By Tom Warren —
This large, northern circumpolar owl breeds in the Arctic tundra from tree line to the edge of the polar seas. It is highly nomadic and, in some years, migrates to the U.S. in large numbers due to a lack of its main prey, lemmings (a small rodent). This is one of those years with hundreds already being reported, some as near as Mt. Watatic (near Rindge) and Brattleboro, VT. You can see this distribution by searching “Got Snowies?” published by eBird. 
Unlike many other owls, the Snowy Owl is diurnal and hunts in all weather during winter. In years of great prey abundance, female snowy owls lay as many as a dozen eggs. Adults are estimated to eat as many as 1,600 lemmings annually. In years of few lemmings, females do not raise a family, somehow knowing there will be no food for their young owlets.
Adult males are smaller and paler than females. They are very aggressive in defense of their young, often striking humans and wolves at their nests on the Arctic tundra. Young owls are heavily marked with black and brown streaks.
They usually appear in New England at coastal locations that mirror the Arctic tundra where they breed. Portsmouth (NH), Salisbury Beach, Duxbury Beach and Plum Island (all MA) are the best locations to see these owls in winter. They appear in four-year cycles following a crash in the lemming population.
Snowy Owls have very thick plumage and their legs are heavily feathered to protect them from the cold.
In a research project, a Snowy Owl was subjected to temperatures of 135 degrees below zero, colder than temperatures ever recorded in Antarctica. The bird survived these lethal temperatures with no ill effects. At these temperatures the owl burned calories at five times its normal rate.
Man was the primary enemy of the Snowy Owl. In the early 1900s, one thousand Snowy Owls were shot annually in Ontario. Today, they are protected and winter mortality is usually caused by collisions with cars, utility wires and aircraft. A Snowy Owl, the first ever recorded in Hawaii, was shot recently at the Honolulu Airport because it posed a threat to aircraft.
Your children and grandchildren will have a better understanding of this beautiful winter owl because of the Harry Potter movies in which this owl stars.
Tom Warren is a Trustee of the Harris Center for Conservation Education and New Hampshire Audubon.