Eider
- In the common eider, nasal glands shrink so much that the contours of the head become noticeably altered after prolonged (more than one year) stays in freshwater habitats.
- The common eider exhibits pronounced sexual dimorphism: males have a white head with a black cap, pale green nape, and glossy black underparts, rump, and tail, while females are brown with transverse and longitudinal stripes.
Age
Common eiders can live from 28 years and 4 months to 47 years and 3 months, with a maximum lifespan of 24 years and 7 months, and a theoretical lifespan ranging from 26 years and 7 months to 38 years; the species reaches sexual maturity between 7 months and 3 years. The eyes of a chick open at birth, and during the "Embryo" stage, the embryo develops inside an egg and does not feed itself. Following hatching, the "Chick" stage lasts from 1 day to 2 months and 1 week, with the young being covered in thick down and soon leaving the nest. The "Rapid Growth Juvenile" stage begins after the young starts flying and lasts from 2 months and 1 week to 2 years, during which time it learns to find food independently. The “Adult” stage, when the bird is capable of reproduction, lasts from 2 to 20 years.
Phenotype
The common eider has a short beak used for catching food, and the young have a similar short beak; the young’s down is thick and retains body heat in cold water. After a period of rapid growth, the species' plumage becomes dark brown, aiding in camouflage from predators. The adult has a short, strong yellow-green beak with a growth at the base, and webbed feet for good swimming. The adult’s plumage is white on the chest and sides, with black markings on the back, head, and tail. The adult female uses very thick and warm down on her chest, which she plucks for nest building.
Physiology
Common eiders measure between 50 and 71 centimeters in body length, with a weight ranging from 1.93 to 1.99 kilograms, and a wingspan of 0.98 meters; the embryo stage has a body length of 6 to 8 centimeters and a body mass of 70 to 95 grams, while the chick stage exhibits a body length of 15 to 35 centimeters and a body mass of 60 grams to 0.9 kilograms; the stage of rapid growth shows a body length of 40 to 55 centimeters and a body mass of 0.9 to 1.6 kilograms, and the adult stage reaches a body length of 53 to 71 centimeters and a body mass of 1.7 to 2.8 kilograms.
Habitat
Common eiders inhabit river mouths where rivers flow into the sea, characterized by slightly salty water, abundant fish, and birds; they also occupy flooded meadows with plentiful grass, shallow coastal waters with crabs, taiga forests featuring spruce and pine trees, and tundra environments with short summers and extensive moss. The species’ landscape preferences include freshwater sources, marine environments, coastal waters, the benthic coastal zone, and the near-shore bottom zone. They live at elevations up to 100 meters. The climate is characterized by cold seas where water is almost always cold, potentially freezing in winter and not warm in summer, constant wetness with frequent rainfall, very cold temperatures with abundant snow and ice, a rainy and cool summer with snow in winter, and snowy winters.
Shelter
Common eiders are found on coastal islands and tundra shorelines; the species builds or uses nests, which are structures built for laying eggs and raising young. The nest is constructed from grass and down.
Geography
Common eiders are found within the Nearctic realm, the Palearctic realm, the marine realm, and the freshwater realm. The species inhabits ecosystems including the Baltic Sea, the North Sea, the Norwegian Sea, and the Northwest Atlantic continental shelf of the United States.
Feeding
The common eider dives underwater to collect food from the seabed and swallows its prey whole, employing an active hunting strategy; its diet consists of mollusks, crustaceans, sea urchins, starfish, amphipods, copepods, euphausiids, valvatiids, beetles, flies, butterflies, decapods, ribbon worms, polyplacophorans, and many other invertebrates. The species’ daily food requirement ranges from 150 to 350 grams. Bears and eagles prey on the eiders.
Reproduction
The common eider’s embryo develops for 4 weeks, and the female builds a nest on the ground where she lays eggs and incubates them alone for about a month. A brood consists of 3 to 6 young, which immediately go to water after hatching. The species reaches maturity from 2 to 3 years of age, and the female reproduces once every year. She constructs a nest on the ground and lays eggs, and she has broods of 3 to 6.