The kori bustard (Ardeotis kori) is the largest flying bird native to Africa. It is a member of the bustard family, which all belong to the order Otidiformes and are restricted in distribution to the Old World. It is one of the four species (ranging from Africa to India to Australia) in the large-bodied genus Ardeotis. The male kori bustard may be the heaviest living animal capable of flight.
This species, like most bustards, is a ground-dwelling bird and an opportunistic omnivore. Male kori bustards, which can be more than twice as heavy as the female, attempt to breed with as many females as possible and take no part in the raising of the young. The nest is a shallow hollow in the earth, often disguised by nearby obstructive objects such as trees.
Taxonomy English naturalist William John Burchell described the kori bustard in 1822. The specific epithet kori is derived from the Tswana name for this bird – .
Two subspecies are currently recognized: Ardeotis kori kori – the relatively pale nominate race from Botswana, Zimbabwe, Namibia, southern Angola, South Africa and Mozambique. Ardeotis kori struthiunculus – the "Somali kori" distributed in Ethiopia, Uganda, South Sudan, Kenya and Tanzania. The two races are separated by the miombo woodlands of central Africa. This race has a more boldly patterned head and slightly more black and white patterning on the wings. The two races are similar in size, though A. k. struthiunculus may be slightly larger. This may be a distinct species.
In older literature the species is named 'Large Crested Pauw' (Eupodotis kori).
Description
The kori bustard is cryptically coloured, being mostly grey and brown, finely patterned with black and white coloring. The upper parts and neck are a vermiculated black and greyish-buff colour.Williams, J.G. 1995. Collins Field Guide: Birds of East Africa. HarperCollins, Hong Kong. The ventral plumage is more boldly colored, with white, black and buff. The crest on its head is blackish in coloration, with less black on the female's crest. There is a white eye stripe above the eye. The chin, throat and neck are whitish with thin, fine black barring. A black collar at the base of the hind-neck extends onto the sides of the breast.Alden, P.C., Estes, R.D., Schlitter, D. and McBride, B. (1996) Collins Guide to African Wildlife. HarperCollins Publishers, London. The feathers around the neck are loose, giving the appearance of a thicker neck than they really have.Newman, K. (ed) 1971. Birdlife in southern Africa. Macmillan, Johannesburg, South Africa. The belly is white and the tail has broad bands of brownish-gray and white coloration. Their feathers contain light sensitive porphyrins, which gives their feathers a pinkish tinge at the base- especially noticeable when the feathers are shed suddenly. The head is large and the legs are relatively long. The eye is pale yellow, while the bill is light greenish horn coloured, relatively long, straight and rather flattened at the base. The legs are yellowish. The feet have three forward facing toes. Females are similar in plumage but are much smaller, measuring about 20–30% less in linear measurements and often weighing one third to half of the males. The female is visibly thinner legged and slimmer necked.Newman, K. 1992. Newman's Birds of Southern Africa : Expanded Edition, Fourth Edition. Southern Book Publishers (Pty) Ltd., Halfway House. The juvenile is similar in appearance to the female, but is browner with more spotting on the mantle, with shorter crest and neck plumes. Male juveniles are larger than females and can be the same overall size as the adult male but tends to be less bulky with a thinner neck, shorter head crest, paler eyes and a darker mantle.
Size
The male kori bustard has a length of Hancock, P., & Weiersbye, I. (2015). Birds of Botswana (Vol. 103). Princeton University Press. and a wingspan of . Male birds may typically weigh between . The average weight of adult males of the nominate race in Namibia (20 specimens) was , while A. k. struthiunculus males were found to average .CRC Handbook of Avian Body Masses by John B. Dunning Jr. (Editor). CRC Press (1992), .CRC Handbook of Avian Body Masses, 2nd Edition by John B. Dunning Jr. (Editor). CRC Press (2008), . Males in Serengeti National Park had appreciably higher weights, however, averaging . The larger excepted males can scale up to and a few exceptional specimens may weigh up to at least . Reports of outsized specimens weighing , and even "almost" have been reported, but none of these giant sizes have been verified and some may be from unreliable sources. Among bustards, only male great bustards (Otis tarda) achieve similarly high weights (the mean mass of males in these species is roughly the same) making the male kori and great not only the two largest bustards but also arguably the heaviest living flying animals, with the kori bustard being Africa's second largest bird after the ostrich. The larger males of certain other species, such as the Dalmatian pelican (Pelecanus crispus), Andean condor (Vultur gryphus) and trumpeter swan (Cygnus buccinator), might match the average weight of the largest bustards, and these species may weigh more on average than the giant bustards as they are less sexually dimorphic in mass. Other than a mute swan (Cygnus olor), the maximum size of the large bustards exceeds that of other flying birds. Other flying African birds (excluding rare vagrant pelicans and vultures to northernmost Africa) rival the average weight between the sexes of Kori bustards, namely great white pelicans (Pelecanus onocrotalus) and Cape vultures (Gyps coprotheres) while wattled cranes (Bugeranus carunculatus) lag slightly behind these on average. The female kori bustard weighs an average of , with a full range of . Females of the nominate race (35 specimens) in Namibia weighed a mean of , while females from A. k. struthiunculus weighed a mean of . Females in the Serengeti averaged slightly lighter at . Female length is from while their wingspan is around .Collar, N. and E. F. J. Garcia (2020). Kori Bustard (Ardeotis kori), 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. The standard measurements of the male include a wing chord of , a tail measures from , a culmen from and a tarsus from . Meanwhile, the female's standard measurements are a wing chord of , a tail of , a culmen from and a tarsus from .Johnsgard, Paul A. 1990. Bustards: Stalkers of the Dry Plains. Zoonooz 63(7): 4-11. Body mass can vary considerably based upon rain conditions.Liversidge, R. 1991. The Birds Around Us - Birds of the Southern African Region. Fontein Publishing Company (Pty) Ltd., Parklands.
