Medium-sized duck, dives for invertebrates. Often in flocks and pairs on variety of water bodies. Head shape is best way to separate from nearly identical Greater Scaup; note peak near rear of crown. Also similar to Ring-necked Duck but grayer back and whiter flanks. Breeding males have dark head with green or purple sheen and bright white sides with some faint barring. Females are darker brown than Ring-necked Duck.