It has a growth (tumor?) on its forehead which distorts the true shape of the bird's head profile, slightly complicating its subspecific identity. Otherwise, this is a pretty good example of a Richardson's Cackling Goose, though a bit on the darker-breasted side. If anyone has any comments on the bird's subspecific identity, please feel free to comment.
Note the frosty gray-brown feather bases on the upperparts, which set off the darker subterminal lines. Seeminglingly blocky head despite the growth. Short, stubby bill. Wide white cheek patch.
Just as easily picked-out by upperpart color as by size.