Bateleur

Identification

The bateleur is of note for its unique morphology and plumage, with some anatomical similarities to both snake eagles and vultures. The species has a thick neck and a very large, rather conspicuously cowled head with a proportionately short bill, albeit one covered with a very large cere. The cowl is also present on snake eagles but in those it is less dramatically apparent. The other features in perched adult bateleurs are rather oddly stumpy, such as the short legs and exceptionally short tail, possibly the shortest proportionately of all raptors. Its posture while perched is extremely upright, making them look like quite a tall raptor on the ground despite its rather short legs. Even while perched, the body tends to be dominated by their exceptionally large wings, which possess some 25 secondary feathers, perhaps more than any other raptor. The adult bateleur usually has a chestnut coloration along the mantle, back, rump and tail, including the undertail coverts. The adult male bateleur is predominantly black with grey shoulders, which appear edged with white when freshly moulted. The adult female differs by having grey-brown, not black, on the greater coverts and black-tipped grey, not black, secondaries. Furthermore up to 7% of adults have a "cream morph" where they have chestnut tails but the other chestnut areas are almost fully replaced by cream to pale brown coloring. The cream morph may reportedly be slightly more prevalent in drier areas. The bare parts of adult bateleurs are exceptionally conspicuous, with the adult cere, bare facial skin and feet all being rather bright red, however in some they can also temporarily fade to pink, pale pink or yellowish at times, such as when they are perching in the shade or bathing. The bare parts flush the most red during times of excitement. The bill itself is black with a yellow centre and red base. The eyes are dark brown.<p>The juvenile is very distinct from the adults of the species. Juveniles of the bateleur have a longer tail than mature birds. They furthermore have essentially all brown coloring, with dull rufous to creamy edging apparent on some areas. The head of the juvenile bateleur is paler and tawnier than elsewhere on its body while the eyes are brown, the cere a rather unique greenish-blue and the feet whitish in colour. At as late as 2–3 years of age, the immature bateleur is still much the same in appearance as the juvenile but by the fourth year becomes more sooty-brown, with sexual dimorphism already evidenced by the more extensive dark wing markings of males. In the 5th year, the plumage may show the first signs of chestnut and the grey colour about back and shoulders tend to manifest. Also from 3–5 years old, the cere and feet turn yellow then to dull-pink. By the sixth and seventh years of life, the plumage of subadult bateleurs blackens and the chestnut portions of the plumage increase. The shoulders become fully grey by the 8th year, the likely age of maturity. As for the bare parts in juvenile bateleurs, the cere and facial skin are a distinct pale grey-blue to green-blue. The juvenile's feet are greenish-white to greyish-white, at 4-5 the cere, facial skin and feet turn yellow, then pink before finally reddening. The eyes are similar in hue to those of adult bateleurs but are a slightly lighter, being more honey-brown, while the bill of juveniles are mainly pale grey-blue in colour.<p>In flight, the bateleur appears as a rather large raptor with disproportionately elongated, rather narrow and slightly bow-shaped wings, which appear pinched in at the bases, broad across the secondaries and regularly narrow, pointed and upturned at the tips. Upon sighting, the wings often catch the eye before the large head, which is proportionately slightly bigger even than their cousins, the snake eagles. The tail is so short in adult bateleurs that the feet extend below the tail tip, almost giving the impression that the raptor nearly has no tail. This is as opposed to juveniles, where the feet come up about 5 cm (2.0 in) short of the tail tip, with the feet coming to exceed the tail, which is shrinking via moults, in length around the 5th year of maturation. The adult bateleur's wingspan is an extraordinary 2.9 times greater than its total length. The adult male bateleur is mostly black above with a chestnut back and tail and grey forewings, below he is black on the body, contrasting with a chestnut tail, as well as with the white wing linings and black flight feathers except for the greyish based primaries. The adult female bateleur is similar in plumage to the male overall but differs in her black-tipped grey secondaries above and more extensively white underwings with the black on the female confined to the wingtips and trailing edges. The juvenile bateleur on the wing appears broader winged and especially longer tailed with a largely uniform brown coloration, including the greater coverts, with paler feather mainly about the head as well as on the flight feathers.