Over the past few weeks, large numbers of Canada Geese have been accumulating in Donaldson Park, my local patch. I have consistently seen over 500 at a time; yesterday the number was close to 800. The geese are attracted to the park's large athletic fields, especially to the newly-landscaped soccer fields on the east side of the park. The county laid out a banquet of fresh turf, and the geese have come to enjoy it.
Flocks that large are bound to attract other visitors. Occasionally a Snow Goose will drop in. Brant, too, have appeared at times. Yesterday a Cackling Goose joined the flock.
Here is a portion of the flock, with crows in the background. The Cackling Goose is on the right side of this image. It appears much smaller than the neighboring Canada Geese, even the ones behind it.
This digibinned photo shows the Cackling Goose in close comparison with two Canada Geese. Its back seems grayer, and it has a much shorter neck. As in the other shot, it appears much smaller than the birds behind it. I have photos of the goose with its head raised here and here. Its bill is not as stubby as I would like, but it appears to be within the accepted range for this species. It also has a relatively blocky head.
As for the subspecies, I think the most likely is Richardson's Cackling Goose (Branta hutchinsii hutchinsii). This is the most common one on the East Coast, and I see nothing here to rule that out. Richardson's Cackling Geese breed in Arctic Canada, primarily Nunavut and the Northwest Territories, and winter in the central and eastern United States.