Vol. 43, No. 3
This month readers were treated to an especially challenging image to identify. The only thing that can be said about the mystery species is that it is clearly a waterbird species that is capable of diving from the surface, unlike plunge divers such as Northern Gannets and terns that dive from the air. Beyond this, at first glance the picture would appear to offer little in the way of obvious features useful for identification.
That the bird appears to be black above with a row of white, button-like spots against a dark background is actually a useful clue. Additionally, the bird has white on its sides. These features at once remove dark-backed cormorants and Sooty Shearwaters as identification candidates. The presence and arrangement of the white spots on the back eliminates all of the otherwise black-and-white alcids as candidates. With these details in mind the mystery bird has to be a duck. But what kind of duck?
At this point the identification actually becomes straightforward because a male Barrow’s Goldeneye (Bucephala islandica) is the only duck that displays such distinct white spots (or white bars) against the dark background of its back. In addition, Barrow's Goldeneyes have white sides and flanks, features that also show in the picture of the mystery bird. So what may have at first appeared to be a cryptic image of an unknown waterbird actually proves to be an unfamiliar view of an otherwise easy to identify species. If the whole bird was visible it would also display a white crescent- shaped mark in front of the eye and a dark spur-like marking near the shoulder that would curve downward toward the waterline.
Barrow’s Goldeneyes are relatively uncommon winter visitors in Massachusetts, most often appearing among flocks of Common Goldeneyes on saltwater bays or along rocky shorelines at the coast. They also rarely appear inland during migration on large freshwater ponds or lakes. David Larson photographed this Barrow’s Goldeneye on January 30, 2015, in Saco, Maine.