The common merganser or goosander is a large sea duck of rivers and lakes in forested areas of Europe, Asia, and North America. The common merganser eats mainly fish. It nests in holes in trees. The name "common merganser" is used in North America, while "goosander" is used in Eurasia.
Region
Holarctic
Typical Environment
Breeds across forested rivers and lakes of northern North America, Europe, and Asia, favoring clear water for visual hunting. During winter it shifts to larger unfrozen lakes, wide rivers, and sheltered coastal bays. It selects habitats with abundant fish and nearby nesting cavities, including mature woodlands or cliffs with crevices. Outside the breeding season it is more tolerant of open waters and human-altered shorelines.
Altitude Range
Sea level to 3000 m
Climate Zone
Temperate
Ease of Keeping
Beginner friendly: 1/5
Also called the goosander in Eurasia, the common merganser is a large sawbill duck adapted for catching fish with its serrated bill. It nests in tree cavities or nest boxes near water, and ducklings famously leap from the nest to follow the female to water soon after hatching. In winter it often forms flocks on unfrozen lakes and rivers or sheltered coastal waters.
Temperament
wary but gregarious in winter
Flight Pattern
strong flier with fast, direct flight and audible wing whistle
Social Behavior
Often nests singly or in loose colonies where cavities are available; females lead broods to water shortly after hatching. In winter it gathers in flocks, sometimes forming mixed-species groups with other diving ducks. Females may form creches, combining broods for collective defense.
Migratory Pattern
Partial migrant
Song Description
Generally quiet; males give low croaks and grunts during courtship. Females produce harsher rasping calls, and wingbeats often create a distinctive whistling in flight.
Plumage
Sleek, smooth plumage with strong sexual dimorphism; males are crisp white with a dark iridescent green head and black back, females are gray-bodied with a rufous head and shaggy crest.
Diet
Primarily piscivorous, taking small to medium fish captured by underwater pursuit. It also consumes aquatic insects, crustaceans, and occasionally amphibians, especially in the breeding season. Serrated bills and strong, narrow heads help grip slippery prey, and it hunts by sight in clear water.
Preferred Environment
Feeds in clear rivers, large lakes, and sheltered coastal inlets with good underwater visibility. Often works along shorelines, riffles, and drop-offs where fish concentrate.
