Thứ Tư, 15 tháng 8, 2012

Black swan

Cygnus atratus

Photo by Rosie Perera (My Swan)

Common name:
black swan (en); cisne-preto (pt); cygne noir (fr); cisne negro (es); trauerschwan (de)


Taxonomy:
Order Anseriformes
Family Anatidae


Range:
This species originates from Australia, being mostly found in the southern and eastern parts of the country, including Tasmania. Since the 19th century the black swan has been introduced in New Zealand, Japan, western Europe and North America.


Size:
Black swans are 110-142 cm long and have a wingspan of 160-200 cm. They weigh 3,7-8,7 kg.


Habitat:
These birds are found in fresh water, salt water and brackish wetlands, including lakes, rivers and swamps, preferring areas with aquatic vegetation. They are also found in flooded fields and even in dry pastures when food is scarce.


Diet:
Black swans are mainly herbivorous, eating sub-aquatic foliage, namely of Typha, Potamogeton, Myriophyllum, Ruppia and various algae. They also eat plants on pastures and farm land and are known to occasionally eat insects.


Breeding:
Within their native range, black swans breed in February-September. They are largely monogamous and most often pair for life. Typically, the female builds the nest, a floating mound of sticks, dead leaves and debris, on shallow water or sometimes in small islands. There she lays 4-8 greenish-white eggs, which are incubated by both sexes for 35-48 days. The precocial chicks leave the nest 2-3 weeks after hatching and are able to feed themselves, but only fledge 5-6 months after hatching and may remain with their parents for even longer. During this period they are protected by their parents and in the first weeks they may even ride on their backs.


Conservation:
IUCN status - LC (Least Concern)
This species has a very large breeding range and the global population is estimated at 100.000-1.000.000 individuals. The population is suspected to be stable in the absence of evidence for any declines or substantial threats.

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