Aigle martial

Identification

The martial eagle is a very large eagle. In total length, it can range from 78 to 96 cm (31 to 38 in), with an average of approximately 85.5 cm (33.7 in). Its total length – in comparison to its wingspan – is restricted by its relatively short tail. Nonetheless, it appears to be the sixth or seventh longest extant eagle species. The wingspan of martial eagles can range from 188 to 240 cm (6 ft 2 in to 7 ft 10 in). Wingspans of as much as 260 cm (8 ft 6 in) have been reported but may be unsubstantiated. Average wingspans have been claimed of 205 cm (6 ft 9 in) and 207.5 cm (6 ft 10 in) for the species, however ten measured martial eagles in the wild were found to average 211.9 cm (6 ft 11 in) in wingspan. Thus, the martial eagle appears to average fourth in wingspan among living eagles, behind only the Steller's sea-eagle (Haliaeetus pelagicus), the white-tailed eagle (Haliaeetus albicilla) and the wedge-tailed eagle (Aquila audax), in roughly that order. For a species that is fairly homogeneous in its genetic make-up, the body mass of martial eagles is surprisingly variable. To some extent, the variation of body masses in the species is attributable to considerable reverse sexual dimorphism as well as varying environmental conditions of various eagle populations. Unsexed martial eagles from various studies have been found to have weighed an average of 3.93 kg (8.7 lb) in 17 birds, 3.97 kg (8.8 lb) in 20 birds and 4.23 kg (9.3 lb) in 20 birds while the average weight of martial eagles shot by game wardens in the early 20th century in South Africa was listed as 4.71 kg (10.4 lb). In weight range, the martial eagle broadly overlaps in size with the golden eagle (Aquila chrysaetos) and Verreaux's eagle (and is even exceeded by them in maximum known body mass). Based on numerous studies, the martial eagle appear to average mildly heavier than the Verreaux's eagle but (derived from the globally combined body mass of its various races), the mean body masses of golden and martial eagles are identical at approximately 4.17 kg (9.2 lb). This renders the golden and martial eagles as tied as the largest African eagles (by body mass but not in total length or wingspan, in which the martial bests the golden), as well as the heaviest two species of booted eagle in the world and as tied as the sixth heaviest eagles in the world, after the three largest species of sea eagle (Steller's being the heaviest extant, the others ranking 4th and 5th), the harpy eagle (Harpia harpyja) and the Philippine eagle (Pithecophaga jefferyi). The longest African eagle (and second longest booted eagle after the wedge-tailed eagle (Aquila audax)) is the crowned eagle by virtue of its relatively longer tail, as its body weight is slightly less than these three heaviest booted eagle species.<p>Martial eagles are highly sexually dimorphic. While females average about 10% larger in linear dimension, in body mass, the sexual dimorphism of martial eagles is more pronounced. Males reportedly can weigh from 2.2 to 3.8 kg (4.9 to 8.4 lb). Seven males in southern Africa averaged 3.17 kg (7.0 lb) and five in another dataset averaged 3.3 kg (7.3 lb). Twelve adult males in Maasai Mara, Kenya averaged 3.45 kg (7.6 lb). Meanwhile, females can weigh from 4.45 to 6.5 kg (9.8 to 14.3 lb). In southern Africa, seven females averaging 4.95 kg (10.9 lb). Elsewhere, a claim was made of an average of 5.2 kg (11 lb) almost certainly describes a sample entirely of female specimens. In the Maasai Mara, 7 females averaged 4.67 kg (10.3 lb). Reports of males weighing as much as 5.1 kg (11 lb) and females weighing as little as 3.9 kg (8.6 lb) are known but may possibly represent individual eagles misidentified by sex, which is reportedly not infrequent due to mistakes in the field. Thus the dimorphism by weight is roughly 36% in favor of the female, which is unusually out-of-sync with the linear differences between the sexes. For example, the greater spotted eagle (Clanga clanga), the most sexually dimorphic booted eagle overall with a linear difference between the sexes of 20%, has around the same level of sexual dimorphism by body mass as the martial eagle which show about half as much linear dimorphism. In standard measurements, male martial eagles measure 560 to 610 mm (22 to 24 in) in wing chord size, 273 to 280 mm (10.7 to 11.0 in) in tail length and 97 to 118 mm (3.8 to 4.6 in) in tarsus length. Meanwhile, females measure 605 to 675 mm (23.8 to 26.6 in) in wing chord, 280 to 320 mm (11 to 13 in) in tail length and 114 to 130 mm (4.5 to 5.1 in) tarsal length. Overall, the bulk and much more massive proportions of females, which include more robust feet and longer tarsi, may at times allow experienced observers to sex lone birds in the wild.<p>The adult's plumage consists of dark brown coloration on the upperparts, head and upper chest, with an occasional slightly lighter edging to these feathers. The dark feathers can appear grayish, blackish or even plum-colored depending on lighting conditions. The body underparts are feathered white with sparse but conspicuous blackish-brown spotting. The underwing coverts are dark brown, with the remiges being pale streaked with black, overall imparting the wings of adults a dark look. The underside of the tail has similar barring as the remiges while the upperside is the same uniform brown as the back and upperwing coverts. The eyes of mature martial eagles are rich yellow, while the cere and large feet pale greenish and the talons black. Martial eagles have a short erectile crest, which is typically neither prominent nor flared (unlike that of the crowned eagle) and generally appears as an angular back to a seemingly flat head. This species often perches in a quite upright position, with its long wings completely covering the tail, causing it be described as "standing" rather than "sitting" on a branch when perched. In flight, martial eagles bear long broad wings with relatively narrow rounded tips that can appear pointed at times depending on how the eagle is holding