The Black Scoter remains one of North America's least known waterfowl, owing partly to its scattered breeding distribution in remote northern Quebec and Alaska and partly to the perceived lack of interest in this species by hunters. Since the early 1980s, however, the breeding, wintering, and molting distributions of this scoter have been defined more precisely. The center of its eastern breeding population lies in the lake country of northern Quebec, that of its western breeding population in the extensive coastal wetlands of western and northern Alaska. Major wintering areas include the coastal waters of Alaska, British Columbia, and Washington State in the west and those of Maine, Massachusetts, and Rhode Island in the east. Key (known) molting sites are James Bay, Canada; the bays of the Alaska Peninsula; and coastal areas of the western Canadian Arctic.
Adult male Black Scoters are easily identified by a yellow protuberance on the bill and by their entirely dark black plumage, adult females by their dark brown plumage with contrasting dark cap and light cheeks. This species is among the most vocal of waterfowl. Groups of this scoter can often be located by the constant mellow, plaintive whistling sound of the males. Aquatic insects in summer and mollusks in winter typify the species' diet. In winter, birds feed mostly in monospecific flocks in shallow coastal waters. Large concentrations are found at molting sites where groups of several thousand males have been recorded.
The breeding ecology of this species remains poorly known, based on only a few initial studies. Only a few nests have been found to date, and most data on breeding come from studies of its European congener, the Common Scoter (Melanitta nigra) of Eurasia. Reproductive success of this species can vary significantly between years, making adult survival crucial to its population dynamics; thus, this species is particularly sensitive to hunting mortality. Much remains to be learned about this elusive species.