Worldwide circumpolar in distribution, the Common Eider (Somateria mollissima) has several recognized subspecies or races, four in North America, two that regularly occur in Maine. The latin scientific name references “very soft body wool”, features relating to the female eider’s nest building habits utilizing her down feathers to line the nest. Eiderdown’s unique physical properties make it the world’s best natural insulator. The eider is the only duck that produces commercially harvestable eiderdown, with high market value as insulation in down comforters, pillows, and jackets. We do not harvest eiderdown in Maine but north of us in Quebec it is a fairly common practice. In Iceland, where the eider is revered, eiderdown farmers have maintained sustainable eiderdown farming for over 1,000 years.
Most of the eiders in Maine are the American race, Somateria mollissima dresseri, the most conspicuous waterfowl species found year-round on the coast of Maine, and the only colonial duck nester. They are almost always found in near coastal saltwater habitats, and worldwide eiders show a special fondness for arctic or subarctic coastal waters.
Common Eiders are the largest duck in the northern hemisphere with weights commonly between 1,300 – 2,660 grams (2.5 to 5.9 lbs.). Common Eiders are exceptionally beautiful birds. Males are somewhat larger than females. Male Eiders are sharply patterned in black and white and are unique among waterfowl in having the combination of white back and breast plus black belly and sides. Female eiders are brown or buff colored and are heavily barred. In the winter their brown feathers take on a deep chestnut brown hue. Both sexes have an exposed frontal process forming a Y-shaped frontal shield that reaches almost to the eye and is the basis for subspecies discrimination.
Eiders are gregarious birds rarely found very far from marine habitats. Nesting in large colonies on coastal islands and forming large groups during the nonbreeding season makes the eider a saltwater duck in all aspects of its life cycle. American Eiders nest on islands from south-central Labrador, Newfoundland, eastern Quebec, Nova Scotia and New Brunswick, Canada south through coastal Maine to Massachusetts, with occasional birds found as far south as Long island, New York, USA. Maine supports the largest breeding population in the lower 48 states, nesting in suitable habitat on over 300 of Maine’s several thousand coastal islands.
Common eiders have a long history of exploitation throughout their range, and the American race was nearly extirpated from the east coast of the United States by the end of the 19th century due to unrestricted hunting and egg collecting. Then protective bird laws were enacted. With protection this population recovered during the 20th century and is now under increasing harvest pressure in New England, necessitating changes in hunting laws to reduce the legal harvest. As with most sea ducks with similar life characteristics of the common eider, its long lifespan (with some banded birds living into their 20s), delayed maturity to first breeding, and low recruitment (heavy duckling losses to predators), eiders are considered vulnerable to sport hunting with a high potential for overharvest.
Further, in the northeast the population is also exposed to increased predatory pressure throughout the year from an increasing bald eagle population and from now frequent incursions of predatory mink and river otters to eider nesting islands. Other potential decimating effects of importance are large climate-induced changes in the Gulf of Maine profoundly impacting the eider’s food supply. The Gulf of Maine is warming faster than 99 percent of the world’s oceans, forcing the resources that live there to face unique challenges. Ever increasing populations of the invasive green crabs that thrive in warmer water are decimating Maine’s once abundant blue mussel beds. The loss of the eider’s primary food resource has influenced population numbers and profoundly affected wintering distributions.
Worldwide common eiders have experienced moderate declines which may not have been compensated for elsewhere by increases throughout the species range. In the northern portion of this specie’s range in Labrador, Newfoundland and the St. Lawrence River (Quebec) the population is believed to be stable or increasing. In Maine the breeding population has declined in recent decades because of increased predation by bald eagles and the presence of mink and river otters on important nesting islands. Maine’s wintering eider population has also been reduced or migrated elsewhere because of climate induced changes in the Gulf of Maine and apparent large-scale losses of the blue mussel. Eiders are a true sea duck and are rarely found away from the coast where its dependence on coastal invertebrates for food has brought it into conflict in some areas with mussel farmers.
There are no truly reliable population estimates for American eiders but the portion that winters along the Atlantic coast of North America is estimated to be over 250,000 birds. Given this estimate the continental population that winters in Canada may improve this estimate to 300,000 birds. These numbers are a huge improvement over the once decimated population in the late 1800s and early 1900s when Maine’s nesting population hit a low point of only 2 nesting pairs. The abolition of market hunting, humans moving off the islands to mainland life, the Migratory Bird Protection Act and other laws, and no open hunting season on this species for decades resulted in an amazing population recovery. By the 1990s Maine’s breeding population peaked between an estimated 25,000 and 30,000 pairs. The population is likely lower today than that figure now but it is still believed to be strong.
Common eiders do not breed for the first time until they are two, three, or four years old. Once they have bred for the first time, breeding activity can extend over a fifteen-year period, or more. Eiders exhibit extreme nesting fidelity to their nesting islands, returning year after year to the same island when conditions are right. Eiders can nest in very high concentrations on some nesting islands, a factor that represents a disadvantage at times when a predator or a contagious disease as avian cholera reaches a colony.
Measures of nesting and hatching success have been well-studied for this subspecies. Because of concerns for overharvest, estimates of adult male and female survival rates were conducted and revealed that annual survival rates of females were similar to historic estimates from before the decline in this region. Survival rates for males were slightly lower but still considered sustainable. We also did not detect an increasing trend in survival during the implementation of harvest restrictions.
We hypothesized that current harvest is not influencing adult survival and that potentially low duckling survival reduced recruitment to the point that reproduction could no longer replace the relatively low mortality of adults. This has been the focus of our more recent investigations. We are near the completion of a five-year study to determine if recruitment is indeed a problem for the American eider and if so, could we identify the limitations. Further, our goal was to reduce the uncertainty in these duckling survival parameters for future population modeling and evaluate the effectiveness of gull control as a management tool for increasing duckling survival in localized areas.
Our preliminary results are encouraging and suggest that localized gull control efforts do appear to have boosted eider duckling survival in our study area. These methodologies could provide a framework for achieving short term increases in eider production at key locations should a management agency consider these management tools.
Today Maine researchers and colleagues from parts of Atlantic Canada are involved in a major eider satellite tracking project looking at a wide range of population parameters. Results of this investigation should shed some light on why portions of this population of eiders is declining. Tracking this population of eiders throughout its regional range should enable us to learn more about the health of this population and the health of these marine environments already showing climate induced changes.
