Somateria mollissima
common eider

Common eider populations nest mainly in the coastal high arctic regions of Canada and Siberia. Along the eastern coast of North America, common eiders breed as far south as Maine, and along the western coast of North America they breed as far south as the Alaskan Peninsula. During the winter, common eiders move south, rarely as far as Florida on the east coast and sometimes as far south as Washington on the west coast. Most common eiders, however, move primarily to Newfoundland and Cape Cod in the east and to the Aleutian Islands in the west. (Ehrlich, et al., 1988; Nuttal, 1929; Peterson, 1980)

Common eiders nest mainly among the rocks surrounding the coastlines and in tundra, particularly on small offshore islands that are free of mammalian predators. Nests are often hidden in tall grasses to avoid predation. (Guillemette, et al., 1992)

Measuring, on average, between 53 to 60 cm (21 to 24 inches) common eiders are the largest ducks in the northern hemisphere. Although the weight of common eiders differs depending upon the individual’s sex and the time of year, they average about 1800 grams, with reported measurements being between 850 and 3025 grams.

Adult male common eiders are recognizable by their dramatic arrangement of black and white plumage. They are black on their underside and white on their back and forewings. The male common eider also has a predominantly white head, but it is crowned with black and they have a touch of light emerald green on the back and sides of their head. The adult female common eider is almost exclusively brownish or reddish-brown and is closely barred. Immature males begin their life grayish-brown in color, then become dusky with a white collar and eventually end up like their mature counterparts. The white plumage in adult males develops in irregular patterns.

Female Common Eiders blend in well with their environment, which is the vegetation on the offshore islands. Adult plumage patterns are not fully complete until they reach about three years of age. In the period of a single year, dramatic differences in the appearance of plumage occur, which is why there is a great diversity in appearance among individuals in any given flock. (Ehrlich, et al., 1988; Nuttal, 1929; Peterson, 1980)

Common eiders are monogamous. During the spring, courtship becomes very intense and lasts even after two common eiders have paired. This ensures a strong bond between the male and the female. When courting a female in the spring, male common eiders use a series of loud, eerie calls to attract a female. These calls resemble a sort of slurred moaning "ow-ee-urr" sound. Although many common eiders are already paired with a mate by the time they reach the breeding grounds, some do not pair until they get to the islands. Pairs of common eiders do not mate for life. (AKNHP, 1998; Ehrlich, et al., 1988; National Audubon Society, Inc., 2000; Peterson, 1980)

Female common eiders reach sexual maturity earlier than males. A female may be capable of reproduction when she is around two years of age, whereas a male takes three years to sexually mature.

Nesting begins in early summer; common eiders return to breeding islands as soon as the ice begins to melt. It takes a couple of days for a pair to choose a nesting site and prepare it. The female common eider plucks down from her own body to line a nest, in which she lays four to five eggs, on average (range 2 to 8). After the second or third egg is laid, the female begins incubation. Incubation lasts for about 25 days and is only done by the female. About 50 percent of common eider eggs hatch successfully. Young fledge after 30 to 50 days. (AKNHP, 1998; Ehrlich, et al., 1988; National Audubon Society, Inc., 2000; Peterson, 1980)

The female common eider plucks down from her own body to line a nest, in which she lays four to five eggs. After the second or third egg is laid, the female begins incubation. Incubation lasts for about 25 days and is only done by the female. Unlike most other seabirds, male common eiders do very little in raising the young. In fact, male common eiders leave to join male flocks once the female has begun incubation. Young fledge in about 30 to 50 days.

