right|thumb|Common eiders in the breeding season on Texel, the Netherlands

The common eider (pronounced ) (Somateria mollissima), also called St. Cuthbert's duck or Cuddy's duck, is a large ( 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 . 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 'body' (stem somat-) and 'wool'. The specific mollissimus is Latin, meaning 'very soft'. Both parts of the name refer to its down feathers.

Subspecies

Six subspecies are recognised:

Ecology

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). Some populations are small and declining, notably the isolated Crimean population in the Black Sea is declining and of conservation concern, with only around 700–1,100 pairs.

A particularly famous colony of eiders lives on the Farne Islands in Northumberland, England. About 1,000 pairs still nest there every year. It has been claimed that these birds were the subject of one of the first-ever bird protection laws, and that the first wildlife preserve was established for them by Saint Cuthbert in the year 676, though this is not likely to be true. No mention of the hermit having any affinity with birds is found in any documents until the publication of a story about 500 years after his death. The stories told in these later works also do not involve any concerns about habitat loss or other concepts in modern nature conservation.

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.

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.

  • Common Eider Species Account – Cornell Lab of Ornithology
  • Massachusetts Breeding Bird Atlas – Common Eider
  • Eider Duck Hunting information and pictures.
  • YouTube video of Eider eating a crab
  • Feathers of Common Eider (Somateria molissima)