from analysis of the data over the two decades of collection. This information is significant enough to encourage Mr. Holt to advocate for monitoring the effects of Arctic climate change, through its effect on the Arctic grasses, sedges, and forbs that lemmings consequently consume, and based on the population numbers of the predatory Snowy Owl and its prey, the lemming.
As stated, Mr. Holt has a long tradition of working with student researchers and others in revisiting Snowy Owl breeding grounds to update information on the behavior and population statistics of this magnificent species.
While the task may be considered both personally and scientifically rewarding, the journey is demanding for each individual. The daily trek to a nesting site may involve a 15-20 mile hike with equipment in hand. In order to complete its objectives, the research crew must approach the nest and chicks cautiously yet deliberately. Mr. Holt described the fearsome power and speed employed by male Snowy Owls in striking at interlopers too close to their nests and chicks. Apparently, his Patagonia expedition-wear was fully tested as a protective covering: duct tape marks the spots where the owls’ well-aimed talons met their marks on his parka.
Denver Holt spoke about Snowy Owls as a fundraiser for the Birds of Vermont Museum, who suffered extensive damage this summer due to a flash flood. In addition to wowing the audience with his knowledge, his enthusiasm, and his dedication, he wowed the staff and the Museum’s Board with an amazing offer. Anyone who donates a significant amount to assist in the building of the Museum’s bridge will be able to join Denver Holt in the field. The lucky participant can either join the research team in Barrows Alaska to assist with the snowy owl study, or with one of his many other projects in Montana. Please contact the Museum for more details!
This article also appeared in the December 2013 issue of the Vermont Great Outdoors Magazine
Allison Gergely, Museum Educator, Birds of Vermont Museum