The long, narrow bill with serrated edges readily distinguishes mergansers from all other ducks. Common mergansers are among the largest ducks, but are less stocky than eiders and goldeneyes. In flight, they appear more elongated than other ducks, flying in trailing lines close to the water surface.
Male common mergansers have a greenish-black crested head and upper neck. The lower neck, breast, and underparts are creamy-white with a variable pink wash. They have black backs and upperwing coverts with white scapulars. The bill is red with a blackish culmen and nail. The legs and feet are deep red.
Female common mergansers have a tufted red-brown head that is clearly defined from the lower neck by a clear whitish chin. The back and sides are silver-gray and the breast and belly are white. The bill is red with a blackish culmen and nail. The legs and feet are deep red.
Common mergansers nest in tree cavities, nest boxes, cliff crevices, and on the ground generally near clear water rivers in forested regions and mountainous terrain. They feed by diving underwater in marine and freshwater habitats.
This duck has a wide distribution in boreal and temperate regions of Eurasia and North America. It has also isolated populations in the mountainous regions of the Alps, the Caucasus and Tibet. Two populations inhabit or visit the European Union. One comprises the birds of northern and north-western Europe, wintering mainly in the Baltic Sea and around the North Sea. It amounts to about 200000 individuals, and seems stable. The birds of the British Isles are sedentary. They amount to about 5000-8000 individuals and increased during the last decades. The population of Central Europe (France, Germany) amounts to 3000 individuals. It is also sedentary and seems to be slightly increasing. A very small population is breeding in the Balkan Peninsula. It is estimated at not more than 11-32 breeding pairs, and its trends are unknown
Common mergansers eat mainly fishes, amphibians, crustaceans, mollusks, and other invertebrates obtained by diving underwater in marine and freshwater habitats
This species has a large range, with an estimated global Extent of Occurrence of 10,000,000 km². It has a large global population estimated to be 450,000-1,400,000 individuals (Wetlands International 2002). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern. [conservation status from birdlife.org]
Common mergansers breed from Alaska, the southern Yukon, Labrador, and Newfoundland south to central California, Arizona, New Mexico, southern Chihuahua, and, east of the Rockies, to Minnesota, Michigan, New York, New England, and Nova Scotia. Common mergansers nest in tree cavities, nest boxes, cliff crevices, and on the ground generally near clear water rivers in forested regions and mountainous terrain. Female common mergansers lay an average of 9 to 12 eggs.
Migratory and partially migratory. No evidence that any Icelandic breeders emigrate. Similarly, British breeders almost entirely resident, moving short distances (mainly within 150 km) from breeding waters to lakes and sheltered estuaries. No evidence that breeders of southernmost Scandinavia, north Germany, and Poland move further than western Baltic, but those breeding central and northern Scandinavia, Finland, Baltic States, and Russia east to Pechora migrate west to Baltic and beyond to Netherlands and Britain, in smaller numbers to west France and north Spain.
In late August and early September, moulting and breeding waters often deserted as flocks build up on estuaries and shallow parts of some inland lakes. Mass departures not until advent of freezing; thus major movements through Russia and Baltic October and early November. Early arrivals in North Sea countries late October and early November, but no large numbers until December, while numbers build up on Black Sea and Sea of Azov from mid-October to mid-December. Return migration from early March and, apart from stragglers, non-breeding range vacated by mid-April.
- spanwidth min.: 78 cm
- spanwidth max.: 94 cm
- size min.: 58 cm
- size max.: 68 cm
- incubation min.: 30 days
- incubation max.: 32 days
- fledging min.: 60 days
- fledging max.: 70 days
- broods 1
- eggs min.: 5
- eggs max.: 15
- Conservation Status