Diamante di Gould

Identificazione

Both sexes are brightly coloured with black, green, yellow, and red markings. The females tend to be less brightly coloured. One major difference between the sexes is that the male's chest is purple, while the female's is a lighter mauve.<p>Gouldian finches are about 125–140 mm long. Gouldian finches' heads may be red, black, or yellow. Formerly considered three different kinds of finches, it is now known that these are colour variants of one species that exist in the wild. Selective breeding has also developed mutations (blue, yellow and silver instead of a green back) in both body and breast colour.<p>There are several "prominent rounded tubercles" with an "opalescent lustre" at the back of the gape. These tubercles are commonly (and incorrectly) described as phosphorescent in spite of much scientific evidence to the contrary. It is believed that these tubercles simply reflect light and are not luminescent.

Tassonomia

The Gouldian finch was described by British ornithologist John Gould in 1844 as Amadina gouldiae, in honour of his deceased wife Elizabeth. Specimens of the bird were sent to him by British naturalist Benjamin Bynoe, although they had been described some years before by French naturalists Jacques Bernard Hombron and Honoré Jacquinot. It is also known as the rainbow finch, Gould's finch, or sometimes just Gould. The Gouldian finch is sister to the parrotfinches in the genus Erythrura.

Nome scientifico

Chloebia gouldiae

Autorità

(Gould, 1844)

Ordine

Passeriformi

Famiglia

Estrildidae

Genere

Chloebia

Areale e habitat

Gouldian finches are native to northern Australia, in particular the Kimberley and Northern Territory.<p>Prior to the Australian government's ban on the export of Australian fauna, Gouldian finches were exported worldwide, which has resulted in viable captive breeding populations being held in many countries.[citation needed] <p>The number of Gouldian finches in the wild decreased dramatically in the 20th century due to human-caused habitat loss. The population went from hundreds of thousands in the early 20th century to 2,500 or fewer by the 1980's. The current estimated population continues to be 2,500 or fewer birds. Early research suggested that a parasite called the air sac mite was responsible for the species' decline, but the mite is no longer considered a major factor.[citation needed] The primary threat to wild Gouldian finch populations is an increase in extensive wildfires in the late dry season of its native habitat, which negatively impacts the availability of both tree hollows for breeding, and the seeds that comprise the bulk of the Gouldian finch's diet. Cyclones and climate change have also negatively impacted tree hollow availability in the Northern Territory.

Migrazione

Resident species

Comportamento

Outside the breeding season, Gouldian finches often join mixed flocks consisting of long-tailed finches and masked finches. Flocks can consist of up to 1,000–2,000 individuals. During the breeding season, they are normally found on rough scree slopes where vegetation is sparse. In the dry season, they are much more nomadic and will move to wherever their food and water can be found.<p>Like other finches, the Gouldian finch is a seed eater. They eat up to 30% of their bodyweight each day. During the breeding season, Gouldian finches mainly feed on ripe and half-ripe grass seeds of sorghum. During the dry season, they mainly forage on the ground for seeds. During the wet season, spinifex grass seed (Triodia sp.) is an important part of their diet. So far Gouldians have been recorded eating six different species of grass seed, but researchers have yet to find evidence of insect consumption.<p>Gouldian finches will usually make their nests in tree hollows. They usually breed in the early part of the dry season, when there is plenty of food available. When a male is courting a female, he bobs about and ruffles his feathers in an attempt to show off his bright colours. He will expand his chest and fluff out the feathers on his forehead. After mating, the female will lay a clutch of about 4–8 eggs. Both parents help brood the eggs during the daytime, and it is the female who stays on the eggs at night. When the eggs hatch, both parents care for the young. Gouldian finches leave the nest after between 19 and 25 days and are completely independent at 40 days old.<p>Gouldian finches have brightly coloured gapes and call loudly when the parent birds return so that they are able to find and feed their mouths in the dark nest.<p>It has been shown that female Gouldian finches from Northern Australia can control the sex of their offspring by choosing mates according to their head colour. A certain amount of genetic incompatibility between black and red-headed birds can result in high mortality (up to 80%) in female offspring when birds of different head colours mate. If the female mates with a finch of different head colour, this genetic incompatibility can be addressed by over-producing sons, up to a ratio of four males to one female. This is one of the first proven instances of birds biasing the sex of their offspring to overcome genetic weaknesses.

Conservazione

Tendenza della popolazione

stable