Swans are birds of the genus Cygnus within the family Anatidae. The swans' closest relatives include the geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a distinct subfamily, Cygninae.
There are six living and many extinct species of swan; in addition, there is a species known as the coscoroba swan which is no longer considered one of the true swans. Swans usually mate for life, although separation sometimes occurs, particularly following nesting failure, and if a mate dies, the remaining swan will take up with another. The number of eggs in each clutch ranges from three to eight.
An adult mute swan (Cygnus olor) with cygnets in Vrelo Bosne, Sarajevo, Bosnia and Herzegovina
The genus Cygnus was introduced in 1764 by the French naturalist François Alexandre Pierre de Garsault.[6][7] The English word swan, akin to the German Schwan, Dutch zwaan and Swedish svan, is derived from the Indo-European root *swen(H) ('to sound, to sing').
Young swans are known as cygnets, from Old French cigne or cisne (diminutive suffix et 'little'), from the Latin word cygnus, a variant form of cycnus 'swan', itself from the Greek κύκνος kýknos, a word of the same meaning. An adult male is a cob, from Middle English cobbe (leader of a group); an adult female is a pen. A group of swans is called a bevy[citation needed] or a wedge.
A mute swan landing on water. Due to the size and weight of most swans, large areas of open land or water are required to successfully take off and land.
Swans are the largest extant members of the waterfowl family Anatidae and are among the largest flying birds. 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). Their wingspans can be over 3.1 m (10 ft). Compared to the closely related geese, they are much larger and have proportionally larger feet and necks.Adults also have a patch of unfeathered skin between the eyes and bill. The sexes are alike in plumage, but males are generally bigger and heavier than females. 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. Its disappearance is thought to have resulted from extreme climate fluctuations or the arrival of superior predators and competitors