A large waterfowl of the genus Cygnus (family Anatidae), up to 1.5 m long with a wingspan of 3 m or more, those in the northern hemisphere being predominantly white and those of the southern hemisphere black or black and white. Swans are mainly herbivorous, but eat some invertebrates. They feed in water by up-ending to obtain roots, tubers, stems, and leaves of aquatic plants, and also feed on land. There are seven species found in the temperate northern hemisphere, South America, Australia, and introduced into New Zealand.