its wings. It is capable of flexible beats with gliding on flattish wings, or slightly raised in a dihedral. This species often spends a large portion of the day on the wing, more so than probably any other African eagles, and often at a great height. Juvenile martial eagles are conspicuously distinct in plumage with a pearly gray colour above with considerable white edging, as well as a speckled grey effect on crown and hind neck. The entire underside is conspicuously white. The wing coverts of juveniles are mottled grey-brown and white, with patterns of bars on primaries and tail that are similar to adult but lighter and greyer. In the fourth or fifth years, a very gradual increase to brownish feather speckling is noted but the back and crown remain a fairly pale grey. At this age, there may be increasing spots on throat and chest which coalesce into a gorget and some spots on abdomen may variably manifest as well. The eyes of juveniles are dark brown. This species reaches adult plumage by its seventh year with the transition to adult plumage happening quite rapidly after many years in a little-changing juvenile plumage.<p>There are a few serious identification challenges for the species. The black-chested snake eagle (Circaetus pectoralis) is similar in overall colouring (despite its name it is brown on the chest and the back, being no darker than the adult martial eagle) to martial eagles but is markedly smaller, with a more prominent, rounded head with large eyes, plain, spotless abdomen, bare and whitish legs. In flight, the profile of the snake eagle is quite different, with nearly white (rather than dark brown) flight feathers and much smaller, narrower wings and a relatively larger tail. For juveniles, the main source for potential confusion is the juvenile crowned eagle, which also regularly perches in an erect position. The proportions of crowned eagles are quite distinct from martial eagles as they have much shorter wings and a distinctly longer tail. The juvenile crowned eagle has a whiter head, more scaled back, and spotted thighs and legs lacking in the martial eagle. Beyond their distinct flight profile by wing and tail proportions, crowned eagles have whiter and more obviously banded flight-feathers and tail. Other large immature eagles in Africa tend to be much darker and more heavily marked both above and below than martial eagles.<p>Martial eagles have been noted as remarkable for their extremely keen eyesight (3.0–3.6 times human acuity), partly due to their eye being nearly as large as a human's eye. Due to this power, they can spot potential prey from a great distance, having been known to be able to spot prey from as far as 5 to 6 km (3.1 to 3.7 mi) away. Their visual acuity may rival some eagles from the genus Aquila and some of the larger falcons as the greatest of all diurnal raptors. The talons of martial eagles are impressive and can approach the size, especially in mature females, of those of the crowned eagle despite their slenderer metatarsus and toes compared to the crowned species. Accipitrids usually kill their prey with an elongated, sharp hind toe claw, which is referred to as the hallux claw and is reliably the largest talon in members of the accipitrid family. The average length of the hallux claw in unsexed martial eagles from Tsavo East National Park, Kenya was found to be 51.1 mm (2.01 in). In comparison, the average hallux claw of a large sample of golden eagles was similar at 51.7 mm (2.04 in). Meanwhile, the three largest clawed modern eagles were found to measure as such: in small samples, the Philippine eagle and crowned eagle had an average hallux claw length of 55.7 mm (2.19 in) and 55.8 mm (2.20 in), respectively, and harpy eagles have an average hallux claw length of approximately 63.3 mm (2.49 in). A further sample of martial eagles averaged 47.4 mm (1.87 in) in 6 males and 56.2 mm (2.21 in) in 7 females, with the median between the sexes being 52.3 mm (2.06 in), these being the largest talons of all booted eagles behind only the crowned eagle. The inner claw on the front of the foot of the martial eagle is especially sizeable proportional to other extremities and unusually can approach, if not reach, the same size as the hallux claw. This inner claw was found to average 46.1 mm (1.81 in), in comparison to that of the crowned eagle which measures 47.4 mm (1.87 in). The tarsus is quite long in martial eagles, the fourth longest of any living eagle and the longest of any booted eagle species, seemingly an adaptation to prey capture in long grass, including potentially dangerous prey. The bill is of medium size relative to that of other large eagles, with a mean culmen length from Tsavo East of 43.7 mm (1.72 in). The bill is larger than the average bill of the large members of the genus Aquila but is notably smaller than those of the large species of sea eagle and the Philippine eagle. The gape size of martial eagles is relatively large, however, being proportionally larger than in other booted eagle species behind (albeit considerably behind) the Indian spotted eagle (Clanga hastata) and the steppe eagle (Aquila nipalensis) in relative gape size, indicating a relative specialization towards swallowing large prey whole.<p>The martial eagle is a weak and infrequent vocaliser. Little vocal activity has been reported even during the breeding season. The recorded contact call between pair-members consists of the birds, usually when perched, letting out a low mellow whistle, ko-wee-oh. More or less the same vocalisation is known to have been uttered by females when male brings food and repeated mildly by large begging young. During territorial aerial display and sometimes when perched, adults may utter a loud, trilling klee-klee-klooeee-klooeee-kulee. The territorial call may be heard from some distance. Recent fledglings also at times make this call. A soft quolp may be heard, made by pairs around their nest, perhaps being a mutual contact call. In comparison, the crowned eagle is highly vocal especially in the context of breeding.

