The black swan (Cygnus atratus) is a big water bird, a species of swan that breeds mainly in the southeast 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 breeders, 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 centimeters (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 and several softer crooning notes. It may also whistle, especially when 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 long-range, it can be mistaken for a magpie goose in flight. However, the black swan can be differentiated by its slower wing beat and considerably longer neck.
Distribution
Black swans are popular in southwestern and eastern Australia’s wetlands and 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, tidal mudflats, and sometimes in open seas near islands or shores.
The black swan was once considered sedentary, but it is now considered extremely nomadic. There is no fixed migration pattern but rather an opportunistic response to either rainfall or drought.
In high rainfall, emigration from the southwest 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.
Like many other waterfowl, the black swan loses all its flying feathers when it molts after breeding and cannot 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 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 Europeans in 1697 when Willem de Vlamingh’s expedition explored the Swan River in Western Australia.
Diet
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 bird food in wetlands, followed by submerged algae and aquatic plants such as Vallisneria.
Water plants such as Potamogeton, stonewort, 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 percent of the divorce rate). Recent studies have discovered that about a third of all broods exhibit extra-pair paternity.
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 (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 islands.
A nest is reused yearly, restored, or reconstructed as required. Both parents share the care of the nest. The typical clutch contains 4 to 8 greenish-white eggs 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 fiercely defend their nests with wings and beaks. After hatching, the parents take care of the swans for about nine months before fleeing.
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.
