Somateria mollissima
Britain's heaviest duck, and the source of "eiderdown".
Size: 55-70 cm | Habitat: Sea, Marsh, Estuary & Shoreline Birds | Season: All year
A bulky, thickset sea duck, the male eider is bold black and white with a pale green nape, while females are mottled brown. Rarely seen far from the coast, eiders dive for shellfish in shallow coastal waters around much of the UK.
Bulky body, wedge-shaped bill and forehead profile · black and white plumage with a pale green nape (male) · mottled brown plumage (female) · often seen in rafts close to shore
Eiders dive to the seabed to feed on mussels and other shellfish, which they swallow whole and crush in their muscular gizzard. Females line their nests with soft down plucked from their own breast — the source of "eiderdown".
Eiderdown is so effective an insulator that it has been collected from nests for centuries to fill pillows and quilts — a single female's down can weigh only a few grams but insulate remarkably well.
The Eider (Somateria mollissima) is Britain's heaviest duck, a bulky sea duck rarely seen far from the coast — males are bold black and white with a pale green nape, while females are mottled brown.
Eiders dive to the seabed to feed on mussels and other shellfish, swallowing them whole and crushing the shells in a powerful muscular gizzard. Females line their nests with soft down plucked from their own breast — the very source of "eiderdown," long prized for its insulating qualities.
Despite being a familiar and widespread coastal species, eider numbers have shown a concerning 10-year decline of around 20%, reflecting pressures on the shellfish beds the species depends on, including conflict with commercial mussel farming.
🟠 Conservation status: Amber (UK Birds of Conservation Concern 5)
Amber-listed under BoCC5, reflecting a notable recent population decline linked to pressures on the coastal shellfish beds eiders depend on for food.