Introduction
The Common Merganser, Mergus merganser, is a large diving duck of the sawbill family, Anatidae. Also known as the Goosander in Europe and Asia, it is recognised by its long, narrow, serrated bill, which is adapted for gripping slippery prey. The species occurs across northern North America, Europe and Asia, using clear rivers, lakes and reservoirs with suitable fish populations.
Physical Description
The Common Merganser is a large, long-bodied duck measuring approximately 54–71 cm in length, with a wingspan of about 86 cm. Its long, narrow bill, streamlined shape and pointed wings reflect its specialised diving lifestyle.
Adult males in breeding plumage have a dark, iridescent green head, a bright red bill, a white body and a black back. Females have a grey body, a rusty-cinnamon head with a shaggy crest, and a sharply contrasting white throat and chest. Outside the breeding season, males develop a non-breeding plumage that resembles the female’s colouring.
Juveniles and immature males are generally grey and brown, with less pronounced crests and more extensive pale areas on the face. In flight, both sexes show prominent white patches on the upperwings, although the pattern varies between geographic populations.
The bill has fine serrations along its edges. These saw-like structures help the bird hold fish and other slippery prey underwater.
Range and Habitat
The Common Merganser has a broad circumpolar distribution across North America, Europe and Asia. In North America, it breeds mainly across Alaska, Canada and the northern United States, with many birds moving south during winter. In Europe and Asia, it breeds from northern regions southwards through suitable mountain and temperate habitats, and it is often called the Goosander.
Breeding birds favour clear, fish-rich rivers and lakes bordered by mature woodland. The species nests in tree cavities, including old woodpecker holes and natural hollows, usually close to water. It may also use artificial nest boxes and, less often, cavities in banks, cliffs, hollow logs or buildings.
During migration and winter, Common Mergansers gather on larger lakes, reservoirs and rivers that remain open. They are mainly freshwater birds but may occur in sheltered estuaries and coastal bays, particularly where inland waters are frozen. Local populations may be resident, partially migratory or fully migratory, depending on latitude and winter conditions.
Where to See This Species
Whiskeytown National Recreation Area, California, United States
The National Park Service lists the Common Merganser as a common species at Whiskeytown National Recreation Area. The species is most likely to be found on the park’s large reservoir and associated freshwater shorelines, particularly where there are open stretches of water and suitable fish habitat.
Nearby accommodation: Redding is the main gateway for hotels, motels, guest houses, cabins and camping options in the surrounding area.
Redwood National and State Parks, California, United States
The Common Merganser is documented along streams and riparian areas in Redwood National and State Parks. Redwood Creek, Prairie Creek and Mill Creek are identified as useful areas to search, especially where clear water, rocky margins and overhanging woodland provide suitable habitat.
Nearby accommodation: Crescent City, Klamath and Orick provide practical bases with hotels, guest houses, cabins, campsites and other accommodation.
Denali National Park and Preserve, Alaska, United States
Denali’s official bird list records the Common Merganser as a complete migrant associated with ponds, lakes and wetlands. It is not listed as abundant, so sightings are likely to be occasional, particularly during migration or around suitable open water.
Nearby accommodation: Healy and the park entrance area provide the main accommodation base, including hotels, lodges, cabins, campsites and self-catering options.
Behaviour and Diet
Common Mergansers spend much of their time on the water, where they rest, swim and search for prey. They dive underwater to pursue fish, usually hunting by sight in clear water. Small and medium-sized fish form the main part of the diet, supplemented by aquatic insects, crustaceans, molluscs, amphibians and other aquatic animals when available.
They may forage alone, in small groups or in larger winter flocks. When several birds are feeding together, they can drive fish towards shallow water, although this behaviour should not necessarily be interpreted as coordinated cooperation. In winter, flocks may include Common Goldeneyes, Buffleheads and other diving ducks.
Breeding pairs form during the spring breeding season. The female usually selects and prepares a cavity nest, lining it with plant material and down. A clutch commonly contains 6–17 eggs, which the female incubates for approximately 28–35 days. The male generally leaves once incubation begins.
The ducklings are precocial and leave the nest within a day or two of hatching. They follow the female to water and begin feeding for themselves soon afterwards. Broods may join together, sometimes forming groups containing young from several females. The female remains with the ducklings while they grow, whereas males commonly gather in separate flocks after breeding.
Identification Tips
- Look for a large, slender duck with a long, narrow, pointed bill rather than a broad, flattened bill.
- Adult males are identified by their dark green heads, red bills, clean white bodies and black backs.
- Females and immature birds have grey bodies, rusty or cinnamon-coloured crested heads, and a sharply defined white throat.
- The species often rests on rocks, logs or midstream boulders in rivers and on the margins of clear lakes.
- In flight, look for large white wing patches and a long, streamlined body.
- Red-breasted Mergansers generally have a more ragged crest, a less sharply defined transition between the head and breast, and a more extensively patterned breast. Hooded Mergansers are smaller and have a much broader, fan-shaped crest, especially in adult males.
Conservation Status
The Common Merganser is currently assessed as Least Concern on the IUCN Red List. It remains widespread, and available North American monitoring indicates broadly stable breeding numbers in that region, although local populations may vary.
Important pressures include degradation of rivers and lakes, water pollution, loss of mature trees and nesting cavities, disturbance near breeding sites, and declines or changes in fish populations. Climate change may also alter the availability of open water, prey and suitable breeding habitat.
Conservation measures include protecting riparian woodland, maintaining clean and connected waterways, safeguarding fish populations and retaining mature trees with natural cavities. Appropriately designed nest boxes can provide additional breeding sites in areas where natural cavities are limited.
Frequently Asked Questions
What is the scientific name of the Common Merganser?
The scientific name is Mergus merganser. In Europe and Asia, the species is commonly called the Goosander.
Where does the Common Merganser live?
It lives mainly on clear freshwater rivers, lakes and reservoirs across northern North America, Europe and Asia. In winter, some birds also use sheltered estuaries and coastal bays.
What does the Common Merganser eat?
Fish make up most of its diet. It also eats aquatic insects, crustaceans, molluscs, amphibians and other small aquatic animals.
Do Common Mergansers nest in trees?
Yes. They commonly nest in natural tree cavities and old woodpecker holes near water. They may also use large nest boxes and, less often, cavities in banks, cliffs, hollow logs or buildings.
How long do Common Merganser eggs take to hatch?
The female usually incubates the eggs for approximately 28–35 days. The ducklings leave the nest within a day or two of hatching and are able to swim and feed soon afterwards.
How can a Common Merganser be identified?
The most useful features are its large size, slim body, long serrated bill, white wing patches and diving behaviour. Adult males have green heads and white bodies, while females and immature birds have rusty crested heads and grey bodies.
References
- Cornell Lab of Ornithology
- IUCN Red List of Threatened Species
- United States National Park Service
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