Here you see a raft of about 70 common eiders, our largest native duck, yesterday afternoon out in Blue Hill Bay at low tide.
The eiders were in the area of the reversing falls and they were probably waiting for the workers on the new bridge over the falls to leave. Then, they would swim up the falls’ channel and dive for crabs, starfish, and shellfish. In the past, they also would gorge themselves on Atlantic blue mussels, which disappeared there and elsewhere around here.
The eiders yesterday were mostly bronze females with a few black and white males. (See also the Leighton Archive image below.) Rafts of them have been wintering in this area for many decades, perhaps centuries. Nine years ago, I counted about 400 eiders (Somateria mollissima) rafting in that area.
Leighton Archive Image
Although not classified as endangered, eider numbers have been declining each year for at least a decade throughout their entire Atlantic coast range. The causes of the decline are not fully known, but research indicates that warming waters may be part of the problem. Perhaps it also is the decline of Atlantic blue mussels, the birds’ favorite food, which have been declining, apparently due in part to the warmer waters (and the voraciousness of the eiders).
Another apparent cause of eider decline is that more bald eagles are staying north in the warming winters; eagles are significant eider predators, especially eider ducklings. And, of course, big and beautiful eiders are favorite targets during duck-hunting season. (Primary image taken in Blue Hill, Maine, on December 21, 2023.)