The bateleur (; Terathopius ecaudatus), also known as the bateleur eagle, is a medium-sized eagle in the family Accipitridae. It is often considered a relative of the snake eagles and, like them, it is classified within the subfamily Circaetinae.Kemp, A. C., G. M. Kirwan, and D. A. Christie (2020). Bateleur (Terathopius ecaudatus), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. It is the only member of the genus Terathopius and may be the origin of the "Zimbabwe Bird", the national emblem of Zimbabwe. Adult bateleurs are generally black in colour with a chestnut colour on the mantle as well as on the rump and tail. Adults also have gray patches about the leading edges of the wings (extending to the secondaries in females) with bright red on their cere and their feet. Adults also show white greater coverts, contrasting with black remiges in males, gray patches on the underwing primaries and black wingtips. The juvenile bateleur is quite different, being largely drab brown with a bit of paler feather scaling. All bateleurs have extremely large heads for their size, rather small bills, large feet, relatively short legs, long, bow-like wings and uniquely short tails, which are much smaller still on adults compared to juvenile birds.Hockey, P.A.R.; Dean, W.R.J. and Ryan, P.G. 2016. Roberts VII Birds of Southern Africa. John Voelcker Book Fund.
This species is native to broad areas of Sub-Saharan Africa and scarcely up into Arabia. It is characteristically a bird of somewhat open habitats such as savanna with some trees present and open dry woodland. It is in life history, a rather peculiar bird of prey with a free-wheeling generalist diet that includes much carrion but also tends to hunt a wide range of live prey, including many small to unexpectedly relatively large mammals and reptiles along with generally relatively small birds.Steyn, P. (1983). Birds of prey of southern Africa: Their identification and life histories. Croom Helm, Beckenham (UK). 1983. Bateleurs are highly aerial birds that spend much time soaring and will frequently fly with exaggerated embellishments, perhaps when excited or angered.Watson, R. T. (1989). Aggressive display and territoriality of the bateleur Terathopius ecaudatus. African Zoology, 24(2), 146-150. They tend to build a relatively small if sturdy stick nest in a large tree and lay only a single egg. Despite being a rather aggressive bird in other contexts, bateleurs are easily flushed from their own nest, making them exceptionally vulnerable to nest predators, including humans, and nest failures.Herholdt, J. J., Kemp, A. C., & Du Plessis, D. (1996). Aspects of the breeding status and ecology of the Bateleur and Tawny Eagle in the Kalahari Gemsbok National Park, South Africa. Ostrich, 67(3-4), 126-137. It may take as long as 7 to 8 years to attain full maturity, perhaps the longest stretch to maturity of any raptor. This species has long been known to be declining rather pronouncedly in overall population and it is mostly confined to protected areas today.Brown, L. & Amadon, D. (1986). Eagles, Hawks and Falcons of the World. The Wellfleet Press. .Thiollay, J. M. (2007). Raptor declines in West Africa: comparisons between protected, buffer and cultivated areas. Oryx, 41(3), 322-329.Garbett, R., Herremans, M., Maude, G., Reading, R. P., & Amar, A. (2018). Raptor population trends in northern Botswana: A re-survey of road transects after 20 years. Biological Conservation, 224, 87-99. Currently the IUCN classifies the bateleur as an Endangered species due primarily to anthropogenic causes such as habitat destruction, pesticide usage and persecution.
Taxonomy and etymology 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.Global Raptor Information Network. 2021. Species account: Bateleur Terathopius ecaudatus. Downloaded from http://www.globalraptors.org on 7 Oct. 2021. 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.Sibley, C. G., & Monroe, B. L. (1990). Distribution and taxonomy of birds of the world. Yale University Press. 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.Wink, M., & Sauer-Gürth, H. (2000). Advances in the molecular systematics of African raptors. Raptors at risk, 135147. 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).Lerner, H. R., & Mindell, D. P. (2005). Phylogeny of eagles, Old World vultures, and other Accipitridae based on nuclear and mitochondrial DNA. Molecular phylogenetics and evolution, 37(2), 327-346. Chromosome banding studies have also found a relatively recent genetic relationship of the bateleurs with the Old World vultures.Bed'Hom, B. T., Darré, R., & Fillon, V. (1998). Chromosome banding studies in the Bateleur (Terathopius ecaudatus, Aves, Accipitridae). Chromosome research: an international journal on the molecular, supramolecular and evolutionary aspects of chromosome biology, 6(6), 437-440.
Etymology 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).Cassin, J. (1867). Fasti Ornithologiæ. Proceedings of the Academy of Natural Sciences of Philadelphia, 212-221.
Description
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.Clark, B., & Davies, R. (2018). African Raptors. Bloomsbury Publishing. 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.Newman, K (1998). Newman's Birds of Southern Africa. Halfway House: Southern Book Publishers. . 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.
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.Zimmerman, D. A., Pearson, D. J., & Turner, D. A. (2020). Birds of Kenya and northern Tanzania. Bloomsbury Publishing.BirdLife International (2019) Species factsheet: Terathopius ecaudatus. Downloaded fromhttp://www.birdlife.org on 29/07/2019. 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.Brown, L. H., & Cade, T. J. (1972). Age classes and population dynamics of the Bateleur and African Fish Eagle. Ostrich, 43(1), 1-16. 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.