<p>The bateleur is a mid-sized eagle and large raptor. It is likely the second heaviest of the Circaetinae subfamily of accipitrids. By far the largest of the subfamily is the Philippine eagle which is more than twice as massive and is far larger in all aspects of measurement than the bateleur, with a drastically differing structure (broad, relatively short wings, very long legs and tail). One traditional snake eagle, the brown snake eagle ( Circaetus cinereus), rivals the bateleur in most aspects of size including body mass but possesses a rather longer tail and slightly shorter but broader wings. Additionally, the widespread and slightly broader-winged short-toed snake eagle and proportionately long and slender-winged black-breasted snake eagle (Circaetus pectoralis) can be nearly as large in wingspan as the bateleur but tend to be somewhat less heavy. The total length of the bateleur is 55 to 70 cm (22 to 28 in). Typical length of a full-grown bird is around 63.5 cm (25.0 in). The wingspan of bateleurs can vary from 168 to 190 cm (5 ft 6 in to 6 ft 3 in). Body mass of bateleurs can vary from 1,800 to 3,000 g (4.0 to 6.6 lb). One sample of 10 unsexed bateleurs weighed an average of 2,200 g (4.9 lb) while a smaller sample of three weighed an average of 2,392 g (5.273 lb). Additionally, a median body mass of 2,385 g (5.258 lb) was cited in one study.<p>The bateleur evidences some sexual dimorphism in favour of the female as is expected in raptorial birds but this size difference is fairly minimal relative to many other accipitrids, averaging up to about 6%. Among standard measurements, males have a wing chord length of 476 to 553 mm (18.7 to 21.8 in) while that of the female is 530 to 559 mm (20.9 to 22.0 in). In tail length, adult males measure 98 to 124 mm (3.9 to 4.9 in) and can be even shorter in adult females at 105 to 113 mm (4.1 to 4.4 in), in some cases the adult's tail may reportedly measure as short as 72 mm (2.8 in). This contrasts with the tail of juvenile bateleurs which measures 142 to 172 mm (5.6 to 6.8 in). The tarsus can measure from 67 to 75 mm (2.6 to 3.0 in) in males and 72 to 75 mm (2.8 to 3.0 in) in females. Unsexed adult bateleurs in Tsavo East National Park were found to average 513 mm (20.2 in) in wing chord length, 34.5 mm (1.36 in) with a range of 28.6 to 38 mm (1.13 to 1.50 in) in culmen length and a relatively small hind claw length of 30.6 mm (1.20 in). While the hind or hallux claw is usually the most enlarged in most species of accipitrid, on the other hand in the Tsavo East bateleurs, unusually the middle claw on the front of the foot was slightly larger at 32 mm (1.3 in). Notably the proportions of bateleurs are similar to snake eagles with robust feet with rough, thick skin and short talons, the bateleur in particular having very thick, large toes structurally almost like those of a big owl and very sharp talons reminiscent in sharpness of highly predaceous larger African raptors. Further like snake eagles, bateleurs have a rather large headed but with a smallish beak coupled with a large gape. These adaptations generally equip the subfamily to better handle and ingest snakes relative to other accipitrids.<p>The bateleur, particularly in its adult plumage, is often considered one of the most distinctive raptors in the world. When perched or flying adults or older immatures are quite unmistakable. The bateleur can be readily be distinguished even by inexperienced observers from the very differently-shaped and usually rather smaller-bodied and winged augur buzzards (Buteo augur) and jackal buzzards (Buteo rufofuscus). These do not overlap with bateleurs in nearly all respects of morphology, proportions nor flight actions. Nonetheless, both of these buzzards are sometimes mistaken for bateleurs due to their own combinations of black, white and chestnut, which are completely differently composed than those of the bateleur. Despite how distinctive the buzzards are from the bateleur, some reports of bateleurs from areas where they are currently gone are almost certain to have been misidentified jackal buzzards. Juveniles and immatures of up to 2–3 years old are hardly less distinctive in shape but could be confused, largely due to similar proportions of their large head, brown plumage and whitish legs with certain snake eagles. The brown snake eagle is perhaps the most similar to the juvenile bateleur but it has yellow eyes, longer legs, much broader, shorter and differently shaped wings with the tips of wings reaching its banded tail. Even the black-chested and the rather slight Beaudouin's snake eagle (Circaetus beaudouinii) are sometimes considered potentially confusable with juvenile bateleurs, but both of these respective species are rather uniform and darker brown ventrally and about the head and much paler dorsally, with a highly different contrasting whitish cream colour below.<p>Bateleurs are usually silent for much of the year. The main call, uttered whether perched or in aerial display, or when pirating from other raptors, is a far-carrying, loud raucous schaaaa-aw. They may too vocalize in a similar manner during courtship. Alternatively, bateleur calls may consist of resonant barking calls, kow-aw. The barking call can be accompanied by half-spread wings and jerking of the body up and down or may too be uttered in flight, the latter in a similar manner to that of a fish eagle. Distraction display are sometimes accompanied by subdued barking chatter, ka-ka-ka-ka.... A not dissimilar call of kau-kau-kau-koaagh-koaggh has been described as given by perched birds. Other softer calls are uttered when perched near the nest. The young of the bateleur tend to engage harsh squealing call is kyup-kyup keeaw keeaw, usually as a hunger call at approach of parent with food. Also the species' young may make a melodious twip call.

