# Common eider

The common eider (pronounced /ˈaɪ.dər/) (Somateria mollissima), also called St. Cuthbert's duck or Cuddy's duck, is a large (50–71 cm (20–28 in) in body length) sea-duck that is distributed over the northern coasts of Europe, North America and eastern Siberia. It breeds in Arctic and some northern temperate regions, but winters somewhat farther south in temperate zones, when it can form large flocks on coastal waters. It can fly at speeds up to 113 km/h (70 mph).
The eider's nest is built close to the sea and is lined with eiderdown, plucked from the female's breast. This soft and warm lining has long been harvested for filling pillows and quilts, but in more recent years has been largely replaced by down from domestic farm-geese and synthetic alternatives. Although eiderdown pillows or quilts are now a rarity—typically being marketed as luxury goods—eiderdown harvesting continues and is sustainable, as it can be done after the ducklings leave the nest with no harm to the birds.

## Taxonomy

The common eider was formally named by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae. He placed it with all the other ducks in the genus Anas and coined the binomial name Anas mollissima. It is now placed with two other species in the genus Somateria that was introduced in 1819 by the English zoologist William Leach. The genus name is derived from Ancient Greek σῶμα sōma 'body' (stem somat-) and ἔριον erion 'wool'. The specific mollissimus is Latin, meaning 'very soft'. Both parts of the name refer to its down feathers.
Six subspecies are recognised:
* S. m. v-nigrum Bonaparte & Gray, GR, 1855 – breeds in northeast Asia and Alaska; winters in the Bering Sea and the Aleutian Islands
* S. m. borealis (Brehm, CL, 1824) – breeds in northeast Canada, Greenland and Iceland; winters in the north Atlantic
* S. m. sedentaria Snyder, 1941 – breeds in Hudson Bay and James Bay (Canada)
* S. m. dresseri Sharpe, 1871 – breeds in southeast Canada and northeast USA; winters around northwest Atlantic coasts
* S. m. faeroeensis Brehm, CL, 1831 – Faroe Islands
* S. m. mollissima (Linnaeus, 1758) – breeds in northwest Eurasia; winters in northwest and central Europe

## Description

The common eider is both the largest of the four eider species and the largest duck found in Europe, and is exceeded in North America only by smatterings of the Muscovy duck, which only reaches North America in a wild state in southernmost Texas (and arguably south Florida where feral but non-native populations reside). It measures 50 to 71 cm (19+1⁄2 to 28 in) in length, weighs 0.81 to 3.04 kg (1 lb 12+1⁄2 oz to 6 lb 11 oz) and spans 80–110 cm (31–43 in) across the wings. The average weight of 22 males in the North Atlantic was 2.21 kg (4 lb 14 oz) while 32 females weighed an average of 1.92 kg (4 lb 3+1⁄2 oz). It is characterized by its bulky shape and large, wedge-shaped bill. The male is unmistakable, with its black and white plumage and green nape. The female is a brown bird, but can still be readily distinguished from all ducks, except other eider species, on the basis of size and head shape. The drake's display call is a strange almost human-like "ah-ooo", while the hen utters hoarse quacks. The species is often readily approachable.
Drakes of the European, eastern North American and Asia/western North American races can be distinguished by minor differences in plumage and bill colour. Some authorities place the subspecies v-nigra as a separate species.
This species dives for crustaceans and molluscs, with mussels being a favoured food. The eider will eat mussels by swallowing them whole; the shells are then crushed in their gizzard and excreted. When eating a crab, the eider will remove all of its claws and legs, and then eat the body in a similar fashion.
It is abundant, with populations of about 1.5–2 million birds in both North America and Europe, and also large but unknown numbers in eastern Siberia (HBW).
A particularly famous colony of eiders lives on the Farne Islands in Northumberland, England. These birds were the subject of one of the first ever bird protection laws, established by Saint Cuthbert in the year 676. About 1,000 pairs still nest there every year. Because St. Cuthbert is the patron saint of Northumberland, it was natural that the eider should be chosen as the county's emblem bird; the birds are still often called Cuddy's ducks in the area, "Cuddy" being the familiar form of "Cuthbert".
In Canada's Hudson Bay, important eider die-offs were observed in the 1990s by local populations due to quickly changing ice flow patterns. The Canadian Wildlife Service has spent several years gathering up-to-date information on their populations, and preliminary results seem to show a population recovery. The common eider is the object of the 2011 documentary People of a Feather, which studies the historical relationship between the Sanikiluaq community and eiders, as well as various aspects of their ecology.
The common eider is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.

## Social behaviour

Eiders are colonial breeders. They nest on coastal islands in colonies ranging in size of less than 100 to upwards of 15,000 individuals. Female eiders frequently exhibit a high degree of natal philopatry, where they return to breed on the same island where they were hatched. This can lead to a high degree of relatedness between individuals nesting on the same island, as well as the development of kin-based female social structures. This relatedness has likely played a role in the evolution of co-operative breeding behaviours amongst eiders. Examples of these behaviours include laying eggs in the nests of related individuals and crèching, where female eiders team up and share the work of rearing ducklings.

## Gallery

* Adult male in eclipse plumage
* Male juvenile in first winter plumage, similar but different from eclipse plumage
* Female
* Male in flight
* Eider duck skin coat
* Traditional man-made eider nesting boxes
* Eider nest on the tundra in the Canadian Arctic
* Small eider creche: three adult females over six ducklings at Biddeford Pool, ME.
* stretching
* Common eider with ducklings swimming
* A Drake Common Eider in the Nonesuch River, Scarborough, Maine.