Snowy owl invasion is underway
Nothing gets birders more excited than widespread reports of unusual birds. They jump in their cars, drive hundreds of miles, and hope to spot a "life bird." Sometimes they are successful; sometimes they are not. It's all part of the thrill of birding.
Right now much of the northern United States is being invaded by snowy owls. From Minnesota to the East Coast and as far south as West Virginia, birding hot lines have been humming with reports of dozens of snowy owls. Every day this week I've seen new reports of snowy owls.
So far most reports are coming from the Great Lakes states and the Northeast. Last weekend one even showed up in Bermuda. In 2011 a similar invasion saw most of the reports originate in western states.
Featured prominently in J.K. Rowling's "Harry Potter" books and movies, snowy owls are well known among the general public. Birders, however, have long held these occasional visitors from the north in high regard. It can take decades to check this species off on a life list. I saw my one and only snowy owl in Oklahoma on the prairie in the early 1980s.
Normally snowy owls live on the tundra of northern Canada and Alaska far from most human observers. When lemming populations are high, females lay as many as 13 eggs. When lemming numbers are low, they lay as few as 3 eggs, or they may forego nesting entirely. Regardless of nesting success, however, every three to five years at least some wander south, presumably in search of food.
Snowy owls eat lemmings, voles, and other small rodents, and periodically these small mammal populations crash. When that happens, the owls can either head south to find food or starve. So they wander south until they find new food sources, which can include a variety of birds and small mammals.
Though a primary predator of lemmings and voles, snowy owls may actually help rodent populations. When rodents are plentiful, owls eat them and their droppings fertilize the barren tundra landscape and stimulate the limited plant growth. This in turn provides habitat for the rodents. But when snowfall is limited, rodents become easy prey and this contributes to periodic population crashes. So perhaps the snowy owls themselves help trigger the population crashes that send them in search of better winter food supplies.
Whatever the cause, snowy owl irruptions into temperate zones delight birders. Snowy owls are difficult to miss. Unlike most owls, they are active by day and thus easily seen. Furthermore, they prefer open habitat -- pastures, hayfields, airports, golf courses, beaches, cemeteries, etc. -- and this also makes them easy to see. Often they perch conspicuously on large rocks, fence posts, power line poles, and even the roofs of buildings.
Snowy owls stand about two feet tall, have a wingspan of more than four feet, and weigh about four pounds. Older males are mostly white; first year birds are heavily marked with black bars, and adult females show some black barring. Often during these periodic southward irruptions, many birds are juveniles. This suggests that when food becomes limiting, young birds are the first ones to leave the far north.
To learn if any snowy owls have been seen near you, call a local nature center or wild bird store. Or search online for "snowy owls near ______" and fill in your location.
If you get lucky and find a snowy owl, keep your distance. These birds are stressed, hungry, and have traveled a long distance. If you get too close and spook them, you only compound the stress.
Sometimes when searching intently for a special bird, eyes can deceive. Beware that sometimes all is not as it seems. Every birder has been duped a time of two (or 20) into thinking a prominent rock, stick, or plastic bag is a bird. I've got several "leaf birds" on my life list. There's no shame in being fooled. To see what I mean, visit this website by Matt Webb: http://thatsnotasnowyowl.tumblr.com.
For continuing coverage of the snowy owl invasion, visit www.ebird.net.