Taxonomy

The bateleur has been found to be a proper member of the subfamily Circaetinae, commonly called snake or serpent eagles, via a variety of genetic studies. Given the outward similarities of the bateleur to snake eagles, the relationship has long been inferred by authors. In particular, the bateleur was suggested to have their closest living relations in the similarly large Circaetus snake eagles. This relationship was well borne-out by a genetic study that found that this species and the short-toed snake eagle (Circaetus gallicus) form a monophyletic clade, based on nucleotide sequences in the cytochrome b gene. Even though, when contrasted with snake eagles, bateleurs appear to differ greatly in plumage patterns, the two genera show certain similarities in food, feeding behavior, and breeding biology. However, Lerner and Mindell (2005), based on the molecular sequence from two mitochondrial genes and one nuclear intron, indicated a previously unsuspected close relationship of the bateleur with similarly "aberrant" but extremely different, in nearly every respect of appearance and life history, member of the Circaetinae, the Philippine eagle (Pithecophaga jefferyi). Chromosome banding studies have also found a relatively recent genetic relationship of the bateleurs with the Old World vultures.<p>The common name of "Bateleur" is French for "street performer". Meanwhile, the scientific name is from name teras (Greek) for "marvelous"; ops (Greek) for "face"; e (Latin) for "without"; caudatus (Latin) "tail". The bird was given its common name by François Levaillant, a French naturalist and explorer. The original scientific name was Falco ecaudatus, given by François Marie Daudin, as the concept of disparate genera between birds of prey was devised later on (nor were falcons then known to be unrelated to many other variety of diurnal birds of prey).

Scientific name

Terathopius ecaudatus

Authority

(Daudin, 1800)

Order

Accipitriformes

Family

Accipitridae

Genus

Terathopius

Range and habitat

The bateleur occupies a very large range through mainly sub-Saharan Africa. The species resides in West Africa from southern Mauritania to Senegal, The Gambia, Guinea-Bissau, Guinea, the northern portions of Sierra Leone, Ivory Coast and much of Ghana through western Burkina Faso, much of Togo and Benin and northern and central Nigeria. It is possibly extinct in Mauritania, range restricted in Guinea (mainly to Kiang West) and Liberia but is still locally common where good habitat remains elsewhere in this region. Similarly far north, a rare population is believed to persist out of Africa in extreme southwestern Saudi Arabia and western Yemen. In central and east Africa, the bateleur may be found in northern Cameroon, southern Niger, southern Chad, southern Sudan, South Sudan, northern Central African Republic, Eritrea, Ethiopia, Djibouti, western Somalia, northern, eastern and southern Democratic Republic of the Congo and a majority of Uganda, Kenya and Tanzania. In Southern Africa, the bateleur is found quite widely, being found almost throughout, where habitat is favorable, Angola, Zambia, Zimbabwe, Malawi and Mozambique. Additionally, they may range Botswana in all but southernmost portion also being found still in northern and eastern Namibia and northwestern South Africa, where its range has contracted considerably from as far south once as the Cape Province to almost entirely to being found exclusively within protected areas north of the Orange River excepting a portion of Kruger National Park. The species is possibly extirpated from Eswatini in southern Africa. The bateleur is regarded as a vagrant in the countries of Tunisia, Cyprus and rarely Egypt, Israel and Iraq. In April 2012 a juvenile bateleur was seen in Algeciras in southern Spain. In 2015 and 2022, juveniles spotted as far north as Black Sea coast of Turkey in the cities of Istanbul and Sinop respectively.<p>The bateleur is a common to fairly common resident or nomadic bird of the partially open savanna country and of woodland within Sub-Saharan Africa. During breeding, it tends to require closed-canopy savannah-woodland habitats, including Acacia savanna as well as mopane and miombo woodlands. They may too acclimate to thornveld and overall various fairly shrubby areas. It tends to rarely occur in heavily forested and mountainous habitats. However, while the species can forage extensively in largely treeless habitats such as treeless savanna but is nearly as rare in pure desert lacking arborescent growth as it is in tropical rainforests. Bateleurs are seldom to be found around extensive wetlands but may regularly be found near watering holes. Although often in fairly dry savanna habitats, in Kenya it is reportedly absent from areas where the rainfall is under 250 mm (9.8 in) annually, probably because it limits the growth of the leafy trees that they require for nesting. In Ethiopia, it tends to be associated with well-wooded areas. Habitat tends to be most closely studied in southern Africa. It is mostly common found in broad-leaved woodland in the Okavango Delta in Botswana. In Namibia it is often found over tall woodland near drainage lines, and over ephemeral rivers in north-eastern Namibia and within the more arid Etosha National Park. In Zambia, it is found in a variety of habitats from woodlands to open plains but avoids the most densely wooded areas. Reportedly in Malawi, it is often associated with Forest–savanna mosaics but is sometimes regularly seen over cultivated areas and even may be seen flying over large cities. To the contrary, in Mozambique it is said to avoid areas with a dense human population. The species can occur from sea level up to 4,500 m (14,800 ft), but not normally a mountain-dwelling species and mainly occurs below 3,000 m (9,800 ft). This is supported in Zimbabwe, where the bateleur is relatively common but appears to largely avoid the extensive amount of hilly and rugged areas present in that country.

