What's so special about the Common Eider?
What’s so special about the Common Eider?
WRITTEN BY ASH NOBLE, COMMUNICATIONS INTERN
We know our Nature Trust supporters love birds, but what about the ones you can’t always see? Some spend their winters along the U.S. coast only to grace our Maritime shores during the spring and summer months, inhabiting some of our most remote and scenic islands to breed and raise their young. This is the case for the common eider (Somateria mollissima), the largest of all northern hemisphere sea ducks!
On our South Wolf Island Nature Preserve, the southernmost island in The Wolves Archipelago located along the Bay of Fundy, common eiders are one of the many birds to call the island home during the spring and summer months. In fact, South Wolf has received international recognition as an Important Bird Area (IBA) and an Environmentally Significant Area (ESA) for birds such as the nationally-endangered harlequin duck (Histrionicus histrionicus), as well as other species like purple sandpipers (Calidris maritima), black-legged kittiwakes (Rissa tridactyla), and great black-backed gulls (Larus marinus)!
A pair of female (left) and male (right) common eider (photographed by Christoph Moning, iNaturalist)
Learning about Common Eiders
Historically, common eiders have been best known for the quality of their feathers (otherwise known as eiderdown), whose soft and warm lining had long been harvested for filling pillows and quilts. This practice is not as common today and thankfully has not had a significant impact on conservation, as eiders maintain a current global breeding population of 2.3 million, with an estimated 750,000 breeding in North America.
Of the common eider species, the male eiders are the easiest to identify, with a sloping profile to their forehead, a white back, dark sides and belly, a black cap, and a greenish hue to the sides of their necks. The colouring of female eiders, on the other hand, is different from their male counterparts, as they are a rich reddish brown overall with a fine blackish barring, allowing her to camouflage while incubating on a nest.
Like many sea birds, common eiders live off a diet of primarily aquatic invertebrates, which can be easily found in their coastal and island habitats. In fact, adult eiders almost exclusively eat mollusks, crustaceans, echinoderms (sea urchins), marine worms, and fish eggs. Among their favourite foods are blue mussels, which they pry from underwater rocks with their chisel-like bills!
While some races of common eider vary in their migration patterns (some travelling long distances, others short, some remaining in the same area year-round) there is a significant population of eiders documented to breed along the Atlantic and Fundy coasts, as well as a small pocket in the Baie des Chaleurs in northern New Brunswick. Around the months of May and June, flocks of eider migrate to South Wolf for exactly that purpose!
Breeding on our South Wolf Island Nature Preserve
Common eiders are colonial breeders, nesting in colonies from 100 to more than 15,000 individuals. They are known to breed on coastal islands and on shorelines with grasses, mosses, and sometimes low shrubs or stunted trees, making South Wolf the perfect summertime haven for this species! Eiders make their nests in the grasslands that cover large sections of the island, creating beautiful swirling patterns in the grass.
Not only are common eider nests visually appealing, but they are also environmentally conscious! Female eiders will often reuse nests from previous years of breeding, sometimes even using nests of other waterfowl or gulls. Eiders also famously line their nests with down plucked from their own breast and belly, creating warm and cozy places for their young to incubate and hatch! Female eiders will then incubate their eggs continuously for a month, not feeding and only leaving for occasional drinks of water. It is very important not to disturb incubating eiders, as they will use up precious energy if they are forced to leave the nest.
A field of common eider nests on South Wolf. Check out these amazing swirling patterns! (photographed by Jon MacNeill)
Only 24 hours after hatching, young eider ducklings are able to leave the nest and can feed themselves, though their mothers stay with them for several weeks. These ducklings also often benefit from the care of “aunts,” which are nonbreeding females. These “aunts” watch over brooding and newly-hatched young, accompanying the ducklings to the water with their mother and helping to protect them from predators like large gulls and jaegers.
Although breeding does not begin until the spring, the romance between common eiders is a year-round affair! During periods of calm weather in autumn, male eiders begin to display, both singly and in groups, tossing their heads, stretching their necks, and flapping their wings while keeping up a soft cooing. Females respond to partners with a low cawing call, and pairs will often copulate during fall and winter, well outside of the nesting season. Common eiders also appear to be monogamous, and pairs will sometimes reunite in consecutive seasons!
Protecting Common Eiders and other bird species
At the Nature Trust, we strive to protect common eiders and every other important species of bird that calls South Wolf home, giving them the space they need to reunite and grow their families! In order to protect the essential breeding grounds that South Wolf provides, access to the island is restricted yearly from May 1 — August 31, unless by permission or with a permit from the Canadian Wildlife Service (CWS).
Although access to the island is limited, there is still a need to conduct regular surveys and collect data that will inform our future conservation actions on the island. Tony Diamond, an accomplished ornithologist, Emeritus Research Professor in Biology at UNB, and one of our stewards for South Wolf, tells us that, “Sadly, the last few times I have visited, there have been very few eiders. A thorough survey, throughout the Wolves [Islands], of eiders when they have chicks (mid-July) is long overdue.”
Want to learn more about the common eider?
Click here to access even more information about this species, courtesy of Cornell Lab!