Fairly common though often localized n. breeder. Often forms large flocks in winter in deepwater coastal bays, estuaries, and sometimes on the ocean. Often mixes with very similar LESC. ID: Sometimes differences from LESC are obvious and other times a real head-scratcher (see LESC for comparison). A large diving duck with broad head and evenly domed crown, thick neck and bulging cheeks. Broad bill flared at tip with black typically extending off the nail onto leading edge of bill (usually restricted to nail in LESC). Sometimes with other diving ducks; comparing size is a good id starter. Females appear fairly uniform brown with variable amounts of gray mixed in and well-defined white around base of bill. Worn birds (late winter/summer) often show a white cheek patch (more so than LESC). Imms as adult female but initially darker brown iris and generally more uniform brown. Bill shows less white at base. Male’s iridescent green head often appears black, but almost never purple. Eclipse/imm male initially as female; usually finish molt into bright plumage by late fall (LESC later).