Migration

Resident species

Behavior

This bateleur is unusually conspicuous due to its propensity for gliding flights over favorable habitats in much of Africa. The bird spends a considerable amount of time on the wing, particularly in low-altitude flights. Due to the conspicuous behaviour and colorful plumage, the bateleur is frequently described in superlatives such as "one of the most beautiful and spectacular things that flies". This species tends to take off with unusually fast, shallow beats for a bird of this relative large size. After take-off, the bateleur sails at a mean speed of about 50 to 60 km/h (31 to 37 mph). They often rock from side-to-side with the wings held in a strong dihedral with very limiting flapping, vaguely recalling the flight of the American turkey vulture (Cathares aura) although the flight is generally more forceful, fast and acrobatic than that species and at times can be evocative of a huge falcon. Although the species tends to fly fairly low, bateleurs can soar and circle quite high as well. Engaged in its aforementioned dihedral flight it is often cants continuously from side-to-side, likely the origin of which it was given its common name (loosely "tumbler", "balancer" or "tightrope walker") of French derivation. Various flying embellishments may be undertaken nearly aseasonally. Although not typically given to forward somersault nor to loop-the-loop, bateleurs may with some regularity perform a rapid 360 degrees sideways roll. They are often given to flying with more embellishments when in the presence of another bateleur, even with juveniles provoking one another entirely uncoupled seemingly from breeding courtship or territorial displays. Typical home ranges of around 40 km2 (15 sq mi) were reported per pair in Kruger National Park and these were considered unusually small by overall species standards. Intruders to whom this behaviour is displayed always submit and submission is shown by retreating to a safe upper boundary (elevation). Males and females both display this behaviour in all stages of the breeding cycle. This behaviour is mainly shown to members of the same sex and particularly to non-adults, as it is thought that they may have a greater ability to take over another bird's territory (having greater competitive ability for limited food resources).<p>The bateleur is generally a solitary bird. However, juveniles may accompany one or both parents for about three months and loose congregations of as many as 40-50 or more have been record of mainly immatures. These tend to be aggregations of otherwise unassociated immature bateleurs attracted to rich feeding areas such as newly-discovered carrion, bush fires, recently burnt areas or temporary floods and occasionally by termite emergences. In the wild bateleurs are shy of man and sensitive to disturbance at the nest, easily abandoning the structure. In captivity, however, they become unusually tame. Bateleur eagles are among a group of raptors that secrete a clear, salty fluid from their nares whilst eating. According to Schmidt-Nielson's 1964 hypothesis, this is due to the general necessity for birds to use an extrarenal mechanism of salt secretion to aid water reabsorption.<p>Generally, as in most raptors found as breeding residents in Africa, the bateleur is considered sedentary and territorial but it is a species that requires very large home ranges. However, in general the species neither as staunchly residential nor sedentary as many other Sub-Saharan African raptors. Both immature and sometimes adult bateleurs are considered clearly nomadic. At times, the bateleur is even regarded as an "irruptive or local migrant". Some regular north-to-south movements may occur in West Africa and may occur transequatorially in East Africa to avoid heavy rains. In Kruger, immatures are driven out by adults on territory during the breeding season and then often wander widely before returning for the non-breeding season. Recoveries of juveniles in southern Africa show that individuals have been recovered at assorted distances from their nests of origin ranging from as far as 30 to 285 km (19 to 177 mi) away. It was noted that in some cases, heavier rainfall may have caused farther afield dispersals.<p>Bateleurs seem to devote an exceptional amount of time to thermoregulation frequently spending much of its day variously sunning, to warm up, and bathing, to cool off. These eagles are frequently seen to enter water-bodies for a bath and then open their wings to often sunbathe. Standing upright and holding their wings straight out to the sides and tipped vertically, a classic 'phoenix' pose as they turn to follow the sun. Bateleurs will stand on the ground with their wings spread, exposing the feathers to direct sunlight, warming the oils in the feathers. The bird will then spread the oils with its beak to improve its aerodynamics. In some countries, local nicknames of the species may include as the "Conifer eagle" or "Pine eagle" due to its feathers resembling a conifer cone when fluffed up and engaging in thermoregulatory behaviour. At times, this is described as a "striking heraldic posture". Bateleurs may also be seen "praying" allowing ants to crawl over the wings and feathers, collecting bits of food, dead feather and skin material. When covered in ants, the bateleur then ruffles its feathers, startling the ants, which react by secreting formic acid as self-defence. This in turn kills the ticks and fleas, possibly ridding the host of its parasites.

