African Crowned Eagle

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Image:AfricanCrownedEagle.jpg

Common Name: African Crowned Hawk-eagle
Scientific Name: Stephanoaetus coronatus

Size: 31-39 inches (80-99 cm); Wingspan: 59-71 inches (151-181 cm)

Habitat: Africa; widespread resident of sub-Saharan Africa, occurring in easternmost Sudan and South Sudan, western Ethiopia, southernmost Senegal, Guinea-Bissau, Guinea, Liberia, Côte d'Ivoire, Ghana and southern Togo, southern Nigeria and Cameroon, through Gabon, into Congo and Democratic Republic of Congo, south to north-western Angola, east to Uganda, Kenya and Tanzania, south-east through Zambia, Malawi and Mozambique, to northern and eastern Zimbabwe, north-eastern, eastern and south-eastern South Africa and Swaziland.

It inhabits forest, woodland, savanna and shrub land, as well as some modified habitats, such as plantations and secondary growth, and can persist in small forest fragments. It shows high resilience to heavy deforestation and degradation in some areas, although such changes are assumed to cause local declines in population density.

Status: Near Threatened. Global population: 5,000-50,000 adult individuals with a decreasing population trend. Although the species is welcomed by foresters in some areas, it is subjected to a number of significant threats throughout much of its range, including deforestation (carried out for timber extraction, charcoal production, the encroachment of agriculture and plantations, shifting cultivation and mining), competition from humans for prey species (with apparently unsustainable levels of exploitation for bush meat in some areas), direct persecution in an estimated 90% of its range (e.g. for food, arrow-fletching, witchcraft, ornaments and its pest status and threat to humans) and human disturbance. In Ghana, it is threatened by deforestation and hunting, including of its main prey. Some once-occupied areas in Ghana have now been almost totally deforested, whilst others, such as Bosomoa Forest Reserve, have been converted to teak plantations. The species may have altered its diet to partly accommodate declines in primate abundance in parts of Ghana, but its population is unlikely not to have been affected by such a dramatic decline in its prey base (which has probably worsened further since the mid-1990s). Although the species appears to be doing well at Udzungwa, Tanzania, it may be absent as a breeding species from several areas (e.g. Uzungwa scarp, Kising’a-Rugaro, New Dabaga), owing to prey depletion by humans. In Nigeria, it seems likely that the population has been impacted by widespread forest clearance in the south of the country.

Diet: Mammals; the usual prey taken shows pronounced regional differences. Throughout its range the principal prey items are small ungulates (such as duikers, chevrotains), rock hyrax and small primates such as monkeys. Birds and large lizards are rarely taken.

Nesting: Sexes are alike; however females are 15% larger. The adult crowned eagle is quite strikingly plumaged. Its crown is dark to rufous-tinged brown with a prominent, oft-raised black-tipped double crest, which can give the head a somewhat triangular appearance. The upperparts of an adult are a blackish brown-grey color, with a variable tinge of blue. The throat is brown while the belly and breast are white overlaid densely with blackish bars and blotches, variably marked with cream or rich buff-rufous coloration. The wing primaries are white at the base, broadly tipped with black and crossed by two black bars. The tail is black with brownish-grey bands. The thighs and legs are barred and closely spotted with black and white. The underwing coverts of adults are a bold chestnut coloration, spotted lightly with black. The adult crowned eagle has eyes that can range from yellow to almost white, a cere and feet of an ochre-yellow color and black talons.

Juveniles have strikingly different looking plumage compared to the adults. Much variation occurs as the maturation process occurs. A great majority of juveniles have a white head and underside, which contrast with the thighs and legs, which are heavily spotted with black. The juvenile eagle’s back is light-brown or grayish-brown, with pale feather edgings that often give the back a scaled appearance, especially on the upper-wing coverts. There is often a pinkish red wash on the upper chest. Just-fledged chicks tend have dark patched faces, freckled bibs and slightly barred chests and spotted legs. Less common juvenile crowned eagle plumages, possible even when they are under a year of age and still under parental care, may include eagles so stripy that they could easily have been aged as two to three-year olds. The tail of the juvenile is black with three pale bars and a narrow black tip. The juvenile eagle’s cere is grey and the feet are dull-yellow. By 4 months post-fledgling, the inner thighs, previously poorly covered with downy type feathers, are covered with small feathers. While the pale 'morph' young just prior to leaving the nest usually have unmarked tarsus, they soon get spots on the front part of the tibio tarsal joint. The tibio tarsal pad is still bare and obvious up until it is a year old, whereupon it vanishes only to return to incubating females. Eye color is variable too with some having khaki light brown just prior to fledging and others with adult-like yellow ochre eyes. Up to 15 months after leaving the nest, the immature eagles more closely resemble the plumage they have at first independence than the adult’s plumage. The juvenile may be confused with the similarly-colored juvenile martial eagle, especially in flight. It is distinguished from the martial species in having a much longer, more heavily barred tail, much shorter wings and spotted thighs.

