So, Canada Geese used to be easy. Big brown goose, black neck and head, white cheek patch--you know, Canada Goose. Branta canadensis, in the scientific lingo. There were a bunch of subspecies--more-or-less isolated populations, the ones who bred in the far north generally smaller--but those were pretty esoteric for most birders.
About a decade ago, the ornithologists decided that some of those smaller northerly subspecies were in fact a separate species, the Cackling Goose. (Branta hutchinsii, for those of you keeping score at home.) So now there's two species, each with several subspecies, and it's quite hard to tell which is which. So now if a birder is looking at a small white-cheeked goose, they have a problem.
Anyway, Cackling Goose is a fairly unusual visitor in this area--there was some excitement about the one that showed up in Flushing Meadow Park in January--but a Lesser Canada is almost unheard of. In fact, some prominent voices on the NY State Birds mailing list said there was "zero percent chance" of it being a Lesser Canada. Apparently, the Lesser Canada Goose _never_ shows up this far East. And we know his because it never has before. And we know that because any similar goose that does come around here isn't a Lesser Canada, but some other goose, because Lesser Canada Geese never occur here. See?
The email exchanges went on,some in the stiffly polite manner that the scientifically-inclined use when they're losing their tempers. So a couple of days later I went to see the goose. It took a while to find it, just because i had to walk most of the way around the Reservoir before I ran into the particular flock of Canada Geese it was hanging around with, but when I found them, it stood out a mile.
picking him out of a lineup
Much smaller than the somewhat smallish Canadas it was with, maybe 2/3 their size or less. Small head, small beak, very short neck, didn't associate closely with the bigger geese--even when it was in the middle of the flock, there was usually a good twenty feet separating it from the nearest other goose. Kind of dark on the "white" areas.
closest approach to a regular Canada Goose
I don't know. It looks like a Cackling Goose to me. But what do I know?
our suspect with a Shoveler, a pretty small duck
...and with a Ruddy Duck, a very small duck
I see on the mailing lists today that the goose is still around, and has been joined on the Reservoir by another very small goose, who is not so brown. So there's excellent opportunities for further dispute.
And on twitter, I see a report that the British Ornithologists' Union has added the Lesser Canada Goose to its list of species that have been seen in Britain. Except that what they're calling "Lesser Canada Goose" is B. hutchinsii, what we over on this continent, where they come from, call Cackling Goose. Because why not?