Cassin's Hawk-Eagle

Identificazione

The adult Cassin's hawk-eagle appears as a small eagle, with short rounded wings and a long rounded tail. It has dark brown upperparts, with white spots and a brown tail with three black bars and a broad black subterminal band. The tarsi are white with black streaks, and the underparts are all white or white with black blotches along the sides of the lower breast. It has yellowish-brown eyes, pale yellow ceres and feet and a black bill. Immature and juvenile plumage is strikingly different from that of adults. A brown or rufous head with dusky lores and streaked black on the throat and centre of the crown is typical. The underparts are white and the breast russet with half-concealed blackish spots, while the belly and flanks are marked with dense black spotting. The tail is dark gray with a white tip and dark barring and the dark brown wings have white-tipped secondary feathers. In flight, the juvenile shows pale underwing coverts whereas an adult has dark underwing coverts and a black band along the rear edge of the wing. The immature gains its adult plumage by becoming blacker above and whiter below.<p>A fairly small eagle, under current classification, Cassin's hawk-eagle is the smallest member of the Aquila genus. Measuring 50–56 cm (20–22 in) in length, it has a wingspan of 103–113 cm (41–44 in) and weighs in at 0.9–1.2 kg (2.0–2.6 lb). Strong reversed sexual size dimorphism is present, with females far larger than males.

Tassonomia

Cassin's hawk-eagle taxonomy has been in flux ever since it was first described and remains uncertain to this day. Previously, the broader taxonomy of true eagles was based on morphological similarities such as plumage patterns that yielded the 'booted eagle' (eagles with feathered tarsi) and 'hawk-eagle' contained groupings. As such, Cassin's hawk-eagle was formerly allocated to the genera Limnaetus, Phoeoaetus, Cassinaetus, Hieraaetus, and Spizaetus in no particular order. It was moved to Hieraeetus when Spizaetus was restricted to the Neotropical hawk eagles but recent molecular studies using mitochondrial DNA have shown that both of those genera are paraphyletic and that Cassin's hawk-eagle forms a clade with the larger booted eagles of the genus Aquila. Its closest relatives are Aquila fasciata and Aquila spilogaster (both formerly of Hieraaetus) which together form a distinct sub-clade of Aquila. The visual similarities with other hawk-eagles can be explained by convergent evolution but there is still some work being done on booted eagle phylogeny in general, so this may change in the future.<p>In 2017, a group of researchers proposed that the official English name be changed from "Cassin's hawk-eagle" to "Cassin's eagle", so that the term hawk-eagle could be restricted to current members of Spizaetus and Niseatus in line with the global effort to make bird names more consistent. This has yet to be implemented by most listing authorities.

Nome scientifico

Aquila africana

Autorità

(Cassin, 1865)

Ordine

Accipitriformi

Famiglia

Accipitridae

Genere

Aquila

Areale e habitat

West, central and marginally east Africa; from Sierra Leone east to western Uganda and south through the Congo Basin to northern Angola. Restricted to primary rainforest, A. africana is thought to have been more widespread in the past but its distribution has since contracted with the continued destruction of the Guinea-Congolian Forests. Repeated sightings of individuals in primary rainforest fragments in Kenya's Imenti Forest and the Ndundulu Forest in Tanzania have been interpreted as biogeographical evidence for past links between isolated forests in East Africa and those much further West. Cassin's hawk-eagle's preference for primary forest is so strong that its presence is reduced even in slightly disturbed forest and it is completely absent from secondary forest and open biomes which explains its absence between the forests.

Migrazione

Specie stanziale

Comportamento

Comportamento migratorio: Specie stanziale.

Conservazione

Tendenza della popolazione: in diminuzione.

Tendenza della popolazione

in diminuzione