Eider Duck

Somateria mollissima

The common eider is the largest duck in the Northern Hemisphere. A large body size is advantageous for birds like the common eider which rely on body reserves for incubation. The common eider sits on her eggs 99% of the time during the 25–26 days of incubation and only leaves to drink. However, the common eider eats before laying the eggs and whilst it is still laying eggs. One day passes between the laying of the eggs, and the development of the embryos halts until the female starts to incubate; therefore, all of the eggs hatch at the same time.

2. Most ducks in Iceland migrate from the temperate zone, with their main wintering grounds in the British Isles and in Western Europe. Conversely, the common eider originally comes from the Arctic and is settled in Iceland. Nevertheless, the common eider has also reached regions that are more southern; it breeds, for example, in the British Isles and in Scandinavia, and winters in Wadden Sea.

3. The common eider is divided into between five to seven sub-species. This is uncommon amongst ducks; normally, there is no geographical distinction between populations of the same species.

4. The common eider (and other eider ducks) uses its wings to swim below the surface, just like guillemots and penguins. Most other diving ducks, e.g. the tufted duck and the greater scaup, use only their legs.

5. The common eiders lays fewer eggs than most other ducks (4–5 instead of 8–10), but the young are proportionately bigger, in relation to the size of an adult bird, than other ducklings. (The harlequin duck represents an intermediate, laying 5–8 eggs.) This is an adaptation to bringing up the ducklings on the sea as opposed to on freshwater.