With its black plumage and bright orange base to the bill the male Black Scoter is unlikely to be confused with any other duck. The orange patch on the bill is visible from considerable distances, even in flight. The dark brown plumage of females and immatures is similar to that found in other female scoters. Note that the Black Scoter has a rounder head and lacks white patches on the face instead having a pale face contrasting with a dark crown. In flight, note the paler undersides to the flight feathers contrasting with the dark wing linings. The round head and dark plumage of the female Black Scoter is somewhat reminiscent of the American Black Duck but the bill of the black duck is greenish, not black.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.