T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Swan (Black) Cygnus atratus

Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Anseriformes
Family: Anatidae
Subfamily: Anserinae
Tribe: Cygnini
Genus: Cygnus
Species: C. atratus
Binomial name: Cygnus atratus
Synonyms: Anas atrata, Chenopis atratus
Common name: Black Swan

Cygnus atratus are native to Australia (including Tasmania) and have been introduced to New Zealand, Europe, and North America. It is New Zealand’s largest wetland bird with a mature bird around 1.2 metres in length and weighing 5–9 kilograms. The neck is long and curved in an "S"-shape. On the water, it appears all black with a bright red bill; however, in flight the bird shows wide white wing margins. The bill is bright red, with a pale bar and tip; and legs and feet are grayish-black. Cobs (males) are slightly larger than pens (females), with a longer and straighter bill. Cygnets (immature birds) are a grayish-brown with pale-edged feathers.
When swimming, Black Swans hold their necks arched or erect, and often carry their feathers or wings raised in an aggressive display. In flight, a wedge of Black Swans will form as a line or a V, with the individual birds flying strongly with undulating long necks, making whistling sounds with their wings and baying, bugling or trumpeting calls.
The Black Swan's preferred habitat extends across fresh, brackish and salt water lakes, swamps and rivers with underwater and emergent vegetation for food and nesting materials. Permanent wetlands are preferred, including ornamental lakes.
Black swans mainly eat the leaves of aquatic plants, which they reach underwater with their long necks, tail up-ended like a mallard duck. They also graze on clover and pasture close to lakes, where manure fouling makes them unpopular with farmers.
Black swans breed either in pairs or in colonies. Their nests are huge mounds of long foliage, built near lake edges. Females may lay up to 14 green eggs, but six is the average. In colonies, up to 40 cygnets gather in large crèches guarded by a few adults.
Juveniles leave their natal lake and spend several years in estuarine or coastal sites, returning to take up permanent residence once they reach breeding age – between two and four years old. Not all birds breed every year. The oldest known swan in New Zealand was at least 29.
Black Swans, like many other water fowl, lose all their flight feathers at once when they moult after breeding, and they are unable to fly for about a month (This time may vary). During this time they will usually settle on large, open waters for safety.
Before the arrival of the Māori in New Zealand, a subspecies of the Black Swan known previously as Cygnus sumnerensis, is now thought to have been the same species as the black swan. This New Zealand species of swan had developed in the New Zealand, but was apparently hunted to extinction. 
In 1864 about 100 Australian Black Swan was introduced to New Zealand as an ornamental waterfowl, and populations are now common on larger coastal or inland lakes, especially Rotorua Lakes, Lake Wairarapa and Lake Ellesmere, and the Chatham Islands. Black Swans have also naturally flown to New Zealand, leading scientists to consider them a native rather than exotic species, although the present population appears to be largely descended from deliberate introductions.
The overall populations of black swans in New Zealand are estimated at around 60,000 birds, down from 100,000 in the early 1960s. Lake Ellesmere (Te Waihora) alone had around 70,000 until the fierce Wahine storm of 1968 destroyed the lake-floor vegetation, causing swan numbers to crash. Large numbers gather at Farewell Spit each winter to moult.
In New Zealand the Black swans are partially protected, and are hunted in season according to regional limits. About 5,000 are shot each year.

Cygnus atratus in flight.


Photographed at Lake Mangamahoe, New Plymouth 

The unusal stance that swans adopt when standing on one leg.

A parent with cygnets




 

A Black swan up-ending in deeper water to reach food. A mallard duck looks on.
 

Thanks to Wikipedia for text and information     https://creativecommons.org/licenses/by-sa/3.0/