March 1, 2012
By: Elizabeth Decelles
Snowy owls (Nyctea scandiaca) are known for their striking white plumage, bright yellow eyes, and black beaks. They are a nomadic creature typically found in the arctic tundra, and travel wherever abundant prey resources exist. Snowy owls mainly subsist on a diet composed of lemmings and voles. Unlike other owls, they are diurnal raptors and forage during daylight hours. This year, they have made a dramatic invasion much further south than their typical winter limits and have been spotted as far south as Oklahoma and Hawaii. “Already we can see that this year is one of the biggest irruption years ever for snowy owl,” says Chris Wood, a Cornell University ornithologist and project leader for Cornell and Audubon’s eBird, an online database of avian observations.
Historic snowy owl irruptions south, such as those in 1945-46 and 1966-67, have been attributed to the cyclic crash of lemming populations further north. However, this is unlikely the cause of the current irruption, writes Sam Galick, eBird data reviewer:
Arctic researchers suggest an interesting twist, however, that the lemmings this year were at historical population highs allowing for a very successful breeding season for Arctic raptors, including Snowy Owls. The resulting population boom causes overcrowding and competition at typical wintering grounds pushing inexperienced birds farther south into the Lower 48. In years when Snowy Owls irrupt, watch for Rough-legged Hawks too—their similar prey choices could create similar patterns of occurrence.
A majority of these owls are young, inexperienced birds. They have traveled excessive distances to find prey, and arrive stressed and hungry. Spotting a snowy owl in the wild is thrilling, but ornithologists encourage birders to enjoy them from a distance, and not to pursue them for photographs or a better view.