Swans at Alipore Zoo Swans are birds of the family Anatidae within the genus Cygnus. The swans' close 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 or seven species of swan in the genus Cygnus; in addition there is another species known as the coscoroba swan, although this species is no longer considered one of the true swans. Swans usually mate for life, though "divorce" does sometimes occur, particularly following nesting failure. And if a mate dies, or is killed by a predator, the remaining mate will take up with another; however, if all goes well in the pairing, they indeed will stay together for life. The number of eggs in each clutch ranges from three to eight. The swans are the largest members of the waterfowl family Anatidae, and are among the largest flying birds. The largest species, including the mute swan, trumpeter swan, and whooper swan, can reach a length of over 1.5 m (60 inches) and weigh over 15 kg (33 pounds). Their wingspans can be almost 3 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 swans are generally found in temperate environments, rarely occurring in the tropics. A group of swans is called a bevy or a wedge in flight. Four (or five) species occur in the Northern Hemisphere, one species is found in Australia and New Zealand and one species is distributed in southern South America. They are absent from tropical Asia, Central America, northern South America and the entirety of Africa. One species, the mute swan, has been introduced to North America, Australia and New Zealand. Swans feed in the water and on land. They are almost entirely herbivorous, although they may eat small amounts of aquatic animals. In the water food is obtained by up-ending or dabbling, and their diet is composed of the roots, tubers, stems and leaves of aquatic and submerged plants. Mute swan threatens a photographer in Toyako, Japan. Although swans only reach sexual maturity between 4 and 7 years of age, they can form socially monogamous pair bonds from as early as 20 months that last for many years, and in some cases these can last for life. The lifespan of the mute swan is often over 10 years, and sometimes over 20, whereas the black-necked swan survives for less than a decade in captivity. These bonds are maintained year round, even in gregarious and migratory species like the tundra swan, which congregate in large flocks in the wintering grounds. The nest is on the ground near water and about a metre across. Unlike many other ducks and geese the male helps with the nest construction. Average egg size (for the mute swan) is 113×74 mm, weighing 340 g, in a clutch size of 4 to 7, and an incubation period of 34--45 days. With the exception of the whistling ducks they are the only anatids where the males aid in incubating the eggs. Swans are known to aggressively protect their nests. One man was suspected to have drowned in such an attack. Source : http://en.wikipedia.org/wiki/Swan This video taken from Alipore Zoo at the time of visiting myself in April, 2014. I have taken the custom thumbnail from google images and description from wikipedia. I have not any intention to break terms of google and not want to heart anybody. If any one thinks so please write to me I will definitely correct myself.

• published: 15 Apr 2014
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