Taxonomie

The Accipitridae family (hereafter accipitrids) is by far the most diverse family of diurnal raptors in the world, with more than 230 currently accepted species. As a member of the booted eagle subfamily, Aquilinae, the martial eagle is one of the roughly 15% of extant species in the family to have feathers covering its legs. This helps distinguish these species from other eagles and raptors, as they are present even in tropical species such as the martial eagle. Under current classifications, booted eagles consist of approximately 38 living species that are distributed in every continent inhabited by the accipitrids, which excludes only the continent of Antarctica. Just under half of the living species of booted eagle are found in Africa. Studies have been conducted on the mitochondrial DNA of most booted eagle species, including the martial eagle, to gain insight on how the subfamily is ordered and which species bear relation to one another. DNA testing in the 1980s indicated the martial eagle was a specialized off-shoot of the small-bodied Hieraaetus eagles, and one study went so far as to advocate that the martial eagle be included in the genus. However, more modern and comprehensive genetic testing has shown that the martial eagle is distinct from other living booted eagles and diverged from other extant genera several million years ago. Genetically, the martial eagle fell between two other species in monotypical genera, the African long-crested eagle (Lophaetus occipitalis) and the Asian rufous-bellied eagle (Lophotriorchis kienerii), that similarly diverged long ago from other modern species. Given the disparity of this species' unique morphology and that the two aforementioned most closely related living species are only about as large as the bigger buzzards, the unique heritage of the martial eagle is evident. <p>There are no subspecies of martial eagle, and the species varies little in appearance and genetic diversity across its distribution.

