Stephanoaetus coronatus

The crowned eagle, also known as the African crowned eagle or the crowned hawk-eagle (Stephanoaetus coronatus) is a large bird of prey found in sub-Saharan Africa; in Southern Africa it is restricted to eastern areas. Its preferred habitats are principally riparian woodlands and various forests. The crowned eagle is the only extant member of the genus Stephanoaetus. A second species, the Malagasy crowned eagle (Stephanoaetus mahery) became extinct after humans settled on Madagascar. At least 90 per cent of the diet is mammalian; the usual prey taken by populations 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 barely taken. Although the crowned eagle's long tail imparts an overall length up to 90 cm (35 in), it is somewhat less massive and has a considerably shorter wingspan than Africa's largest eagle, the martial eagle (Polemaetus bellicosus). It is nevertheless considered Africa's most powerful eagle when measured in terms of the weight of its prey items. It often preys on mammals such as bushbuck (Tragelaphus scriptus), exceptionally weighing up to 30 kg (66 lb) albeit usually much less. The crowned eagle possesses unusually large talons and strong legs, and may kill by crushing the skull. The eagle is also ferocious; some records from beneath a nest show the remains of a large, male Sooty mangabey weighing 11 kg (24 lb). Due to their ecological similarities, the crowned eagle is Africa's best analogue of the harpy eagle (Harpia harpyja). Thanks to its bold and highly conspicuous behavior, it is exceptionally well-studied for a large, forest-dwelling eagle. Due to a relatively high level of habitat adaptability, it was until recently considered to be faring well by the standards of large, forest-dependent raptors. However, today it is generally thought that it is decreasing far more than was previously perceived due to the almost epidemic destruction of native tropical African forest. It is now listed by the IUCN as Near Threatened. This species was first described by Carl Linnaeus in the 12th edition of Systema Naturae, published in 1766, as Falco coronatus. Since birds were grouped largely on superficial characteristics at that time, many unrelated species were grouped by Linnaeus in the genus Falco. The actual taxonomic alignment of the crowned eagle is apparent due to its feathering over its tarsus, which is generally rare in unrelated accipitrids. The crowned eagle is actually part of the diverse 'booted eagle' group, which has sometimes been considered a distinct subfamily (Aquilinae). Included in this grouping are the genus Aquila and all species described as 'hawk eagles' including the genera Spizaetus and Nisaetus. Other assorted monotypical genera included amongst 'booted eagles' are Lophaetus, Polemaetus, Lophotriorchis and Ictinaetus. At one time, the genus Stephanoaetus was considered a 'specialized offshoot' of the Spizaetus hawk-eagles based on morphological attributes. DNA sequences utilizing one mitochondrial and three nuclear genes indicated the crowned eagle is a sister species to the Asian hawk-eagles, which are now considered a separate genus, Nisaetus, that are not closely related to the neotropical hawk-eagles, which are retained in Spizaetus. However, another recent study, this time of sequences of two mitochondrial and one nuclear genes, did not reveal a close relationship of this eagle to any other accipitrid, including the Nisaetus species, and the genus was found to be genetically highly divergent from other 'booted' eagles'. In a case of convergent evolution, the much heavier harpy eagle, which is outside of the 'booted eagle' group, has a similar skeletal morphology to the crowned eagle. Two less well-known, probably distantly related species, the mountain hawk-eagle (Nisaetus nipalensis) and the black-and-chestnut eagle (Spizaetus isidori), have also been found comparable to the crowned eagle. While both are slimmer and smaller, these eagles are also large-bodied, strong-footed offshoots of the evolutionary radiation of forest-dwelling booted eagles, respectively distributed in East Asia and South America. The adult crowned eagle even has somewhat intermediate appearance between these birds, sharing the variable patterning of the mountain hawk-eagle and some of the colouring of the black-and-chestnut. Until possibly up to 1500, another crowned eagle species, the Malagasy crowned eagle (S. mahery) existed. Similar