Bird of the Month: Common Merganser
By Hugh Jennings
PC: Mick Thompson (Common Merganser)
Scientific Name: Mergus merganser
Length 25 in
Wingspan 34 in
Weight: 3.4 lb (1530 g)
AOU Band code COME
The Common Merganser (COME) is about 25” long with 34” wingspan and weighs 3.4 lb (1530 g). The genus name Mergus is Latin for diver. The species name merganser is from Latin mergere meaning to dip, plunge, and anser meaning goose. It is called Common because it may be seen more often than other members of its genus.
This bird has a long, slender, hook-tipped red bill. The male has a dark green head with a white breast and flank, and a dark back. The female is gray with a red-crested head that is sharply separated from a white neck and breast. For immature COMEs, the female is like the adult while the male looks like the female at first, but then gradually begins to develop the adult male plumage by first spring. The British call this bird the “Goosander”.
It is a fish-eating duck that is common on freshwater lakes across the United States and is found year-round on the coasts of Canada. It is only inland in Canada during the nesting season. It prefers freshwater, but can also be found on clear salt-water bodies. In Washington state this duck is a year-round resident. It is common at low elevations in winter and during breeding at low to medium elevations on shallow, clear rivers and lakes in forested country. It avoids dense marshes and muddy waters. The COME diet is a large variety of fish, but it will also eat mussels, shrimp and salamanders. Adult males can swallow fish more than a foot long. Young feed mostly on aquatic insects. This duck forages singly or in a flock by diving and swimming underwater, stroking with both feet in unison. Most food is found by sight by swimming along the surface, dipping its head underwater until prey is seen, then it diving in pursuit.
Courtship displays of the male involve swimming very rapidly in circles near the female, then suddenly stretching it neck upward, pointing its bill straight up, and giving a soft call. Otherwise it is usually silent. Nesting is in a natural tree cavity or a large woodpecker hole, usually near water. They also nest in rock crevices, holes under tree roots and in undercut banks, or in nest boxes. Nest material is wood chips or weeds with a lining of down. There are usually 8-11 buff-colored eggs, sometimes 6-13. Females will often lay eggs in each other’s nests. Only the female incubates the eggs, usually for 30-35 days before the eggs hatch.
The young may stay in the nest for a day or more, then climb to the cavity entrance and jump to the ground. The female cares for the young for several weeks, but the young usually feed themselves and they may survive even if abandoned. The young are able to fly about 60-75 days after hatching. The COME migrates mainly in small groups from Canada to the United States. The adult males seem to winter farther north than the females and young. Migration is usually late in fall and early in spring.