Common Eider Somateria mollissima
The most numerous duck species, found throughout the whole island group in the summer period. Some few overwinter. The population is probably more than 20,000 pairs.
Features: 60-70 cm. A hardy and robust duck (1.6 to 2.8 kg). The difference in appearance regarding sex, age and plumage through the year leads to great variation. The young birds resemble females, but are more uniformly dark and lack the white wing speculum. It is not easy to separate young males from adult males in eclipse plumage (late summer plumage). Some of the male Common Eiders have plumage features as in the subspecies borealis. In these the adult males have uniformly yellow bills and have a sail (feather tips) on the back. The males of the nominate subspecies mollissima lack the sail and as a rule have a yellowish-green to blue-grey bill. Consequently, the Svalbard population is a mix between mollissima og borealis (intermediate).
Breeding: Most nest in colonies on islands and rocks where there are no foxes. The eggs are most often laid in a hollow and lined with pale grey down and material found at the site.