Is a common eider a duck?

Yes, the common eider is a species of duck. The common eider, whose scientific name is Somateria mollissima, belongs to the genus Somateria in the duck, goose and swan family Anatidae. As a member of the Anatidae family, the common eider is considered a true duck.

Characteristics of the Common Eider

The common eider is a large sea duck that measures 50–71 cm (20–28 in) long with a wingspan of 81–115 cm (32–45 in). It weighs 1.5–3.3 kg (3.3–7.3 lb).

The male common eider has black and white plumage. Its head, neck, breast and mantle are white while its flanks are black. The female common eider is brownish. Adult females have brown, black and buff plumage. Both sexes have a wedge-shaped bill that is orange with a yellow or greenish base. They have short necks and rounded heads.

During the breeding season, the male common eider’s striking black and white plumage serves to attract females. The common eider’s dense feathers provide insulation and waterproofing in cold water. The common eider is a strong swimmer, using its webbed feet to propel itself underwater while hunting mollusks and crustaceans. Its legs set far back on its body provide an efficient swimming stroke.

Habitat

The common eider inhabits coastal marine habitats in the Northern Hemisphere. Its breeding range extends across Arctic regions like Iceland, northern Scandinavia, Siberia and Alaska. It winters south of its Arctic breeding areas in temperate coastal waters and intertidal zones.

During the breeding season, the common eider nests on islands, along shorelines and on tundra close to water. It favors small islands with sloping shorelines and vegetative cover. Outside of breeding season, the common eider can be found in both saltwater and freshwater habitats like estuaries, bays, inlets and lakes.

Diet

The common eider is an omnivorous bird that feeds by diving underwater to depths of 18 m (60 ft). Its diet is dominated by mollusks like mussels and clams. It uses its strong bill to crush the shells of its prey before swallowing them whole. Some other food sources are:

– Crustaceans: crabs, shrimp, barnacles
– Echinoderms: sea urchins, sand dollars
– Fish
– Polychaete worms
– Aquatic insects
– Some plant material like seeds and aquatic vegetation

Reproduction and Life Cycle

The common eider reaches sexual maturity at 2-3 years old. It forms monogamous pairs during a courtship process in late winter before migrating to the breeding grounds.

Nesting occurs close to the sea, often on small offshore islands. The female selects the nest site and builds the nest alone. The nest is a shallow scrape lined with vegetation and down feathers plucked from the female’s breast.

The female lays 3-6 pale olive or greenish-brown eggs. Only the female incubates the eggs for 22-28 days. The eggs hatch over 2-3 days. The young leave the nest shortly after hatching and are led by the female to the sea within 24 hours.

The young remain with the female for protection and warmth for several weeks. The male leaves before incubation starts and does not participate in rearing the young. The ducklings fledge at 50-60 days old but may remain with the female until fall migration. Most common eiders become sexually mature at age 2-3.

Relationship to Other Waterfowl

The common eider belongs to the same genus, Somateria, as two other eider species: the king eider and spectacled eider. Some key facts about their relationships:

King Eider

– Closest relative of the common eider
– Slightly larger in size
– Males have bold black and white plumage like the common eider
– Occurs farther north in Arctic regions like northern Alaska and Canada
– Does not overlap in range much with the common eider

Spectacled Eider

– Smaller in size than common eider
– Males have white plumage with greenish-black markings around the eyes
– Only found in northern Alaska and eastern Siberia
– Globally threatened species due to declining population
– Does not overlap in range with the common eider

The common eider, king eider and spectacled eider are all in the subfamily Somateriinae along with other sea ducks like the Steller’s eider. They are grouped together based on shared features like their blunt bills adapted for mollusk feeding and dense, waterproof plumage.

Comparison to Similar Duck Species

The common eider belongs to the tribe Mergini, sea ducks that feed by diving underwater. Here is how the common eider compares to some other diving ducks:

Scaup (Greater and Lesser)

– More rounded head shape compared to wedge-shaped eider head
– Blue bill color instead of orange/green bill
– Males have gray backs and white undersides versus black-and-white eider plumage
– Often found on freshwater lakes while eiders live along coast

Long-tailed Duck

– Longer, pointed tail feathers unlike the short tail of the eider
– Colorful pink/black bill in breeding plumage
– Males have black and white plumage with elongated tail feathers
– Winters farther south than the common eider

Surf Scoter

– Males entirely black with colorful orange, white, and black bill
– White patches on forehead and nape
– Smaller size than common eider
– Found along Pacific and Atlantic coasts

White-winged Scoter

– Larger size than common eider
– Males mostly black with white secondary wing feathers
– Females brown like female eiders but with darker cap and white around bill
– Seen along Great Lakes and migratory flyways

Conclusion

In summary, the common eider is definitively classified as a species of duck within the waterfowl family Anatidae based on its:

– Membership in the duck subfamily Anatinae
– Close relationships and similarities to other diving duck species in the Mergini tribe
– Characteristic features of ducks like its bill shape, webbed feet, and waterproof plumage

So the answer is yes, the common eider is a true duck, specifically a large sea duck well adapted to its marine Arctic habitat through its strong swimming ability, insulating feathers, and diet of mollusks and other invertebrates. It is an iconic waterfowl species along northern coasts and islands.