Thanks folks for trying to figure out the mystery bird – and congratulations to those who were right and/or close. This was a tough bird to figure out, especially since the most obvious field mark (and the one most regularly used to conclusively id the bird) wasn’t visible.
So what can we conclude from the original photograph? Well – unless this bird is acting very unusually this must be some sort of diving duck, loon or grebe. The body shape doesn’t quite look right for a loon – perhaps a little too football-like. And the neck is a little short and thick for a grebe. The clear line between the whitish neck and brownish head doesn’t quite fit the look of a grebe as well. So, by a process of elimination, we can assume that this probably is a diving duck of some sort.
Dabblers we can ignore right away, so moving through the diving ducks we need to find something that has a white collar and a dark head. The female Common Merganser has a brownish head and a bit of contrasting white, but again, the football shape body doesn’t work with the longer shape of a merganser. Three other possibilities present themselves: Bufflehead, Barrow’s Goldeneye and Common Goldeneye. The second photo of the original post could be used to eliminate the Bufflehead since you can’t really see any white on the head of the diving bird and the sides aren’t quite white enough for a breeding male.
So we’re left with Common Goldeneye or Barrow’s Goldeneye. This is where things get a little difficult since the bird is a first winter male and isn’t showing the clear markings that a adult male in breeding would show. Barrow’s and Common can be separated using the scapulars (the white on the wings) but care has to be taken because the two species do hybridize. Commons tend to have more white on the scapulars with a thin black border while Barrow’s have more black on the scapulars with well defined white squares. The scapulars of the diving duck look to me to be more white than black. The Sibley Guide to Birds doesn’t show this very well but in the National Geographic Field Guide to Birds the Common Goldeneye looks quite different.
Of course I had the advantage of seeing the bird before and after it dove. The white spot behind the bill is a little undeveloped but looks more round than the crescent shape that is a recognizable field mark for the Barrow’s Goldeneye. This duck looks pretty good for Common Goldeneye (Bucephala clangula).
In this case I also had a fairly good look at the bill of the duck from a position of height (it was low tide so the duck was below me). Common Goldeneye tend to have a bill that looks straighter from the side than the Barrows. From above it appears broader throughout and ends with a rounded spatulate tip. In addition, the shape of the head suggests Common as well, sloping up from the bill rather than rising abruptly. Sibley has a great description of these features and how to use them to distinguish female goldeneye from each other but some of the field marks (like bill and head shape) can be used for immature males as well.
Congratulations to those of you who narrowed this bird down to one of the two goldeneye! If it makes you feel any better, I’m not sure that I would have been able to figure out which species it was without seeing the duck’s head. And even now I’m second guessing my identification!
If you’re interested in more bird related posts check out I and the Bird, edition #144 hosted by Greg Laden’s Blog on February 17th. FYI – Island Nature will be hosting I and the Bird on March 3, 2011! Send me an email with your birding post!