White-winged Scoters mainly breed in boreal forest from Alaska to Western Canada and are less common east towards the Hudson Bay and south towards the Canadian Prairies. They winter further south in temperate zones, on the Great Lakes, the coasts of the northern United States and the southern coasts of Canada. They have occurred as a vagrant in Europe, including Scotland, Iceland, Norway and Ireland. The white-winged scoter is one of three North American scoter species and the largest species of scoter. In freshwater, this species primarily feeds on crustaceans and insects; while in saltwater areas, it feeds on mollusks and crustaceans. The favorite foods are amphipods in freshwater, and rock clams, Atlantic razor clams and Arctic wedge clams. They are monogamous and form pairs in late summer, suggesting long-term pair bonds. The male is all black, except for white around the eye and a white speculum; the female has a much larger patch of white under the eye and a black bill.