Nibbio pettonero

Identificazione

Intermediate in body size between the well-known larger wedge-tailed eagle (Aquila audax) and the smaller little eagle (Hieraaetus morphnoides), the black-breasted buzzard is one of Australia's largest birds of prey and one of the world's largest kites alongside the red kite, which is slightly less heavy but has a longer total length. An adult black-breasted buzzard measures 51 to 61 cm (20 to 24 in) in height including its short square tail. The buzzard's outstretched wingspan measures 141 to 156 cm (4 ft 8 in to 5 ft 1 in), rendering the bird distinctive in flight as its wings are conspicuously long relative to its stout body and tail. Buzzards appear sexually monomorphic (identical in physical appearance), although the adult female is slightly larger, weighing approximately 1,330 g (2.93 lb) compared to the 1,196 g (2.637 lb) of the adult male. The weight range for the species is from 1,150 to 1,600 g (2.54 to 3.53 lb). It is most closely related to the Square-tailed kite (Lophoictinia isura).<p>The black-breasted buzzard is striking in appearance due to the distinctive markings of the adult plumage. From the underside, the mainly black colouring of the body and wings is contrasted by thick white panels near the end of the wings. From above, the black plumage is broken by a rich mottled red across the back and shoulders. Birds in the immature and juvenile phases of growth display pale brown colouring, with dark to black streaks increasing with age. Chicks have white coloured down, described as ‘hair-like’ on their heads. Adult birds may be individually identified during flight by broken or missing flight feathers, or when perched closely together by subtle differences in the red of the back and shoulders.<p>The common call of the black-breasted buzzard is described as a repeated hoarse yelping or short sharp yap or yelp. Adult females also make a soft drawn-out wheezing call to solicit their mate to copulate, undertake nest-building, forage for food and defend the nest. Young buzzards also use a wheezing call to solicit food from their parents.

Tassonomia

Nome scientifico

Hamirostra melanosternon

Autorità

(Gould, 1841)

Ordine

Accipitriformi

Famiglia

Accipitridae

Genere

Hamirostra

Areale e habitat

The black-breasted buzzard is widely but sparsely distributed throughout northern and inland Australia in areas with less than 500 mm annual rainfall. The buzzard's range stretches from north-eastern South Australia, north-western New South Wales, northern Queensland, the Northern Territory and the north-western exterior of Western Australia. The buzzard does not occur in Victoria, the Australian Capital Territory or Tasmania, due to their wetter temperate climates.<p>Found to occur in wooded and open habitats, the black-breasted buzzard is most commonly observed in riparian forests and tall-open woodlands surrounded by mid-dense shrublands. In a study of raptor habitat association in central Australia, it was most commonly observed in River Red Gum (Eucalyptus camaldulensis) open woodland, demonstrating a significant preference for this habitat type.

Migrazione

unknown

Conservazione

The current IUCN Red List ranks the black-breasted buzzard of Least Concern. While it is not listed as a conservation concern by the Australian Commonwealth, it is listed as Vulnerable in New South Wales and Rare in South Australia. Recent studies have assessed the black-breasted buzzard as one of many avian species of particular conservation concern in the Western Division of New South Wales. The global population estimate for the black-breasted buzzard is uncertain, varying between 1000–10,000 individuals.<p>There has been a significant decline amongst Australian raptor species including the black-breasted buzzard since European settlement in the late 1700s. Historic records indicate the black-breasted buzzard became extinct in some areas of its former range by as early as the 1930s. Causes of population declines in raptor species of the arid and semi-arid regions of Australia include broad-scale landscape changes due to extensive pastoralism and clearing of native vegetation; overgrazing by stock, feral animals and increased kangaroo populations; altered fire regimes; the introduction of destructive feral predators such as the house cat (Felis catus) and red fox (Vulpes vulpes); and the cessation of traditional Aboriginal hunting and land management practices. Intense periods of drought through the 1900s and 2000s are known to have compounded the impacts on already stressed raptor communities.<p>Inadvertent poisoning of raptors through ingestion of prey killed by toxins is a well-known threat to raptor species worldwide and a likely contributor to their decline in Australia. Such toxins are frequently introduced to the environment by humans to combat pest animals and plague insects. Other potential causes of decline include direct persecution by humans in the form of illegal egg collection and shooting which has been recorded in a number of Australian raptor species, for example the osprey (Pandion haliaetus) in South Australia. and Europe and the Tasmanian wedge-tailed eagle (Aquila audax fleayi).<p>Climate change leading to increased periods of drought in the arid and semi-arid areas of Australia is a concern for the survival of many raptors species, particularly those with specialist diets dependent on a limited array of prey species. The black-breasted buzzard has a varied diet including carrion that may afford it some resilience in the face of intense drought when carcasses of perished large mammals become abundant. However, it also has a year-round preference for living and nesting in the riparian zones of creek lines and drainage channels. As these tend to dry up under drought conditions, resultant habitat loss is likely to threaten the buzzard's reproductive viability and survival. More frequent and intense wildfire events will also increasingly contribute to the decline of large trees and potential black-breasted buzzard habitat.<p>A program of landscape conservation that engages all land managers and stakeholders and includes the protection of existing habitat and revegetation of lost habitat, is considered the first step in protecting the black-breasted buzzard, its relatives and the overall biodiversity of arid and semi-arid Australia.

Tendenza della popolazione

declining