Size and Shape
These are large, long-bodied ducks with thin, pointed wings. Their bills are straight and narrow, unlike the wide, flat bill of a “typical” duck. Females have shaggy crests on the backs of their heads.
Color Pattern
Adult males are crisply patterned with gleaming white bodies and dark, iridescent-green heads for most of the year. The back is black and the bill red. Females and immatures are gray-bodied with a white chest and rusty-cinnamon heads. From late summer to mid-autumn, males wear a nonbreeding plumage that looks very similar to female plumage. In flight, both sexes show large white patches on the upperwings (larger in adult males).
Behavior
Common Mergansers dive underwater to catch fish. Mergansers nest in tree cavities high above the ground. After the chicks leave the nest in summer, the female stays with them as they grow up while males gather in flocks. In winter, mergansers form large flocks on inland reservoirs and rivers. They stay in these tight flocks to feed and court during the cold months. In migration and winter, they mix with other fish-eating, diving ducks.
Common Merganser
Image provided by IBird