What duck did I just see?

Welcome to a new edition of the ever-popular “Name That Bird!” game. A little while ago, I saw a duck in Boston Harbor. It was about mallard-sized, mostly black, but with white wings (at least the outer part you see while the duck is swimming), and I think white chin and neck. It was a diving duck, and seemed to stay under for at least half a minute. I also think it had something of a black crest to its head. Sorry, the details could be better, but I saw this bird at some distance. Can anyone put a name to it?

White-winged Scoter

Thanks, Colibri, though I don’t think that was it. It had more white, both on the wings and the throat. Also, possibly, a crest.

Juveniles and females have more white on the face, but are not as dark:

http://www.llcc.cc.il.us/cmcdonald/PHOTOS/wwingedscoter.jpg

Scoters are sea ducks, and spend much of their time diving. There are two other North American species, Black Scoter and Surf Scoter, but they lack white in the wing.

I feel like I’m being an unreliable witness here, but I still don’t think it was a scoter. I’ve spent the past ten minutes trolling the web, without coming to any definite conclusion. Mergansers I notice have something of a crest, but don’t typically have the amount of white I saw on the wing. So I’m still uncertain.

Was it shaped like a Merganser (long and slender, with a long thin beak) or was it chunkier with a shorter beak?

Unfortunately, I wasn’t close enough to say much about the beak. The duck was about the size of a mallard, and shaped like one, too. Again, from trolling the web, I’d be tempted to say it was a bufflehead, except that I think I was too large, and I’m pretty certain the back of its head wasn’t white.

What are the chances I saw a duck never before spotted by man? Call it Anser ammoniaci?

More importantly, did its quack echo?

A female bufflehead would be a possibility, but as you say is too small:

Other possibilities are female Common Goldeneye:

http://www.wep.ab.ca/pictures/c_geye_f.jpg

or Barrow’s Goldeneye:

The latter are closer to Mallard size

Any of these could look blackish in poor light

It wasn’t a Common Loon by any chance, was it? That’s the only black-and-white diving “duck” that I know of.

(No crest on that one either, though, and it’s a bit larger than a mallard.)

Colibri, I’m beginning to think it was a Common Goldeneye. The amount of white seems correct, and these birds are apparently common around Boston. Thanks for your help. (Incidentally, does your work as an ornithologist begin to fill you with doubt about convictions based on eyewitness testimony?)

Oh, absolutely. As chair of the Panama Rare Bird Committee, I have to evaluate all kinds of sightings. I’m used to filtering what people tell me they saw through the probabilities of what they actually might have seen. And if the details aren’t consistent, I have to guess at what part of the description to accept and what to disregard.

Several times I have had “Harpy Eagles” reported to me that happened to be Ospreys. :dubious: