Thanks Rhuby and Jackie! The connection between the size of the heads, completely skipped my mind (shaking head-e); it does seem rather obvious, now that you mention it.

It *is somewhat hard to call swans, geese, turkey, ducks as birds. To my mind, a bird (water bird or otherwise) must fly eihter high, or far, or frequent, to be called that. It must use its wings. These larger birds don't use their wings as much and are therefore probably clubbed together as fowl or gaming birds. Just a thought....