Flocks of these large sea ducks enliven northern coastlines. Males are white and black with a soft suffusion of green on the nape. Immature males are variable and messy-looking with patches of black and white. Females vary from rich rufous-brown to cold grayish, always with extensive black barring covering body and wings. Slight variation in bill shape and color across subspecies, especially obvious on males; Pacific birds have brightest orange bills, most others have greenish bills. Dives to feed on mollusks and other crustaceans. In late summer, look for flocks of females with dozens of ducklings; broods often join together. Compare females with other eider species, and note details of bill and head shape.