The Black Scoter is divided into two subspecies. In the form found in Europe, the "Common Scoter," the male has a larger swollen knob at the base of the upper bill that is black on the sides with a yellow stripe on top, not entirely yellow.
The Black Scoter occasionally does a "Wing-flap" display while swimming, flapping its wings with its body held up out of the water. Unlike other scoters, it almost always punctuates a Wing-flap with a characteristic downward thrust of head, as if its neck were momentarily broken. Surf and White-winged scoters keep their heads and bills pointing more or less above the horizontal throughout a Wing-flap.
The Black Scoter is among the most vocal of waterfowl. Groups of Black Scoters often can be located by the constant mellow, plaintive whistling sound of the males.
The oldest recorded Black Scoter was a male, at least 10 years, 6 months old.