in size and form to the extant crowned eagle, the Malagasy crowned eagle probably filled a similar niche in Madagascar, but was likely to have preyed on lemurs in place of monkeys. Apparently, the Malagasy crowned eagle became extinct due mainly to the loss of prey and habitat change, attributable to early humans on the island. To date, the living crowned eagle has no recognized subspecies. However, Simon Thomsett noted from field experience possible racial differences between crowned eagles in limited woodland habitats in East and South Africa (called by him the 'bush eagles'), which have historically been the main populations studied, and those that live in denser West African rainforest, in the central part of the species distribution. The latter population, he noted, appeared smaller but relatively larger footed, seemed chestier in build and appeared to have deeper eyebrows than the bush eagle; behaviorally the rainforest eagles seemed bolder and louder, which is reinforced in other accounts of the species. The crowned eagle is a very large eagle. Measuring from 80 to 99 cm (31 to 39 in) in length, it is the fifth longest extant eagle in the world. The female, at a weight of 3.2–4.7 kg (7 lb 1 oz–10 lb 6 oz), is around 10–15% larger than the male, at a weight of 2.55–4.12 kg (5 lb 10 oz–9 lb 1 oz). An average body mass of 3.64 kg (8.0 lb) was given in one account. Elsewhere, an average of 3.8 kg (8.4 lb) has been claimed. Overall, they are the 9th heaviest living eagle species. The wingspan typically ranges from 1.51 to 1.81 m (4 ft 11 in to 5 ft 11 in). The largest authenticated wingspan for a female was 1.9 m (6 ft 3 in), with a claim of wingspans of up to 2 m (6 ft 7 in) needing confirmation. This eagle's wingspan is quite short for the bird's size, being around the same mean width as that of a tawny eagle (Aquila rapax) or a short-toed snake eagle (Circaetus gallicus), species that weigh about half as much as a crowned eagle. However, the somewhat boxy and rounded wings are quite broad, being broader than, for example, the much longer-winged golden eagle (Aquila chrysaetos). The wing morphology of the species gives it maneuverability in its densely wooded environment. The wing chord measures 44.5–53.2 cm (17.5–20.9 in), with a median of 46.7 cm (18.4 in) in males and 51.2 cm (20.2 in) in females. While it, on average, is less heavy and has a smaller wingspan than the often sympatric martial eagle, its average total length exceeds that of the martial eagle thanks to its much longer tail. The crowned eagle's tail is from 30 to 41 cm (12 to 16 in) long, with a median of 31.5 cm (12.4 in) in males and 34.8 cm (13.7 in) in females. The bill is of a medium size relative to its body size, with one large museum specimen's bill measuring 5.5 cm (2.2 in) in length from the gape, 4.5 cm (1.8 in) in culmen length and 3.3 cm (1.3 in) in bill depth. The tarsus is of a modest length for a raptor of its size, at 8.5–10.3 cm (3.3–4.1 in), and is clearly shorter than that of martial eagle. However, the feet and legs are visibly thicker and heavier than those of the martial eagle and the talons are apparently quite massive in both length and width. While no comprehensive measurements of the talon size of wild crowned eagles are known, one female museum specimen reportedly had a hallux-claw (or hind claw, which is the largest talon on accipitrids) of 6.2 cm (2.4 in), while another female was measured at 5 years of age, the age of sexual maturity, 5.74 cm (2.26 in) in the hallux-claw and an adult male measured 4.9 cm (1.9 in). These figures put their talon size as around the same size as the largest golden eagles and close to those of a mid-sized harpy eagle. Some captive crowned eagles have been credited with a hallux-claw length of up to 10 cm (3.9 in), although, much like a single report of captive harpy eagles with a 13 cm (5.1 in) hallux-claw, no such outsized talons are known to have been confirmed. In a small sampling of large, forest-dwelling raptors, the front-left talon of the crowned eagle, at 4.74 cm (1.87 in), was around one cm less than that of a harpy eagle or the huge, recently extinct Haast's eagle (Harpagornis moorei) and slightly smaller than those of the Philippine eagle (Pithecophaga jefferyi). Considering a big female of these species can weigh up to twice as much as an average crowned eagle may illustrate the relative largeness of the crowned eagle's talons.