Very similar to Lesser Scaup in plumage; best separated by careful study of head and bill shape. Males have black breast, medium gray back, white sides, and yellow eye. Head appears black with a greenish sheen in good lighting, never purplish. Females are brown overall, grayer on body in winter, with white patch at base of bill and yellow eye. To distinguish from Lesser Scaup, note smoothly rounded head without tall peak and puffier cheeks. Also larger, broader bill and more extensive white stripe on wing in flight. Tends to prefer saltwater bays and coves, but also found in freshwater. Often in flocks with Lesser Scaup, Redhead or other Aythya ducks.
See: Merlin ID by Cornell Lab
Ducks and Geese
Songs & Calls:
Usually silent; discordant croaking calls on breeding grounds.
Breeds in Alaska and northern Canada east to Hudson Bay and occasionally in Maritime Provinces. Winters mainly along Pacific, Gulf, and Atlantic coasts. Also in Eurasia.
Migrates in flocks. Birds from Alaska may winter on either Pacific or Atlantic coast; banding records indicate that the same individual may go to opposite coasts in different winters, probably as a result of joining different flocks.
Lakes, rivers, salt bays, estuaries. In summer on lakes and bogs in semi-open country near northern limits of boreal forest, and out onto tundra. In winter mainly on coastal bays, lagoons, estuaries; some on lakes inland. Overlaps with Lesser Scaup at all seasons, but in winter the Greater tends to be on more open bays, more exposed situations.
Forages by diving and swimming underwater; large food items brought to surface to be eaten. Occasionally forages by dabbling or up-ending in shallow water. May feed at any time of day, or at night, with timing affected by tides in coastal regions.
Mostly mollusks and plant material. Diet in winter is mainly mussels, clams, oysters, snails, and other mollusks. In summer (and perhaps in winter on fresh water) consumes plants including pond weeds, wild celery, sedges, grasses. and others; also insects and crustaceans.
Pair formation occurs mostly in late winter and early spring. Several males may court one female. Display elements of the males include throwing the head back sharply while giving a soft call; exaggerated bowing movements, with bill tip lowered to water and then raised high; flicking wings and tail while giving soft whistled notes. Nest site usually very close to water on island, shoreline, or mats of floating vegetation. Nest is shallow depression, lined with dead plant material and with down. Female chooses nest site and builds nest. Several nests may be close together in loose colony.
7-9 sometimes 5-11. Olive buff. Incubation is by female only, 24-28 days. Young: female leads young to water shortly after hatching; 2 or more broods may join, tended by 1 or more females. Young feed themselves, are capable of flight 40-45 days after hatching.