Black Swan

The black swan is a large waterbird that breeds mainly in southeastern and southwestern Australia, where it lives on fresh, brackish and salt water lakes, swamps and rivers with underwater and emergent vegetation. It has black plumage with white flight feathers and a bright red bill, and its S-curved neck is relatively the longest among the swans. Though once thought sedentary, it is highly nomadic, moving opportunistically in response to rainfall or drought. Pairs are monogamous and share incubation and cygnet-rearing. Birds may be found singly or in loose companies of hundreds or even thousands, and the call is a far-reaching, bugle-like sound.

About the black swan

The black swan is a large Australian waterbird and a true swan, a close relative of the white mute swan of Europe. Its plumage is black, its bill is bright red, and white flight feathers flash when it flies. It breeds mainly in the wetlands of southwestern and southeastern Australia, including Tasmania.

The English naturalist John Latham first described the bird in 1790, calling it Anas atrata. It was later moved to its own genus, Chenopis, and since 1997 it has sat in the swan genus as Cygnus atratus, with Chenopis kept as a subgenus. The species has no recognized subspecies.

At rest a black swan looks almost entirely black, but the flight feathers are white and show plainly when the wings open. The bill is a rich red with a pale bar near the tip, and the legs and feet are greyish black. The eyes are reddish or pink. Young birds, or cygnets, are greyish brown with pale-edged feathers and a lighter bill.

Black swans are big birds. Adults measure 110 to 142 cm (43 to 56 in) long and weigh 3.7 to 9 kg (8.2 to 19.8 lb), with a wingspan of 1.6 to 2 m (5.2 to 6.6 ft). Males are slightly larger than females and have a longer, straighter bill.

The neck is the standout feature. Relative to the body, it is the longest neck of any swan, and it is usually held in a curved S-shape. Rare pale birds also exist. A captive flock in Lakeland, Florida, has produced a few light, mottled-grey birds, and leucistic white "black swans" are believed to turn up rarely in the wild.

Behavior and diet

Black swans are social. They may be seen alone or in loose gatherings of hundreds or even thousands of birds, and they are the least territorial of the swans. Most activity happens by day, making the species largely diurnal, although they often feed at dusk and travel at night, calling as they fly. In flight, a group forms a line or V, and their wings make a whistling sound.

They are vocal birds. The main call is a musical, far-carrying bugle, given on the water or in the air, along with softer crooning notes. A swan disturbed at the nest may whistle. When swimming, a black swan often holds its neck arched or upright and lifts its feathers or wings in an aggressive display.

The diet is almost entirely plant-based. Swans feed on reedmace (Typha) leaves, submerged algae and water plants such as Vallisneria, Potamogeton and stoneworts, with the mix shifting by region and water level. In shallow water a swan dips its head and neck under the surface. In deeper water it up-ends, tail in the air, to reach lower. It can also filter-feed at the surface, and during floods it grazes pasture on shore. Insects are eaten only occasionally.

Like other swans, black swans are largely monogamous and usually pair for life, with a divorce rate of about 6%. Studies have found that around a third of broods include young fathered by a male outside the pair. An estimated one in four pairs are same-sex, mostly two males, which may take over nests or briefly pair with a female to obtain eggs.

Pairs strengthen their bond with a display called the Triumph Ceremony. The male approaches with wings and chin raised, calling over and over. The female answers, the two dip and raise their heads, and they finish by swimming in a circle.

In Australia, black swans nest during the wetter winter months, roughly February to September, sometimes in large colonies. The nest is a big mound of reeds, grasses and weeds 1 to 1.5 m (3 to 5 ft) across and up to 1 m (3 ft) high, built in shallow water or on an island and reused each year. A typical clutch holds four to eight greenish-white eggs, each averaging about 299 g (10.5 oz).

Both parents incubate for about 35 to 40 days, with the female taking the night shifts. Incubation begins only after the last egg is laid, so the chicks hatch together. Unusually, both sexes will roll a stray egg back into the nest with the neck. Cygnets can swim and feed soon after hatching and sometimes ride on a parent's back into deep water. The family stays together for about nine months.

Eggs are taken by Australian ravens, rats, swamp harriers and white-bellied sea eagles. Swamp harriers, sea eagles, quolls, water rats and sometimes gulls take young birds. Adults defend the nest hard with wings and beak.

Range and habitat

Black swans are common in the wetlands of southwestern and eastern Australia and nearby coastal islands. In the southwest, the range covers the area between North West Cape, Cape Leeuwin and Eucla. In the east, it stretches across a huge region bounded by the Atherton Tableland, the Eyre Peninsula and Tasmania, and the Murray-Darling basin holds very large numbers. The bird is uncommon in central and northern Australia.

They use fresh, brackish and salt-water lakes, swamps and rivers with plenty of underwater and emergent plants for food and nest material. They favor permanent wetlands, including ornamental lakes, but also use flooded pastures, tidal mudflats and occasionally the open sea near shore.

Once thought to stay put, the black swan is now known to be highly nomadic. It has no fixed migration. In wet years birds move inland from the coasts, and in dry years they move back. After rain in the arid interior, swans fly in to nest. If drought returns before the young are raised, the adults may abandon eggs or cygnets.

After breeding, a black swan sheds all its flight feathers at once and cannot fly for about a month, so it settles on large open water for safety.

The species was introduced to New Zealand in 1864 as an ornamental bird and is now common on many large lakes there. Feral or escaped birds also live in Britain, Japan and mainland China. Black swans are reported in Florida and California, but in Florida there is no evidence that they are breeding, and sightings may come from repeated releases or escapes.

Conservation status

The black swan is listed as Least Concern on the IUCN Red List, most recently assessed by BirdLife International in 2018. Its extent of occurrence is put at between 1 and 10 million square kilometers (about 0.4 to 3.9 million square miles), and the global population is estimated at up to 500,000 birds. No threat of extinction or significant decline has been identified.

The species is fully protected in every Australian state and territory and must not be shot. In farming areas, black swans can be crop pests that eat or uproot plants, and a hunting season has been set up in some places to help control their numbers.