Snowy owls breed in the Arctic, where they feed primarily on lemmings. Since the lemming population tends to crash every four years or so, snowy owls generally appear across the northern half of the U.S. in those winters. During these irruptions, the owls feed on a variety of small mammals, waterfowl and sea birds.
This winter, a spectacular invasion of snowy owls is occurring in eastern North America; while concentrated in southeastern Canada, New England and the Great Lakes region, the beautiful raptors have been spotted southward, from Missouri and Arkansas to North Carolina and, of all places, Bermuda. Most of the birds are heavily marked with black feather edging, indicating that they are young birds, having fledged this past summer. This observation suggests that the invasion is primarily due to an overpopulation of snowy owls in the eastern Arctic rather than to a crash in the lemming population.
While the specific cause for this invasion is not yet certain, it has garnered a great deal of attention among birders throughout the eastern U.S. Whether global warming is beginning to have some affect on both breeding success and irruptive behavior is an intriguing consideration. Indeed, the ongoing disruption of the Arctic ecosystem will have a significant impact on more southern ecosystems as well; the opportunity to see more snowy owls does not balance the many negative effects that will come our way.
