Questionable anser

Yesterday, doing some back-to-school shopping at the Assembly Square Mall, I went and had a look at the river, and there was this goose.  It was there again today, among a dozen-strong flock of Canada geese.  Now, there's no question about the identity of this bird:  It's Anser anser, the greylag goose.  But after that things get a bit murky.

The greylag goose is not, after all, an American bird.  It's a Eurasian species that nests in the northern half of Europe and Asia, and migrates to the south of Asia, the Mediterranean, and North Africa.  Occasionally a vagrant fetches up in North America.  Is the bird above one such?  Maybe, but it's impossible to say.  It happens that the greylag goose is the ancestor of the domestic goose, a certain number of which have gotten loose in this country and gone feral.  The domestics are usually white -- like the notorious Charles River white geese -- or splotched with white.  But not always; some have the coloration of wild greylags.  The domestics are also said to be heavier-bottomed, but again, it's hard with an individual animal out on the river to assess its bottom-heaviness.

Just based on the probabilities, this is a feral animal, maybe some generations removed from the barnyard.  And in a sense, the question is purely academic, because wild greylags and those of domestic stock are the same species anyway.  But this is the first one I've ever seen in Somerville.