Common Eider (Somateria mollissima)

Eider down, the soft feathers used by the female to line her nest is one of the best insulating materials known and is harvested for sleeping bags and quilts. It can be collected without harming either the birds or their eggs, making it a valuable renewable resource.

Description

The common eider is a large sea duck, measuring up to 68 cm, with striking plumage. This is the only duck in Canada that is white on top and black underneath. Its back, neck and breast are white, while its belly, tail and secondary feathers are black, as is the cap on its head. Its bill is long and yellow and it has a pale, greenish patch on the back of its head. This striking colouration is only found in adult male eiders; females are a uniformly barred dull brown, while immature males display various combinations of brown and white.

Distribution

Common eiders are abundant in northern Canada; they breed along the shores of all three oceans as well as on the coast of Baffin Island. In the Maritimes, eiders nest along the coasts of Newfoundland, the Gulf of St. Lawrence, and the Bay of Fundy. Northern populations of eiders migrate to the Atlantic or Pacific coasts to winter, while more southern maritime populations are sedentary and overwinter in their breeding areas.

Ecology Common eiders are very gregarious birds; every aspect of their life is carried out in groups, numbering from tens to thousands. They are sea ducks, diving up to 20 m deep to search the ocean floor for mollusks, other invertebrates and occasionally fish. Flocks of eiders choreograph their dives, those in front submerging first, followed by those behind. They feed intensely for 15-20 minute periods and then move further offshore, where they float and digest their meals before returning to feed once again. In cold weather, common eiders group together so closely that they cannot even be counted!

During the mating season, male common eiders court females with long, lonely calls that can sound eerie when heard in a colony of several thousand birds. Nests are built on offshore islands and lined with the world-renowned eider down. The female lays 4-5 buffy to olive-coloured eggs, which she incubates for 25-30 days without help from the male. Female common eiders must accumulate food reserves before the breeding season begins, because they do not feed or drink during courtship or incubation and must rely on stored fat. After the eggs hatch, the young are cared for by ‘aunty’ ducks while the exhausted and half-starved females rest, feed and prepare to migrate. Unlike most other ducks, eiders have a low rate of reproductive success- only 50% of eggs hatch successfully, and usually only one offspring per pair reaches the wintering grounds successfully. After their first season, however, the survival rate of eiders is very high and they may live for 20 years, allowing them to produce many more offspring.

Eiders undertake a moulting migration- after females begin incubating their eggs, males move north to a different area to moult. During the period when their new feathers are growing in, these ducks are flightless and very vulnerable to predation. Before moulting, therefore, eiders move to a protected area where they can roost safely out of the reach of predators and have access to the nutritious food they need to grow their new feathers. Female eiders also moult, but only after the breeding season. As a result of their extra migration, males reach their wintering grounds later than females and juvenile ducks. Humans have long prized the common eider, both as a food item and as a source of eider down, one of the best insulating materials known. Hunting caused drastic reductions in eider populations until laws such as the Migratory Birds Act restricted duck shooting to certain areas and seasons. Nowadays, collection of eider down is being developed as an alternative source of income in northern Atlantic communities and as a result, people are becoming more conscious of the need to protect the eiders. Thanks to these efforts, the population of common eiders is growing rapidly and their range is increasing in many areas.