The Northern Hemisphere species of swan have pure white plumage, but the Southern Hemisphere species are mixed black and white. Its disappearance is thought to have resulted from extreme climate fluctuations or the arrival of superior predators and competitors. The biggest species of swan ever was the extinct Cygnus falconeri, a flightless giant swan known from fossils found on the Mediterranean islands of Malta and Sicily. The sexes are alike in plumage, but males are generally bigger and heavier than females. Adults also have a patch of unfeathered skin between the eyes and bill. Compared to the closely related geese, they are much larger and have proportionally larger feet and necks. Their wingspans can be over 3.1 m (10 ft).
The largest living species, including the mute swan, trumpeter swan, and whooper swan, can reach a length of over 1.5 m (59 in) and weigh over 15 kg (33 lb). Swans are the largest extant members of the waterfowl family Anatidae, and are among the largest flying birds. Due to the size and weight of most swans, large areas of open land or water are required to successfully take off and land.
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