Often gathers by the thousands on lakes or bays in the winter. About the size of Greater Scaup, but slightly larger than Lesser Scaup and Ring-necked Duck—this can be helpful when they are together in mixed flocks. Best separated from Canvasback by head and bill shape and male’s darker gray body. Breeds on marshy freshwater ponds and lakes; winters in flocks on any large body of water, often mixed with other diving ducks. Dives frequently to reach submerged aquatic vegetation.