Of the world's 3 species of scoters (White-winged, Surf, and Black scoter), all of which inhabit Holarctic waters, the White-winged Scoter is the largest and best known, in part because its nests are the most accessible. This scoter nests on freshwater lakes and wetlands in the northwestern interior of North America and winters along the Pacific and Atlantic Coasts. Known in Europe as the Velvet Scoter, in reference to the male's rich black plumage, this species (both sexes) has a large stocky body and a prominent white speculum on each wing. Males are distinguished by their black plumage and a hump in the middle of their brightly marked bill, and in both sexes the base of the bill is swollen.
When taking off, the White-winged Scoter runs and flies along the surface of the water for a short distance. Once in the air, its flight is swift and direct, powered by a rapid wing beat. Individuals often fly low over the water in lines referred to as strings, but most of their time is spent loafing or swimming on the surface. They feed almost exclusively by diving, generally taking prey on or near the bottom. Mollusks (especially the blue mussel, Mytilis edulis) and crustaceans are important foods on wintering areas—generally open coastal environments, especially bays and inlets, where food is likely to be most abundant. On its breeding areas, this species favors large wetlands and lakes, either brackish or freshwater sites. Foods on breeding areas include crustaceans (especially the amphipod Hyalella azteca) and insect larvae distributed along or near the bottom.
The White-winged Scoter is serially monogamous: The male leaves his mate soon after she begins laying eggs. Females sometimes nest in high densities on islands but more often appear to nest up to several kilometers from water. Nests are typically hidden beneath dense, thorny vegetation, e.g., gooseberry (Ribes spp.) or rose (Rosa spp.) bushes. Individuals return to the same general area to nest in subsequent years and may even use the same nest bowl. The survival rate of young scoters is low, with most mortality occurring in the first few weeks of life.
Although not generally prized by sport hunters, significant numbers are shot each year, especially along the Atlantic Coast of North America where there is a rich tradition of sea duck hunting. Because of this species' low rate of recruitment and strong philopatry to nesting areas, disturbance during the nesting season and hunting on breeding areas have the potential to eliminate local populations.