Nom scientifique

Polemaetus bellicosus

Autorité

(Daudin, 1800)

Ordre

Accipitriformes

Famille

Accipitridés

Genre

Polemaetus

Répartition et habitat

The martial eagle is to some degree adaptable to varied habitats but shows an overall preference for open woods and woodland edges, wooded savannah and thornbush habitats. The martial eagle has been recorded at elevations of up to 3,000 m (9,800 ft) but is not a true mountain dwelling species and resident eagles do not usually exceed an elevation of 1,500 m (4,900 ft). These eagles also avoid closed-canopy forests and hyper-arid desert. As such it is mostly absent from Guinean and Congolian forests, despite the species' requirement for large trees for nesting purposes. It is shown that martial eagles can inhabit forests locally in areas where openings occur. For example, in a bird atlas for the country of Kenya, perhaps surprisingly, 88% of martial eagles were found to reside in well-wooded areas and they occurred in areas where annual rainfall exceeded 250 mm (9.8 in). In southern Africa, they have adapted to seemingly more open habitats than elsewhere in their range, such as semi-desert and open savanna with scattered trees, wooded hillocks and, as a recent adaptation, around pylons. In the desert areas of Namibia, they utilize ephemeral rivers that flow occasionally and allow large trees to grow. They usually seem to prefer desolate or protected areas. In the Karoo of South Africa, they consistently avoid areas with moderate to heavy cultivation or with heavier or more consistent winter rainfall. One study on the occurrence of diurnal raptors in protected areas against unprotected areas found that martial eagle detection was nearly twice as frequent in protected areas during the dry season and more than three times as frequent during the wet season than in unprotected areas. The martial eagle can be found in most of sub-Saharan Africa, wherever food is abundant and the environment favourable. With a total estimated distribution of about 26,000 km2 (10,000 sq mi), it has a substantial distribution across Africa, giving it a somewhat broader range than other species there like the crowned eagle (Stephanoaetus coronatus) and the Verreaux's eagle (Aquila verreauxii). Although never common, greater population densities do exist in southern Africa and in some parts of east Africa. Martial eagles tend to be rare and irregular in west Africa but are known to reside in Senegal, The Gambia and northern Guinea-Bissau, southern Mali and the northern portions of Ivory Coast and Ghana. From southern Niger and eastern Nigeria the species is distributed spottily through Chad, Sudan and the Central African Republic as well as the northern, eastern, and southern portions of the Democratic Republic of the Congo. In east Africa, they range from Somaliland and Ethiopia more or less continuously south through Kenya, Uganda, Tanzania and in southern Africa from Angola, Zambia, Malawi and southern Mozambique to South Africa. Some of the larger remaining populations are known to persist in Zimbabwe and South Africa. Generally, these birds are more abundant in protected areas such as Kruger National Park and Kgalagadi Transfrontier Park in South Africa, or Etosha National Park in Namibia.

Migration

Resident species

Comportement

The martial eagle spends an exceptional amount of the time in the air, often soaring about hill slopes high enough that binoculars are often needed to perceive them. When not breeding, both mature eagles from a breeding pair may be found roosting on their own in some prominent tree up to several miles from their nesting haunt, probably hunting for several days in one area, until viable prey resources are exhausted, and then moving on to another area. However, martial eagles, especially adult birds, are typically devoted to less disturbed areas, both due to these typically offering more extensive prey selection and their apparent dislike for a considerable human presence. Martial eagles tend to be very solitary and are not known to tolerate others of the own species in the area outside of the pair during the breeding season. In general this species is more shy towards humans than other big eagles of Africa, but may be seen passing over populated country at times. The most frequently seen type of martial eagle away from traditional habitats are presumed nomadic subadults. One individual that was ringed as subadult was recovered 5.5 years later 130 km (81 mi) away from the initial banding site. Another martial eagle ringed as a nestling was found to have moved 180 km (110 mi) in 11 months.

Conservation

Tendance de la population

declining