Common eider
The Common eider (Somateria mollissima) is a large sea duck and the largest species in the Northern Hemisphere, measuring 23–27 inches (58–69 cm) in length with a wingspan of about 41 inches, distinguished by its heavy, lethargic build, long sloping bill adapted for foraging on rocky substrates, and striking sexual dimorphism in plumage: breeding males are predominantly white with black cap, back, and tail, accented by a pistachio-green nape and variable bill color (orange in western populations, olive-gray in eastern), while females and immature males are barred in warm brown and black for camouflage.[1][2][3] Native to the Holarctic region, the Common eider breeds in colonies along mid- to high-latitude northern coasts, from Alaska and northern Canada through Greenland, Iceland, Scandinavia, and eastern Siberia, with six recognized subspecies adapted to regional variations; it migrates southward to winter in shallower coastal waters, bays, and estuaries as far south as New Jersey in North America, western France in Europe, and the Kuril Islands in Asia, though some southern populations remain sedentary.[4][1][2] Its preferred habitats are rocky shorelines, islands, and tundra free from heavy predation, where it rarely ventures into freshwater except during migration; the species is highly marine-oriented, spending most of its life on or near saltwater.[1][4][2] Behaviorally, Common eiders are sociable birds that form large flocks of up to several thousand individuals offshore, with males performing elaborate courtship displays involving crooning calls and head-bobbing; they nest on the ground in depressions lined with plant material and insulating down plucked from the female's breast, often in dense colonies alongside terns for protection, laying 3–5 olive-gray eggs incubated solely by the female for 23–30 days.[1][2] Ducklings are precocial and leave the nest soon after hatching, forming communal "crèches" of up to 150 young tended by multiple adult females while biological mothers forage, a strategy that enhances survival in predator-rich environments; the diet consists primarily of marine invertebrates such as mussels, clams, crabs, and sea urchins, which are swallowed whole after being pried from rocks with the bill.[1][2][5] The global population is estimated at 3.3–4 million individuals, with significant concentrations in Europe (791,000–955,000 breeding pairs), but it has experienced moderate declines exceeding 40% in some regions over the past three decades, leading to its classification as Near Threatened on the IUCN Red List due to threats including overharvesting of eiderdown, hunting, oil pollution, habitat disturbance, avian diseases like cholera, and climate change impacts on breeding grounds.[4][1] Notably, the species' soft, dense down has been harvested sustainably for over 1,000 years for bedding and insulation, particularly in Iceland where artificial nest huts support commercial collection without harming populations.[2][1]Taxonomy
Etymology
The common name "eider" derives from the Old Norse word æþr, meaning "eider duck," which entered English via Dutch, German, or Swedish forms in the mid-18th century, with the first recorded use in 1743 referring to the bird or its down.[6][7] The scientific name Somateria mollissima was originally described by Carl Linnaeus in 1758 as Anas mollissima in the tenth edition of Systema Naturae, placing it among the ducks in the genus Anas.[8] In 1819, English zoologist William Elford Leach transferred it to the newly established genus Somateria, where it has remained without significant subsequent changes.[9] The genus name Somateria is a New Latin formation from Ancient Greek sôma ("body," stem somat-) and erion ("wool"), alluding to the bird's soft, wool-like downy plumage.[10] The specific epithet mollissima is the superlative form of Latin mollis ("soft"), meaning "very soft," further emphasizing the texture of its feathers.[11]Classification and subspecies
The common eider (Somateria mollissima) is classified within the family Anatidae, the ducks, geese, and swans, specifically in the subfamily Anatinae and the tribe Mergini, which encompasses the sea ducks.[12][13] This placement reflects its adaptation to marine environments, distinguishing it from freshwater ducks in other tribes. Within the genus Somateria, which includes the three other eider species, the common eider is recognized as a distinct species based on morphological, ecological, and genetic criteria. It is most closely related to the king eider (Somateria spectabilis), sharing phylogenetic affinities within the genus as evidenced by molecular analyses.[13][14] Six subspecies of the common eider are currently recognized, primarily differentiated by geographic isolation, subtle variations in bill morphology (such as the shape, size, and extent of frontal lobes and nasal saddle), plumage tones, and body size. These subspecies partition the species' circumpolar range across the Northern Hemisphere, with limited gene flow due to migratory patterns and breeding site fidelity. The following table summarizes the recognized subspecies, their primary geographic ranges, and key distinguishing morphological traits:| Subspecies | Geographic Range | Distinguishing Morphological Traits |
|---|---|---|
| S. m. mollissima (nominate) | Northern Europe, including Scandinavia, Baltic Sea, and northwestern Russia | Moderate-sized bill with small, triangular frontal lobes; males have a pale green nasal saddle and extensive white on the back; females show lighter barring.[13][15] |
| S. m. faeroensis | Faroe Islands and adjacent North Atlantic islands | Smaller overall size (3–15% smaller than nominate); bill with reduced frontal processes; females exhibit darker, more uniform brown plumage with finer barring; supported by mtDNA similarity to Shetland populations.[16][13] |
| S. m. borealis | Iceland, Greenland, and eastern Canada (Labrador) | Larger bill with more extensive green on the nasal saddle; males show a steeper forehead profile; body size intermediate between nominate and American forms.[13][15] |
| S. m. sedentaria | Hudson Bay region, Arctic Canada (Manitoba to Nunavut) | Long, broad bill with rounded frontal lobes extending toward the eye; sedentary populations with larger body mass; males have prominent white wing patches.[13][17] |
| S. m. v-nigrum | Siberia, Bering Sea, and western Alaska (Pacific coast) | Distinct V-shaped black feathers on the white belly in males; bill with pronounced, wedge-shaped frontal lobes; overall darker plumage tones adapted to Pacific conditions.[13][18] |
| S. m. dresseri | Northeastern North America (Maine to Labrador, Gulf of St. Lawrence) | Similar to sedentaria but smaller; bill with broad, rounded processes; males display a more extensive black cap and green nape patch.[13][17] |