African Bonelli's Eagle
| African Bonelli's Eagle | ||||||||||||
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African Bonelli's Eagle ( Hieraaetus spilogaster ), juvenile |
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| Scientific name | ||||||||||||
| Hieraaetus spilogaster | ||||||||||||
| ( Bonaparte , 1850) |
The African Bonelli's Eagle ( Hieraaetus spilogaster ) is a bird of prey from the family of the hawk-like (Accipitridae). This relatively small, powerful and very agile eagle inhabits dry, rocky regions of Africa south of the Sahara, where it feeds on small to medium-sized vertebrates . The African Bonelli's eagle was long considered a subspecies of the Bonelli's eagle ( Hieraaetus fasciatus ), which also occurs in western and southern Europe .
Appearance
The African Bonelli's eagle is a rather small representative of the Aquilinae. Its body length is between 55 and 62 centimeters, large females can reach a wingspan of 150 centimeters. The reverse sex dimorphism common in birds of prey is only moderately pronounced. Females are on average 5 percent larger and 20 percent heavier than male individuals. There are only minor differences between the sexes in terms of plumage color.
At a distance, adult African Bonelli's eagles appear monochrome dark black-brown, almost black, on the upper side and white on the lower side. The long tail and the small head clearly separated from the body are also striking. Up close, small white spots can be seen on the top, especially in the coat area and on the shoulder feathers. In the seated bird, the dark slate-gray hand wings contrast clearly with the significantly darker color of the rest of the upper side plumage. The long tail is also dark slate-gray and finely banded crossways in black on the upper side; at the end it shows a wide black subterminal tape closed with a narrow white border. Females are dashed relatively densely in black on the white underside; this black mark is less pronounced in males. In both sexes, however, the insides of the lower leg fletching ("pants") and the under tail coverts are pure white. The legs are feathered up to the greenish-yellow, strong toes. The claws are black, the iris is dark yellowish-amber, the wax skin is yellowish or greenish-yellow.
Fledglings are dark brown on top with some fine black dashes on the head and neck; the underside is almost monochrome warm ocher to reddish brown and only in the neck and chest area differently distinct black lines. The tail, which is reddish-brown on top, is banded in a striking dark gray. African Bonelli's eagles are slowly changing to adult clothing; They are not colored until the age of four.
In flight, the relatively small head and long tail in the silhouette allow a certain possibility of confusion with the similarly sized honey buzzard , but the coloring and flight characteristics are so different that, given sufficient observation conditions, it should always be possible to distinguish them. In flight, the wings are largely stretched and not heavily fingered. African Bonelli's eagles fly with powerful, rather flat wing beats and glide with their wings largely horizontal. The black under wing-coverts show irregular white lines and spots; they contrast clearly with the light gray wings. There is a very bright window at the base of the wings. The arm and hand wings are clearly broadly bordered with black. The light gray tail is indistinctly darkly speckled underneath and is closed by a wide black subterminal tape and a narrow white border.
Young birds also appear much lighter in flight; their reddish-brown under wing-coverts are edged blackish. The tips of the arm and hand wings have no black border, and the distinctive subterminal band has not yet formed.
distribution and habitat
The African Bonelli's eagle is a widespread bird of prey south of the Sahara, but it occurs in very different densities. It is extremely rare in some regions. To the south, its distribution area extends roughly to the Tropic of Capricorn , which is only exceeded significantly to the south in southern Mozambique , southern Botswana and central Namibia .
In this large area of distribution, the species inhabits dry, often rocky habitats with only sparse trees. In line with this preference for dry, open habitats, it only occurs at high altitudes in the tropical belt around the equator . In East Africa it is absent in rain-favored areas and in largely arid landscapes. Occasionally it also breeds near cultivated land and in plantations. Breeding occurrences exist up to altitudes above 3000 meters, but the majority are at altitudes below 1500 meters.
Breeding birds remain in the breeding area throughout the year; Young birds roam around.
Systematics
The closest relative of the African Bonelli's eagle is the Bonelli's eagle ( H. fasciatus ). Ferguson-Lees & Christie separate both as separate species and consider them to be representatives of a superspecies . The molecular genetic studies by Lerner & Mindell support the species status of both forms. The genetic distances between H. fasciatus and H. spilogaster were even somewhat greater than those between other twin species among the birds of prey, such as between the Lesser Spotted Eagle and the Greater Spotted Eagle or between the Little Eagle and the Australian Blue Eagle ( H. morphnoides ). However, Lerner & Mindell point out the need for further research.
No subspecies are described of the African Bonelli's eagle.
Food acquisition and food
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The African hawk eagle is a powerful hunter whose hunting strategies are more reminiscent of a large hawk than an eagle. It usually hunts from a hidden hide, often at water holes or on trees along watercourses, and hits the prey on the ground. Birds, and occasionally bats, are less common in the air. He also hunts in low flight between trees and bushes and tries to use the surprise effect. Couples occasionally hunt cooperatively, with one partner isolating a bird in a flock that the other is trying to hit.
The main prey animals are birds and small to medium-sized mammals. Smaller numbers of snakes and lizards, especially young birds, also eat insects. Among the birds, large ground birds such as francolin , bustard and guinea fowl, as well as hornbills play a special role. Among the mammals, dikdiks , hares , mongooses and hyrax are common prey animals. African Bonelli's eagles can overwhelm animals up to three times their own body weight; this corresponds to a maximum prey weight of 4 kilograms. Carrion is eaten, but African Bonelli's eagles are rarely seen on carcasses.
Breeding biology
No information is available on the age of sexual maturity or the type and duration of the couple bond. The courtship and pair bonding ritual includes, in addition to the partners circling together over the nest location, among other things, impressive sightseeing flights with swooping and flying into each other, during which the claws are occasionally presented.
The breeding season in West Africa is between February and June, in East Africa north of the equator between October and March, and south of the equator usually between June and October. The nest is a massive structure made of branches and twigs. It usually measures a good meter in diameter and is often over a meter high. The outside is covered with fresh branches. It is usually at heights between 9 and 15 meters in a fork in the trunk or on a strong side branch; Nest locations along watercourses are preferred. The main nesting trees are acacias , baobabs and eucalyptus trees , but other tall tree species can also be used as nest locations. The species rarely breeds near the ground on bushes, occasionally on rocky outcrops and in individual cases on high-voltage pylons. The clutch consists of 2 (1–3) eggs; The chicks hatch after about 43 days; the nestling period lasts up to 71 days. Nothing is known about possible cainism ; there is also no information on the time of flight and dismigration of the young birds.
Existence and endangerment
There is no reliable information on the size of the world population. The IUCN classifies the species as 
(= least concern - not endangered) due to its large distribution area . Reliable figures are also lacking for the development of the population; Ferguson-Lees & Christie, however, assume a population decline in the entire distribution area, especially in West Africa.
swell
Individual evidence
- ↑ a b Ferguson-Lees & Christie (2001) pp. 753 and 755
- ↑ HRL Lerner, DP Mindell: Phylogeny of eagles, Old World vultures and other Accipitridae based on nuclear and mitochondrial DNA . Molecular Phylogenetics and Evolution 37; 2005: pp. 327-346.
- ↑ a b Ferguson-Lees & Christie (2001) p. 754
literature
- James Ferguson, David A. Christie: Raptors of the World. Houghton Mifflin Company Boston, New York 2001, ISBN 0-618-12762-3 , pp. 750-755; Plate 83.
Web links
- Aquila spilogaster in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed on December 18 of 2008.