The Black swan (Cygnus atratus) is a large unmistakeble waterbird, a species of swan. It is one of only three swan species that inhabit the southern hemisphere. The Black swan was introduced to various countries as an ornamental bird in the 1800s but has managed to escape and form stable populations. It is a popular bird in zoological gardens and bird collections, and escapees are sometimes seen outside their natural range.
The body of an adult Black swan is mostly black, except for its broad white wing tips, visible in flight. Its bill is bright red, having a pale tip and bar, and its feet and legs are grayish-black. Its neck is long (the longest neck amongst swans, relative to its size) and it is curved into an "S"-shape. The males are slightly bigger than the females and have longer and straighter beaks. Juvenile Black swans are grayish-brown with lighter-edged feathers.
Black swans are natives of Australia, including Tasmania, and mainly occur in Australia's south-eastern and south-western wetlands. These birds were once thought to be sedentary, but are now known to be highly nomadic. There is no set migratory pattern, but rather opportunistic responses to either rainfall or drought. Black swans inhabit rivers, lakes, and swampland in water that is fresh, salt, or brackish. They prefer habitats that have aquatic vegetation but sometimes live in terrestrial areas like flooded fields or dry pastures when food is scarce.
Black swans are active during the day and feed in a similar manner to other swans. When feeding in shallow water they will dip their heads and necks under the water and they are able to keep their heads flat against the bottom while keeping their bodies horizontal. In deeper water swans up-end to reach lower. Black swans are also able to filter feed at the water's surface. These beautiful birds may be found on their own but they also often form loose groups consisting of several hundred or sometimes thousands of birds. They usually move in flocks, sometimes nest in colonies, and are the least territorial of swan species. They are strong fliers, traveling together in a line or V shape, beating their wings slowly, and making whistling noises. On the water as well as in flight, Black swans make a range of high-pitched, musical, bugling, baying, or trumpeting calls. They have also been heard to make a variety of softer crooning notes. If disturbed while nesting they usually make a whistling sound.
Black swans are herbivores (folivores), feeding on vegetation both in the water or in pastures, or when on farmland. Common aquatic plants they feed on include algae, leaves of reedmace, and stoneworts. Occasionally they will eat insects.
Black swans are monogamous and often have the same mate for life. They are territorial and remain in solitary pairs during mating but occasionally mate in colonies. February through September is the breeding season. Usually, the female swan makes a nest from sticks, debris, and dead leaves into a mound floating on the water. She lays 5 to 6 eggs, one day apart. Incubation starts once all the eggs are laid and lasts 35 to 48 days. Males help with incubation. The cygnets are precocial and can swim and feed soon after hatching; however, they are brooded in the nest after hatching for a period of 2 to 3 weeks. They fledge between 150 to 170 days old. Black swans can fly at about 6 months old and stay with their family group for about 9 months. They reach reproductive maturity within 18 to 36 months.
There are no major threats to Black swans, although brief hunting seasons have been instigated in some parts of their range due to crop damage caused by this bird.
According to Wikipedia, the current global population of the Black swan is estimated to be around 100,000-1,000,000 individuals, while the population in Japan has been estimated at around 100-10,000 introduced breeding pairs. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.
Black swans are important in their ecosystem, as they affect species populations that they consume, and as a food source for their natural predators.
