Cackling geese, commonly referred to as cacklers, look essentially identical to the Canada goose. Other than size, I've an impossible time telling them apart. There are numerous subspecies of cacklers as well as "lesser Canadian geese" and all other sorts of interesting distinctions you can read about elsewhere.
Usually these fly in smaller flocks, or singles. For all intents and purposes, it doesn't really matter to tell them apart from Canada geese. They're also a dark goose, they taste fine, you can shoot them.