Geoscience Reference
In-Depth Information
An eider duckling (left) rests warmly among the down plucked from its mother's breast, and a newborn pips its egg
(right).
These islands are the stronghold of the eider duck in North America. Some 25,000 pairs breed on the more
than twenty islands that stem the tide in the Lower Estuary, and a further 5,500 breed on the shores and islands
of the gulf itself. Although these numbers are impressive, they were once far greater if the historical reports are
to be believed. When the pioneering bird artist John James Audubon visited Île Biquette in 1833, he wrote in
his journal: “So abundant were the nests of these birds on the islands that a boat load of their eggs might be
collected if they had been fresh; they are then excellent for eating.”
In fact, the excellent culinary qualities of eider eggs almost led to the species' demise. Egging of these is-
lands seriously depleted the eider population, and hunting also had an impact, since eiders are the largest of
North America's sea ducks and are therefore also highly prized for the table. It took the passage of the Migrat-
ory Birds Convention Act of 1917 to slow the depredation and carnage. The breeding numbers have since re-
bounded in the estuary, where nearly 90 percent of the breeding birds are found on five islands: Île Biquette,
Île aux Fraises, Île Blanche, Île aux Pommes, and Îles du Pot-àl'Eau-de-Vie. Of these, Biquette harbors the
greatest number of nests—some seven thousand in total.
The birds form dense breeding colonies, with more than four hundred nests per hectare. Eiders begin laying
in late April, and nearly all nests have eggs by June. The female constructs her nest on the ground from grass
and seaweed and lines it with large amounts of down feathers, which she plucks from her breast. (The bird's
scientific name reflects the qualities of its down: Somateria meaning “body wool,” and mollissima, “very
soft”.) She lays four to six large, olive-colored eggs, which are kept warm by the super-insulating properties of
the down and her own body. The brooding female leaves the nest only for a few minutes at a time while she in-
cubates the eggs, and during these four weeks she does not eat. After breeding season, the promiscuous males
do not take part in the incubating or rearing of the young, but instead return to the water, their handsome black
and white markings creating a dramatic sight wherever the birds gather off the coast in large “rafts.”
The precocial ducklings leave their nests within hours of hatching and with their mothers make immediately
for water. It is a perilous first journey, for they must run a gauntlet of predatory herring and great black-backed
gulls, which often nest on the same islands. It is, as nature writer Franklin Russell once observed, “a mathem-
atical experiment in survival”—an experiment in which the odds are stacked heavily against the duckling. A
study on Île aux Pommes revealed that 63.3 percent of nests were destroyed by predation, 14.1 percent were
