Both the swan and the goose belong to the Anatidae family, whose primary members also includes ducks. Geese tend to be smaller than the much larger swans, whose maximum length can be up to six feet. Coloring on swans tends to typically be completely white or white with some black and in rare instances, all black. Geese, tend to be more of a blackish, grey or brown color, with white markings typically found on their belly or lower tail. Another noticeable difference is the longer neck of the swan, which has a notable S-shaped curve to it. Neck of geese tends to be shorter and straight.