The black swan (Scientific Name: Cygnus atratus) is a large aquatic bird found in estuaries and waterways of Australia. As its name suggests this swan has black feathers.
While its plumage is black, its flight feathers which are only visible when it is flying, are white in colour. It has a bright red bill with a white stripe across its tip. Its eyes are red.
The black swan can vary in size from 110 to 142 cm and weigh between 3.7 to 9 kg. Its wingspan is between 1.6 to 2 meters. Male and female are similar in appearance. The male bird, however, is slightly larger than the female and also has a slightly longer and straighter bill. The lifespan of a black swan is up to 40 years.
Black swans make a high-pitched musical bugle-like sound with honks. This is most common when in flight. It also croons and makes a whistling sound if while nesting and breeding. It may hiss aggressively if threatened.
The black swan flies slowly, with its neck outstretched. It has a slow wing beat. While graceful in flight and in water, the black swan walks rather clumsily and slowly on land. For this reason it only comes onto land when food is more abundant there than in the water.
A male swan is called a cob
A female swan is called a pen
A baby swan is called a cygnet
The black swans are found in temperate to tropical lakes, rivers, estuaries and swamps of western and eastern Australia. They prefer large shallow bodies of water. Because of their large size, they also requires unobstructed waterways of at least 40 meters to use as a runway for taking-off and landing.
Black Swans do not migrate but they are nomadic, travelling from place to place in search of suitable water-bodies with an adequate food supply. They often travel at night. When flying in a group they form a line or a V-shaped formation.
Black Swans are herbivores. They eat aquatic and marshland plants and algae. These birds also eat vegetation along the shoreline.
In shallow water the bird dips its head and neck underwater in search of food. In deeper water it up-ends itself submerging up to half its body underwater.
IT is also a filter-feeder sometimes running its bill along the surface of the water to capture floating plants and small insects.
Black swans reach sexual maturity when they are about two years old. Most start breeding in their third year. Breeding can take place all year but usually occurs between February and May in tropical climates and between May and September in the cooler temperate climates.
It has been estimated that up to 33% of black swans are homosexual and that nearly 25% of all black swan couples are same-sex couples. These couples are almost always two males getting together. These males sometimes steal a nest from a heterosexual couple and raise the young as their own or one male copulates with a female and once she has laid her eggs they chase her away and raise the chicks themselves.
Scientists believe there is a biological advantage in this behaviour as it appear that there is a higher survival rate amongst cygnets (chicks) raised by male-male couples than by male-female pairs. This may be due to the fact that there is an additional male to protect them and that having chosen to be parents they are more caring than natural heterosexual pairs.
Note: Homosexual behaviour amongst animals has been observed in over 1500 species. Besides black swans, these include the giraffes, vultures, bears and dolphins.
While younger black swans may be promiscuous by having many partners, older black swans are monogamous, a male and female pairing for life.
Nests are usually constructed above the water on small islands, in tall bushes on mounds of vegetation. The nest is about one and a half meters in diameter and half a meter high. Both partners share in maintaining the nest which is restored and rebuilt each year.
The female lays between three to nine pale green or greenish-white coloured eggs. Until the full clutch of eggs is laid the parents sit on the eggs to protect them but do not incubate them by warming them. Once the final egg has been laid both parents share in the incubation of the eggs which take between 35 to 45 days to hatch.
Young swans are called cygnets. They are covered in soft grey-brown feathers for the first three to four weeks of their lives before their black feathers begin to appear. The young cygnets are looked after by their parents for about 9 months. Cygnets sometimes hitch a free ride on their parents' backs especially when travelling in deep water.
The major threats to the black swan are habitat loss, water pollution and human interference.
Feeding these birds by well-intentioned humans does more harm than good. The birds become depended on humans for food and lose their natural foraging instincts. These birds also become less wary of humans and predators. This makes them more vulnerable to attacks by dogs, cats and foxes.
Black swans are not considered threatened or endangered. It is illegal to hunt, capture or kill them.
However, in recent time, their numbers have increased to a point that they have been responsible of significant crop damage in parts of Victoria and Tasmania. For this reason the government has established a restricted hunting season for these birds to cull their numbers.
It was once thought that all swans were white. Image the shock in the western world when black swans were discovered. To them, at the time, the discovery of a black swan was more astounding than finding a unicorn in their garden.
In 1636 Antonie Caen, a sailor on board the Dutch sailing ship the Banda, first sighted black swans near Bernier Island off the south-western coast of Australia. In 1697, the Dutch explorer, Willem de Vlamingh, captured two of these birds in what is aptly known as the Swan River in Perth, Australia today. Unfortunately these birds died on their voyage back to Holland. (This painting on the left from 1796, based on an earlier drawing, shows swans on the Swan River).