Black Swan

Black Swan

The black swan (Cygnus atratus) is a big water bird, a species of the swan that breeds mainly in the south-east and southwestern regions of Australia.

In Australia, black swans are nomadic, with irregular migration patterns depending on climatic conditions.

It’s a big bird with mainly black plumage and a red bill. Black Swans are monogamous breeder, with both partners sharing incubation and swan-rearing duties.

Scientific classification

  • Domain: Eukaryota
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Aves
  • Order: Anseriformes
  • Family: Anatidae
  • Genus: Cygnus
  • Species: C. atratus

In the 1800s, the black swan was introduced as an ornamental bird to different countries, but it managed to escape and establish stable populations.

On the Thames River at Marlow, on the river that flows through the small town of Dawlish in Devon (they have become the emblem of the city), near the Itchen River, Hampshire, and the Tees River near Stockton on Tees, there is a small population of black swans.

Description

Black swans, with white flight feathers, are mainly black-feathered birds. With a pale bar and tip, the bill is bright red; the legs and feet are greyish-black.

With a longer and straighter bill, cobs (males) are slightly larger than pens (females). Cygnets (immature birds) with pale-edged feathers are greyish-brown.

Mature black swans vary in length from 110 to 142 centimetres (43 and 56 in) and weigh 3.7 to 9 kilograms (8.2 to 19.8 lb). 

A musical and far-reaching bugle-like sound, called either on the water or in flight, is spoken by the black swan as well as a number of softer crooning notes. It may also whistle, especially when it is disturbed during breeding and nesting.

When swimming, black swans keep their necks arched or upright and sometimes wear their feathers or wings raised in an intimidating display.

In-flight, a wedge of black swans will form as a line or a V, with the individual birds flying strongly with long undulating necks, creating whistling sounds with their wings and baying, bugling or trumpeting calls.

The black swan is different from any other Australian bird, but in a bad light and at long range it can be mistaken with a magpie goose in flight. Although, the black swan can be differentiated by its slower wing beat and a considerably longer neck.

Distribution 

Black swans are popular in the wetlands of southwestern and eastern Australia and the adjacent coastal islands.

In the south-west, it occupies an area between the North West Cape, Cape Leeuwin and Eucla; in the east, it covers a wide area surrounded by the Atherton Tableland, the Eyre Peninsula and Tasmania, with the Murray Darling Basin hosting very large populations of black swans. It is unusual in central and northern Australia.

The preferred habitat of the black swan extends through dry, brackish and saltwater lakes, swamps and rivers with submerged and evolving vegetation for food and nesting materials.

It also prefers permanent wetlands, including ornamental lakes, but can also be found in flooded pastures and tidal mudflats, and sometimes in open seas near islands or shores.

The black swan was once believed to be sedentary, but it is now understood to be extremely nomadic. There is no fixed migration pattern, but rather an opportunistic response to either rainfall or drought.

In high rainfall years, emigration from the south-west and south-east to the interior occurs, with a reverse migration to these heartlands in drier years.

When rain occurs in the arid central regions, black swans may migrate to these areas to nest and raise their young.

However, should the dry conditions return before the young have been raised, the adult birds would leave the nests and their eggs or swans and return to the wetlands.

The black swan, like a lot of other waterfowl, loses all its flying feathers at when it moults after breeding and is unable to fly for a month. It will normally settle in big, open waters for safety during this time.

The species has a wide range, with estimates of between 1 and 10 million km2, considering the frequency of the occurrence. The global population is estimated to be up to 500,000.

This large and common bird has not been reported as a threat of extinction or a major decline in the population.

Black swans were first seen by a Europeans in 1697 when Willem de Vlamingh’s expedition explored the Swan River in Western Australia.

Diet

Black Swan

The black swan is almost entirely herbivorous, and while there are some regional and seasonal variations, the diet is usually dominated by aquatic and marshland plants.

In New South Wales, reedmace leaf (Typha genus) is the most important food for birds in wetlands, followed by submerged algae and aquatic plants such as Vallisneria. 

Water plants such as Potamogeton, stoneworts and algae are the dominant foods in Queensland. The exact composition varies with the water level; in flood conditions where typical food is out of control, black swans feed on onshore pasture plants.

The black swan feeds in the same way as other swans. When feeding in shallow water, it dips its head and neck under the water and keeps its head flat against the bottom while keeping its body horizontal.

The swan ends up in deeper water to hit lower.

Reproduction and nesting

Like other swans, the black swan is predominantly monogamous, coupled for life (about 6 per cent of the divorce rate). Recent studies have discovered that about a third of all broods exhibit extra-pair paternity.

An approximate one-quarter of all matings are homosexual, mainly between males. They steal eggs or form temporary threesomes with females to get eggs, driving away from the female after laying eggs.

Black swans usually nest in the southern hemisphere during the wet winter months (February to September), sometimes in large colonies.

A black swan nest is usually a large heap or mound of reeds, grasses and weeds between 1 and 1.5 meters (3–41⁄2 feet ) in diameter and up to 1 meter high, in shallow waters or on islands.

A nest is reused yearly, restored or reconstructed as required. The care of the nest is shared by both parents. The typical clutch contains 4 to 8 greenish-white eggs that are incubated for approximately 35–40 days.

After laying the last egg, the incubation begins to synchronize the hatching of the chicks. Before the incubation starts, the parent may sit over the eggs without actually warming them. 

Both sexes incubate the eggs, and the female incubates at night. The transition between incubation periods is marked by ritualized displays by both sexes.

If the eggs mistakenly roll out of the nest, both sexes will recover the egg using the neck (in other swan species only the female performs this feat).

Like all swans, black swans are fiercely defending their nests with their wings and beaks. After hatching, the swans are taken care of by the parents for about nine months before fledging.

Cygnets can ride on their parents’ backs for longer trips to deeper water, but black swans do this less often than mute and black-necked swans.

Fun Black Swan facts

The meaning of the scientific name of the black swan is a swan dressed in black, owing to its almost completely black plumage.

A large number of black swans on the ground is referred to as a bank, but the group is called a wedge when in flight.

With just one leg, the black swan swims, tucking the other over its tail. This may be so when swimming, and it wants to flee from a predator or travel rapidly to get to the food, the swan can change course more easily.

A black swan, compared to the size of all swan species, has the longest neck.

The black swan is Western Australia’s official bird and is featured on this state’s flag and its coat of arms.

It was believed only white swans existed before European explorers entered Australia. The first European to see the remarkable sight of Australian black swans in Shark Bay in 1636 was Antounie Caen, a Dutch mariner.

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