Similar species
The size and dark crest are generally diagnostic amongst the bustards found in the kori bustard's range.Sinclair I., Hockey P. & Tarboton W. 1997. Sasol Birds of Southern Africa. Struik Publishers (Pty) Ltd., Cape Town. However, East Africa holds the greatest diversity of bustards anywhere, including some other quite large species, and these have the potential to cause confusion. Kori bustards are distinguished from Denham's bustard (Neotis denhamii) and Ludwig's bustard (Neotis ludwigii), both of which they sometimes forage with, by their greyer appearance and by their lack of a tawny red hind-neck and upper mantle. In flight it can be distinguished from both of these somewhat smaller bustards by not displaying any white markings on the upperwing, which is uniformly grey here. Both Stanley's and Ludwig's bustards lack the kori's dark crest. More similar to, and nearly the same size as, the kori is the closely related Arabian bustard (Ardeotis arabs) (despite its name, the latter species ranges well into East Africa). However, the Arabian species has white-tipped wing coverts, a browner back and very fine neck vermiculations and also lacks the black base to the neck and the black in the wing coverts as seen in the kori.
Distribution and habitat
The kori bustard is found throughout southern Africa, except in densely wooded areas. They are common in Botswana and Namibia, extending into southern Angola and marginally into southwestern Zambia. In Zimbabwe they are generally sparse but locally common, particularly on the central plateau. Their distribution range extends along the Limpopo River valley into southern Mozambique and the eastern lowveld of South Africa. In South Africa they are also infrequent to rare in the Free State, North West and Northern Cape Provinces, extending southwards into the interior of the Western and Eastern Cape Provinces. Kori bustards are absent from the coastal lowlands along the south and east of South Africa and from high mountainous areas. This species is common in Tanzania at Ngorongoro National Park, Kitulo National Park and Serengeti National Park. A geographically disjunct population also occurs in the deserts and savanna of northeastern Africa. Here, the species ranges from extreme southeast South Sudan, north Somalia, Ethiopia through all of Kenya (except coastal regions), Tanzania and Uganda.Sinclair I. & Ryan P. 2003. A comprehensive illustrated field guide : Birds of Africa south of the Sahara. Struik Publishers, Cape Town. Kenya may hold the largest population of kori bustards of any country and it can even border on abundant in the North Eastern Province. They are usually residential in their range, with some random, nomadic movement following rainfall.Ginn P.J., McIlleron W.G. & Milstein P. le S. 1989. The Complete Book of southern African birds. Struik Winchester, Cape Town.
This species occurs in open grassy areas, often characterized by sandy soil, especially Kalahari sands, and short grass usually near the cover of isolated clumps of trees or bushes. It may be found in plains, arid plateaus, highveld grassland, arid scrub, lightly wooded savanna, open dry bushveld and semi-desert.Maclean, G.L. 1993. Robert's Birds of Southern Africa. Sixth Edition. John Voelcker Bird Book Fund, Cape Town. Where this species occurs, annual rainfall is quite low, between . Breeding habitat is savanna in areas with sparse grass cover and scattered trees and shrubs. When nesting they sometimes use hilly areas.Tarboton W. 2001. A Guide to the Nests and Eggs of Southern African Birds. Struik Publishers (Pty) Ltd., Cape Town. They follow fires or herds of foraging ungulates, in order to pick their various foods out of the short grasses. They may also be found in cultivated areas, especially wheat fields with a few scattered trees. This bustard is not found in well-wooded and forested areas due to the fact that it needs a lot of open space in which to take off. In arid grassland areas it is found along dry watercourses where patches of trees offer shade during the heat of the day.
Behaviour