Conservation

Bateleurs are a wide ranging species but have shown rather strong declines. Per estimates from the 1990s, extrapolated from an average of 150 km2 (58 sq mi) per pair, it was projected that the total population could have been around 180,000 birds including young ones. However, it is likely that the species numbers far lower than that. Currently, the IUCN estimates broadly from 10,000 to 100,000 total individuals. The numbers in Southern Africa have shown the most dramatic and drastic known reductions. At one time, the species numbers at 2000-2500 pairs in the former Transvaal Province alone which was down to around 420 to 470 pairs by the 1990s. More recently it was estimated that there are less than 700 pairs in the entire region of Southern Africa, although that number may be too excessively conservative. In all the bateleur has declined by an estimated 75% in Southern Africa. The species is considered threatened in Zimbabwe, Namibia, Eswatini and South Africa and still considered not uncommon but probably declining in Malawi, Zambia, Mozambique and Botswana. Declines are not endemic to Southern Africa for bateleurs, with declines strongly detected as well in Ivory Coast and Sudan. Addition countries that have reported strongly declining numbers are in Togo, Niger and Nigeria. Where bateleurs were once common in road surveys in Central-West Africa, none were detected in newer road surveys from the 2000s in the same areas. Claims of an increase in potential numbers of bateleur in Uganda are not verified.<p>Decline of the species and the reduction in range is suspected to have been moderately rapid over the past three generations. Generally, throughout the range, the bateleur is considered much more common in protected areas. However even in several protected areas, numbers of bateleurs seem to decreasing. The declines of the species are almost entirely due to anthropogenic causes. These include but are not limited to habitat destruction, the poisoning of carcasses, persecution through shooting and possibly pesticide use. Poisoning of carcasses is a major issue for scavenging animals, especially birds like vultures, in Africa. Zambian bateleurs may suffer from deliberate poisonings as well as those in Eswatini, Botswana, Zimbabwe and Mozambique. The bateleur's wide foraging areas and their ability to locate very small pieces of carrion, makes them highly susceptible to poison-laced carcasses even from a small proportion of farmers who use poisons. Bateleurs and other eagles are not usually the direct target of these poisoning operations, which in some cases may be directed to unfavored mammals like jackals or in other cases directed towards vultures by poachers to hide their illegal wildlife killings. The decline of South African bateleurs is primarily linked with poisonings, primarily from large-scale farming operations. It is possible that bateleurs may suffer from the effects of DDT though it is found in a small sample of 3 eggs from South Africa that they evidenced low subcritical levels of DDT metabolites, probably not enough to effect overall populations. However, it is projected that pesticide use may be harming populations in Zambia as well as in Botswana. Ongoing persecution is both serious and unsustainable, beyond poisoning, such killings are known to extent to ongoing shooting and trapping. Some trapping occurs of the species for its feathers which are used in medicine by traditional healers for predicting future events Less well known but probably occurring declines may be due to flying into manmade objects including wire collisions, reservoir drownings and road-killings. Additionally, shrinking habitat has been found to be a prevalent threat to bateleurs due largely to expanding human settlements and intensifying livestock agriculture. A further effect from humans is regular disturbance at bateleur nests, although not typically as deliberate as many other threats, this is causing the breeding success rates to plummet farther. No large scale actions are underway but they are possibly protected in Yemen as an endangered species. It is proposed to implement education and awareness campaigns across its range to reduce the use of poisoned baits. Regular population monitoring is being carried out.

Population trend

declining