Friday, March 7, 2014
A suite of birds resides year-round on the Arctic tundra or on the taiga, the habitat of sparse trees just south of the treeless tundra. These birds include great gray owls, snowy owls and common redpolls.
A snowy owl takes flight at Reid State Park in Georgetown, one of many sightings this winter.
Photo by Doug Hitchcox
If food is in sufficient quantity, these hardy birds can survive the deep cold of these northern habitats. However, food availability varies from year to year. Common redpolls depend heavily on the seeds of birches. When birches fail to have an abundant seed set, the redpolls move southward to find food. In some years, we Mainers are graced with abundant redpolls at our feeders.
Snowy owls feed primarily on lemmings in their arctic tundra habitat. Like many rodents, lemmings undergo dramatic shifts in abundance from year to year.
One snowy owl may eat 1,600 lemmings in a year. When lemming populations crash, some snowy owls move southward to find food. Apparently, the lemming populations on the tundra are poor this winter because a major invasion of the lower 48 states by these owls is occurring.
I know of at least 30 sightings of snowy owls in Maine this winter, ranging from northern Aroostook County all the way south to coastal York County. A snowy owl has been regularly seen at Nubble Light in York.
Most sightings have been made along the coast. However, this apparent preference for the coast may be more of a function of the density of birders rather than the density of the owl population. Regardless, in most years we see just a few snowy owls in the state, or sometimes none.
A dynamic map of the snowy owl invasion is available on the eBird site (tinyurl.com/6wdc9qa).
The map shows that snowy owls have been sighted in the southern portions of all the Canadian provinces.
All of the northern tier of American states have some snowy owl sightings, although more birds have been found in the Midwestern states eastward to Maine.
Birds have been found as far south as Missouri and Oklahoma, absolutely delighting birders there, where snowy owls are truly rare. Amazingly, a snowy Owl appeared at an airport in Hawaii in January. Sadly, airport officials shot the owls, fearing the owl would interfere with the planes.
Snowy owls are strikingly beautiful birds. They stand about 2 feet tall with a wingspan of nearly 5 feet. As the name suggests, the birds are mostly white. Most snowy owls show some blackish-brown streaking and spotting on their backs and lower breast. First-year females show the most dark streaking, with the barring extending to the crown and the upper breast. Adult females and first-year males show less dramatic dark coloration and are difficult to tell apart in the field. Adult males are paler yet, often nearly immaculate white. Males are distinctly smaller than females.
Often exposed to cold temperatures, snowy owls have legs feathered all the way to the claws of the toes. Most of the bill is concealed by feathers, as well.
A snowy owl is difficult to misidentify. Snowy owls are the only white owl found in North America. The only possible confusing species is the sub-arctic race of the great horned owl. These birds are quite pale with brown streaking, but the prominent ear tufts easily distinguish these great horned owls from snowies.
The distinctive appearance of snowy owls makes them easy to recognize in primitive art. This species is probably the oldest species of bird that can be identified in prehistoric cave art.
The preponderance of invading snowy owls are young birds, probably less skilled in finding food than adults. The eyes of snowy owls are yellow. We think of owls as nocturnal predators. However, snowy owls hunt during the day for rodents.
Recent DNA studies indicate that snowy owls are closely related to great horned owls, great gray owls and other owls in the genus Bubo.
Herb Wilson teaches ornithology and other biology courses at Colby College. He welcomes reader comments and questions at: