The Urban Pantheist

Male and female common eiders together in the water off Castle Island, South Boston. Photos by cottonmanifesto

Urban species #339: Common eider Somateria mollissima

The winter migration brings North America's largest duck to Boston's waters. The common eider is in fact the largest duck in the northern hemisphere, living in European and Asian seas as well. Most have relatively short migrations, flying for example, from northern Britain to southern Britain or France, or from Canada to the Carolinas. Watchful eyes are on some of the Pacific populations, which migrate from Siberia to the Aleutian islands, thereby connecting Asia with North America. Avian flu could conceivably cross the Pacific by this route.

Common eiders are the most ocean-going of ducks, appearing on inland waters in only the rarest circumstances. They gather in large groups near the coast, and dive to the ocean floor for mollusks and crustaceans. Prey is swallowed whole and "chewed" by a muscular gizzard. Eider nests are composed of the down of the female, which is an excellent insulator against the arctic cold. Humans have made use of eider down for centuries. In Iceland, eiders have reportedly developed a kind of commensal relationship with humans: they seek out nesting sites near human habitations, where arctic foxes are less common. In return, the humans collect the down from the nests, replacing it with hay.

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