The male performs an elaborate rise-and-fall display over the forest canopy both during the breeding season and outside it as a territorial proposition. Usually, territorial displays, which outnumber breeding displays, occur around the periphery of the bird’s home range while breeding displays are likely to be over or at least near the nest. Displays consist of a series of steep dives and ascents, with a few wing-flaps at the top of each climb and descending circles and figures of eight. During descents, eagles can drop as much as 60 m (200 ft.) at a time before circling back up. During this display, the male is noisy, uttering a shrill kewee-kewee-kewee while throwing his head back, often calling for a spell of approximately 30 seconds. The displaying male may reach heights exceeding 900 m (3,000 ft.), sometimes even near cloud level at over 2,000 m (6,600 ft) above the ground. The adult female may also perform independent display flights, uttering a lower kooee-kooee-kooee. The female seems to display less often and tends to have a mellower voice. Pairs also perform visually-striking mutual displays, sometimes arising from the first type or when the pairs come together after a brief absence. Spectacular tandems, interlocking talons and falling some distance from the sky are typical of mutual displays.

Crowned eagles have one of the most prolonged breeding cycles of any bird. It is common for raptors that live around the tropics to have a relatively elongated breeding period. Crowned eagle pairs breed once every two years; a single breeding cycle lasts for approximately 500 days in duration. Most other eagle species complete a breeding cycle in less than six months, or in about 35% of the time it takes the crowned eagle.

After engaging in the breeding display described above, the pair collaborate in building a massive nest in a fork of a large forest tree, typically from 12 to 45 m (39 to 148 ft) above the ground. While the female fetches more nesting material, the male tends to be more active in nest construction. A nest built from scratch may take up to 5 months to construct, however existing nests are often repaired and re-used during successive breeding seasons, a process that can take as much as 3 months. It is typical for an eagle pair to use a nest for more than five years and, unlike several other booted eagles, crowned eagle pairs rarely build more than one nest for alternate use. Most large eagles build a very large nest and the crowned eagle is no exception, as it builds one of the largest nests of any eagle. In the first year they build a nest, it may measure 1.5 m (4.9 ft) across and 50 cm (20 in) deep. However, a larger nest, usually after several years of usage, may measure up to 2.5 m (8.2 ft) across and up to 3 m (9.8 ft) deep. The nest may consist of both dead and greener branches and have a light coverage of leaves and animal matter. Copulation takes place in the nest, several times a day.

In South Africa, the crowned eagle lays its eggs from September to October; in Rhodesia, it lays from May to October; mainly near October around the Congo River; anywhere from June to November in Kenya, with a peak in August through October; in Uganda from December to July; and in West Africa, laying peaks in October.

The clutch of the crowned eagle either contains 1 or 2 eggs. Eggs are usually just white, though may sometimes be overlaid with sparse red-brown markings. Incubation lasts for approximately 49 days. 80-90% of egg incubation is done by the female during the day. Food is mainly brought to the nest by the male in the early stages of breeding, though sometimes both sexes may deliver food. Male brings food to the incubating female every 3 to 5 days. When they initially hatch, the young tend to be quite quiet. If two eggs are laid, the younger one dies by starvation after being out-competed for food by the older one or even directly killed by its older sibling. No nest of wild crowned eagles has been known to successfully produce more than one fledgling, though in captivity two have been known to survive with human interference (supplemental feeding the chick or taking it out of the nest).

Cool Facts: Mature crowned eagles are reportedly nearly fearless towards humans and, unless shy from prior interactions, unusually prone to treat humans aggressively. Some biologists consider this species highly intelligent, cautious, independent and inquisitive when compared to other accipitrids. In falconry, crowned eagles cannot be induced to direct their hunting instinct towards large prey by increasing their hunger, as is done with Aquila eagles. Amongst post-fledging eagles in a semi-captive state, it has been noted that they border on helpless in terms of feeding and defending themselves compared to other accipitrids and are even described as “cowardly”, unwilling to even simulate attacking prey until many months after fledging. This implies a learning element occurs in wild crowned eagles during their exceptionally long post-fledging period. Crowned eagles are reportedly variable in temperament as individuals to a degree greater than that found in most other raptors.


This 3D model is found in Songbird ReMix Birds of Prey Volume IV: Eagles of the World

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