Feeding Behavior

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.

Eggs

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.

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.

Diet

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 pondweeds, wild celery, sedges, grasses, and others; also insects and crustaceans.

Nesting

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 a 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.