After mating, protecting the young from predators becomes one of the major priorities among most individuals in a flock. One of the most noticeable behaviors to provide protection from predators is creching behavior. Common eiders gather into large groups which distract predators and may help ducklings by reducing the gull’s ability to hunt effectively. By pooling into these large groups, common eiders reduce the area exposed to the predators and thus reduce the risk of a gull picking out a single individual in the group. (AKNHP, 1998; Bedard and Munro, 1977; Ehrlich, et al., 1988; National Audubon Society, Inc., 2000; Nuttal, 1929; Peterson, 1980)

Although common eiders are capable of flight about 60 days after hatching, few young ever survive that long. Young are killed by predators, starvation, or exposure. If one duckling per couple lives long enough to make the migration flight in the fall, it is a good year. Even though this survival rate seems low, adult common eiders living in the wild have long lives, often as long as 20 years. Estimated survival rates among adults per year average from 80-95 percent. (AKNHP, 1998; Nuttal, 1929; Peterson, 1980)

Common eiders are migratory, they live and travel in large flocks which often number from tens to thousands of individuals. Common eiders dive to collect various oceanic organisms, often plunging anywhere from 3 to 20 meters into the water. They also follow a leader in the flock while diving in order to expend less energy in the winter. (AKNHP, 1998; Guillemette, 1998; Guillemette, et al., 1992; Nuttal, 1929)

We do not have information on home range for this species at this time.

When courting a female in the spring, male common eiders use a series of loud, eerie calls to attract a female. These calls resemble a sort of slurred moaning "ow-ee-urr" sound.

The diet of common eiders consists almost exclusively of mollusks, echinoderms, crustaceans, and a few fish. Common eiders swallow their prey whole and then crush them with their gizzard. During the winter months, daylight is short-lived and so common eiders spend more than half of the day feeding.

Common eiders feed by diving into the water to collect food. This behavior is done in a systematic fashion, with the leaders diving first and the rest following behind. Feeding usually only lasts 15 to 30 minutes per session and afterwards the common eiders move inland to rest and digest their food. After regaining strength, they repeat the behavior; this occurs throughout the day. When temperatures drop drastically during the winter, common eiders expend less energy and may stop feeding to conserve energy. Also during this time, common eiders improve their energy levels by becoming more effective hunters. It has been shown that during the cold months, common eiders dive and collect larger prey.

Foods eaten include: mussels, clams, scallops, sea urchins, starfish, crabs and fish. (Ehrlich, et al., 1988; Guillemette, 1998; Guillemette, et al., 1992; Peterson, 1980)

The primary predators of common eiders are Arctic foxes (Vulpes lagopus) and various gulls (family Laridae). The gulls are perhaps more of a threat than the foxes. This is because common eiders tend to nest on islands, which don’t have land predators, but gulls can fly out to the islands with no trouble. Gulls prey on the eggs and the young of common eiders, and are a major threat to the survival of the young. The threat posed by the gulls is alleviated somewhat by the creching behavior of common eiders. Gulls do, however, still prey on common eiders even during creching. Gulls will follow the flock in flight and make various swoops into the crowd to try and snag a young duckling. Similarly, while on the ground, gulls will work together. One gull will hover over a common eider who is concealing her young next to her body causing the female to jump up and attack the gull. In doing this, the female exposes her young, allowing a gull on the ground to snatch it away. (AKNHP, 1998; Bedard and Munro, 1977; Guillemette, 1998; Nuttal, 1929)

Common eiders have an impact on the prey they eat; they are also an important food source for their predators.

Common eiders are widely known for their down feathers. Although they are also valued as a sport duck and for culinary purposes, their feathers have produced a multi-million dollar industry in some parts of the world. Common eider down can be collected from nests without disturbing the eggs or the well-being of the duck. (AKNHP, 1998; National Audubon Society, Inc., 2000)

There are no known adverse affects of common eiders on humans.

Common eider populations were dramatically reduced prior to hunting regulations in North America. Some places in Canada and the arctic north even saw local extinctions of common eiders. Since the hunting laws were enacted, these areas have been recolonized by common eiders; they have even extended their breeding ranges. Common eiders are protected under the US Migratory Bird Treaty Act. (AKNHP, 1998)