Poiana augure

Identificazione

Augur buzzards are one of two larger Buteo species native to Africa, alongside their cousins, the similarly sized jackal buzzard. Adults measure about 48 to 60 cm (19 to 24 in) with a large wingspan of 120 to 150 cm (3 ft 11 in to 4 ft 11 in). Males weigh from 880 to 1,160 g (1.94 to 2.56 lb) while females weigh from 1,100 to 1,330 g (2.43 to 2.93 lb). A small sample of 5 augur buzzard weighed an average of 973.2 g (2.146 lb) while 22 birds averaged 131.5 cm (4 ft 4 in) in wingspan. The adult augur buzzard is strikingly plumaged and essentially unmistakable if seen well. It is an almost black brown above with a rufous tail that stands out strongly in contrast. The primary flight feathers are blackish and the secondaries off-white, both barred with black. Below the chin and around the throat is mainly white, and the rest of the underparts and the underwing coverts are rich rufous. The flight feathers from below are white, tipped with black to form a dark trailing edge to the wing.<p>The juvenile augur buzzard is mainly brown above and rufous brown below and on the tail. It can be confused with wintering steppe buzzard, but the augur is considerably larger and bulkier with broader wings and a heavier flight style and an unbarred undertail. Although not as dark as the adult on the back and upperwing coverts, it is usually noticeably darker than a juvenile steppe buzzard. The adult augur buzzard has white underparts and underwings. The female has black on the lower throat. Juveniles are brown above and buff below, the underparts later becoming white. Juveniles are similar to juvenile jackal buzzards but are generally much paler below with bolder carpal patches and more clearly barred secondaries and tail. There is a melanistic form of augur buzzard, all black, except for grey and white flight feathers that are barred black and contrast strongly with the black center and a chestnut tail. About 10% of birds are melanistic, but the proportion rises in forested areas with high rainfall to as much as 50% in some areas. A somewhat similar melanistic morph of jackal buzzard is also known and these birds can very hard to distinguish, perhaps only told apart by the stronger barring on the melanistic augur pale flight feathers. Dark morph long-legged buzzards may also be confused for melanistic augur buzzards but are clearly more slender in the wing, less blackish on the body and lack the bold rufous tail.

Tassonomia

The taxonomy on this species is not settled, with some taxonomists considering this species, the jackal buzzard, and Archer's buzzard to be within the same superspecies. As noted by taxonomists, each species is fairly distinct, having different calls and variations in plumage. While the augur and jackal have rarely been considered actually conspecific, the Archer's buzzard is sometimes considered improbably as a subspecies of the jackal buzzard despite a number of outward distinctions and having a rather allopatric and restricted distribution. The three species may be classified as belonging to a species complex. In 2022, the International Ornithological Congress tentatively assigned Archer's buzzard as being a subspecies of the augur buzzard (Buteo augur archeri). However, it may simply represent a color morph.<p>Presently, two subspecies are recognized:

Nome scientifico

Buteo augur

Autorità

(Rüppell, 1836)

Ordine

Accipitriformi

Famiglia

Accipitridae

Genere

Buteo

Areale e habitat

The augur buzzard is found in eastern and southwestern Africa. Despite its erratic-seeming distribution, it is often common in its range. The augur buzzard is found from eastern Sudan and Ethiopia (also northern Somalia, inhabited by the subspecies B. a. archeri) down through the northeast of the Democratic Republic of the Congo, Uganda, Kenya, parts of Tanzania into Zambia, Malawi, Zimbabwe, Mozambique, western Angola and west-central Namibia. Despite its wide range in southern Africa it appears to only occur in South Africa as a vagrant. The augur buzzard is found in open or light wooded upland areas but can also range into lowland deserts at sea level (such as in Namibia) and some more mountainous, precipitous areas of eastern Africa. They seem to prefer to hunt in elevated savanna grasslands, high moorland, cropland sometimes into open forest or desert edges as well. Augur buzzards in east Africa usually live between 400 and 4,600 m (1,300 and 15,100 ft) elevation but normally occur above 1,500 m (4,900 ft) and have been recorded living at 5,000 m (16,000 ft) in Ethiopia.

Migrazione

Resident species

Comportamento

Pairs have noisy aerial displays, including outside the breeding season. Their call is quite different from their cousin, the jackal buzzard, and most other birds of prey, being a harsh, resonant crow-like a-kow a-kow a-kow or a-ung a-ung a-ung, drawn out as aerial display escalates into a longer, higher-pitched a-waaa a-waaa a-waaa. Pairs of augur buzzards usually mate for life but some polygamy has been reported in the species. The large (up to 1 m [3 ft 3 in] wide) stick nest is built in a tree or on a crag, and is often reused and enlarged in subsequent seasons. On average two (sometimes only one and rarely three) creamy or bluish white eggs are laid and incubated by the female only, although food is brought to her on the nest by the male. The eggs hatch in about 40 days, and after a further 56–60 days the chicks can attempt flight. At 70 days they become independent of the nest, but young birds may then be seen with the adult pair for some time. As is the case in other tropical raptors, the clutch size is relatively smaller and the reproductive cycle is relatively longer than in related species found in the temperate zones.<p>The diet of the augur buzzard is quite varied and opportunistic, as is typical of most Buteo species. It catches most of its prey on the ground, either by still-hunting from perch or swooping down from a soaring flight or, occasionally, from a hovering flight. They may also forage on the ground for both insects and small vertebrates. The primary foods for augur buzzards seem to include either small, terrestrial mammals or reptiles, chiefly snakes and lizards. Other prey may include small ground birds (and sometimes the nestlings, fledglings or unwary adults of varied birds), insects, and road-kill. In Zimbabwe, 59% of the diet was reptiles while the remainder was mostly mammalian, led by vlei rats. At one nest site there, lizards made up 35% of the foods and snakes 46%. In Tanzania, the stomach contents of augur buzzards similarly consisted mostly of assorted rat species and lizards. In the above Zimbabwe study, the most often taken reptiles recorded the giant plated lizards and common flat lizards but could extend to larger and more dangerous prey such as Nile monitors (though doubtfully large adults) and highly venomous snakes such as puff adders, night adders and Mozambique spitting cobras. Elsewhere mole-rats may be preferred, such as in Kenya, and these are likely hunted largely from flight as their tendency to stay in the cover of tall grasses makes them difficult to still-hunt. Occasionally larger prey are hunted including francolins, domestic chickens, hares and hyraxes, although other than rare cases mainly the juveniles of these prey types are targeted (especially in the case of Cape hyraxes).

Conservazione

Tendenza della popolazione

stable