The Snow Goose was formerly divided into two separate species. "Snow Goose" applied to the white ones and "Blue Goose" applied to the dark ones. They overlap locally in their High Arctic breeding range so they are not subspecies. Eventually researchers used genetics to determine that these were not actually separate species, but merely color morphs of one species. The morphs are controlled by a single gene with dark incompletely dominant. Thus the two were lumped in 1983. This one is actually an "intermediate morph" with a white belly and white breast mottling. Dark morph birds appear to be increasing in the West, but remain fairly rare. This is the first I have seen in several years. A typical white morph bird is in back although it has some rusty color on its head from iron oxide staining. Note the rather large bill with a noticeable gap between the mandibles. This helps distinguish the larger Snow Goose from the similar but smaller Ross's Goose which lacks this gap. Often called a "grin patch," to me it does not look like a grin; it looks the opposite, more like a sneer or scowl. Formerly placed in the genus "Chen" but joined "Anser" in 2017 (58th supplement).
