On December 29 we were walking around at the Gilbert Riparian Preserve when we heard a tremendous amount of honking coming from one of the ponds – a flock of Canada Geese was in residence. This is the right time of year to spot a Snow Goose or two mixed in here, so I scanned the flock, and sure enough…
There are two very similar-looking species of white goose in North America, the Snow Goose (the larger, more common one, which I’d seen before) and the Ross’s Goose (the smaller, less common one, which would be a new life bird for me). The usual way to tell them apart is by examining the head and bill. Ross’s Geese have rounder heads and shorter bills. Their bills have some bluish or greenish coloring around the base and typically don’t have the black “grin” that a Snow Goose’s bill does. To further complicate things, the two species hybridize pretty regularly. So what’s this one? I wasn’t sure, and since Ross’s Goose would be a lifer, I posted the (admittedly crappy) photos on Twitter and Facebook. On Facebook I directed my question to an old college birding buddy who’s now a PhD student in ornithology, while on Twitter I just posted a general plea for help, which led to someone there forwarding the photos to an ornithologist acquaintance of his own.
Rebecca Deatsman (@rdeatsman) December 30, 2012
The bill coloration looks Ross-ish, but in that last photo the head shape and bill size look more Snow-ish. My Twitter follower and his ornithologist friend decided it might be a hybrid. My ornithologist buddy from college, on the other hand, declared that to be a cop-out and put his money on Ross’s Goose, albeit maybe one with a slightly bigger bill than normal. When I checked eBird and saw that someone else had reported a Ross’s Goose at the Gilbert Water Ranch the same day, I decided to call the bird in these photos my life Ross’s Goose.
Yes, birders really do spend their time thinking about and debating this sort of thing. Here are a Snow Goose and a Ross’s Goose so you can make your own comparison. What do you think?