Overview
The Common Eider (Somateria mollissima), celebrated across northern maritime lore and arctic culture simply as the Eider, is a massive, heavy-bodied, and biologically extraordinary sea duck belonging to the family Anatidae. Holding the undisputed crown as the largest and heaviest duck in the northern hemisphere, this majestic marine fowl is renowned worldwide as the primary biological source of ‘eiderdown’—the warmest, lightest, and most insulating natural down feather material known to humankind.
Displaying striking sexual dimorphism, the breeding drake is a breathtaking sight: sporting a creamy-white mantle and breast with a soft rosy-pink wash, a jet-black belly and flank, a velvety black crown, and delicate pistachio-green nape patches flanking a long, sloping, wedge-shaped greenish-yellow bill. The female is cryptically cloaked in rich barred warm cinnamon-brown. Flawlessly adapted to freezing sub-zero marine environments, common eiders dive to depths of over twenty meters into roaring arctic tide races to wrench blue mussels from rocky reefs, swallowing them whole and crushing the stone shells in their massive muscular gizzards. A cultural and economic pillar of northern coastal communities for centuries, the common eider is an enduring emblem of arctic wilderness.
AT A GLANCE
- Common Name: Common Eider
- Scientific Name: Somateria mollissima
- Category: Birds
- Subcategory: Waterfowl
- Size: Length 50–71 cm (20–28 in); wingspan 80–108 cm (31–43 in); the largest duck in Europe and North America
- Weight: 1.2–2.8 kg (2.6–6.2 lb), with females reaching peak mass prior to nesting
- Lifespan: 15–20 years in the wild; maximum recorded longevity exceeds 25 years
- Diet: Carnivorous benthic diving specialist feeding on hard-shelled marine mollusks (blue mussels, clams, periwinkles), crabs, sea urchins, and starfish
- Habitat: Rocky coastal islands, storm-swept fjords, shallow marine bays, tidal mudflats, and open arctic lead waters with abundant blue mussel beds
- Range: Circumpolar Arctic and subarctic coasts, native across the northern coastlines of Europe, Scandinavia, Iceland, Greenland, northern North America (Alaska and Canada), and Siberia; winters south to the British Isles, Baltic, and northeastern United States
- Conservation Status: Near Threatened
Biology and Physical Characteristics
Morphologically, Somateria mollissima is built for deep diving in freezing subpolar seas. Its most diagnostic physical hallmark is its head profile: its bill is large, heavy, and wedge-shaped, sloping seamlessly into the flat forehead with long, feather-covered frontal lobes extending far forward down each side of the bill, minimizing bare skin exposure to freezing arctic spray. Its body is dense, stocky, and buoyant, insulated by a thick layer of subcutaneous fat and a dense under-carpet of world-famous down feathers; these down feathers possess unique microscopic interlocking barbules that trap stagnant air pockets with unmatched thermal efficiency. Its feet are massive, set far back on the body, and equipped with broad webbing that propels the duck through surging ocean currents. Its gizzard is colossal and lined with rock-hard keratinous plates, capable of exerting hundreds of pounds of pressure to pulverize thick mussel and crab shells into fine powder.
Behavior and Ecology
Behaviorally, common eiders are gregarious marine birds that spend virtually their entire lives on coastal ocean waters, gathering in colossal offshore flocks numbering in the thousands. When foraging over mussel reefs, the entire flock dives in coordinated, synchronized waves, swimming with their wings and feet down to twenty meters to pry shellfish off granite rocks before resurfacing together. Nesting occurs from May to July on offshore islands free from mammalian predators, where thousands of females gather in dense colonies. The female constructs a shallow ground scrape, lining it with an enormous cushion of soft down plucked directly from her own breast. During her 26-day incubation period, the female does not eat or drink a single mouthful of food, losing over forty percent of her body weight while relying entirely on stored fat reserves. Once hatched, ducklings are led directly to the ocean, where multiple mothers pool their broods into massive communal ‘crèches’ guarded by cooperative adult females.
Conservation and Human Impact
The Common Eider is classified as Near Threatened on the IUCN Red List of Threatened Species, driven by significant regional population declines across parts of the Baltic Sea and North Atlantic caused by avian influenza, shifts in benthic prey quality, oil spills, and drowning in commercial fishing gillnets. In Iceland, Scandinavia, and Canada, human coastal communities have practiced sustainable ‘eiderdown harvesting’ for over a thousand years: farmers construct sheltered nesting boxes and protect wild nesting colonies from arctic foxes and gulls, gently gathering the precious down from the nests only after the ducklings have hatched and departed for the sea, sustaining a famous, eco-friendly luxury industry.
Interesting Factoid
A mother common eider is one of nature’s ultimate devoted moms—she sits on her eggs in freezing arctic gales for an entire month without eating a single bite of food, losing almost half her total body weight, while resting on a luxurious bed of down feathers she plucked right off her own chest!