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Lifespan, longevity, and ageing

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Maximum longevity: 15.3 years (captivity) Observations: One specimen lived for 15.3 years in captivity (Brouwer et al. 1994).
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Biology

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The southern bald ibis is a gregarious bird that feeds and roosts in large flocks (2). From the roost they fly with powerful wing beats interspersed with gliding and soaring, to suitable foraging areas. In groups of up to 100, this hunter and scavenger will walk along, pecking and probing at the soil, or turning over cattle dung and leaves, searching for prey such as caterpillars, grasshoppers, beetles, earthworms, snails, frogs, small dead mammals and birds (2) (5). The ibis will walk quickly over burnt grassland picking up dead and living insects (2) (5), and there have also been reports of the southern bald ibis collecting buttons, which is likely to be because they are mistaken for beetles (2), and not an unusual hobby! At dusk the southern bald ibis returns to its roost, which is situated on cliffs or in trees, in groups of up to 50, along with other ibises and herons. The southern bald ibis nests on the ground, generally in colonies of 40 pairs or more. The male occupies the nest site first, which it will then defend with aggressive jabs with its bill (2). After attracting a mate, the male collects sticks and soft vegetation from which the female constructs a nest (2) (5). Clutches of one to three eggs are laid between August and October, and both parents regurgitate food to feed the young. The young fly after about 55 days, but depend on the parent's food for up to two months (2).
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Conservation

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The southern bald ibis is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which means that any trade in this species should be carefully regulated (3). It is also officially protected throughout its range (2), and occurs within a number of protected areas (4). The southern bald ibis is the focus of captive breeding programs underway in Pretoria Zoo and in Cape Town, which have the primary objective of reintroducing the species to Cape Province (5). The southern bald ibis is entirely dependent on the farming community for its survival, as the farmers own the land on which they feed and nest, and therefore the cooperation of land owners is vital in any conservation measures. In Transvaal, South Africa, cash incentives and warnings of prosecution played a part in the successful re-establishment of a colony of southern bald ibises (2). The protection and restoration of grassland habitat will also help ensure the continued existence of this weird and wonderful bird.
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Description

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The scientific name of this strange looking bird means 'bald, old man', and refers to its bare head and wrinkled skin on the face and neck. The plumage is a very dark green, with highlights of iridescent green, bronze and violet, and shimmering copper patches on its shoulders. This contrasts sharply with the whitish bare skin on the head and neck, and the bright red crown, which is distinctly domed. The down-curved bill and legs are also red, and the eyes are an orangey-red. Long, fluffy feathers form a neck-ruff, which has a metallic blue-green hue (2). Juveniles lack the coppery patches on the wings, and have plumage that is more greyish in appearance (2). This is a relatively quiet bird that makes a weak gobbling sound, which led to their old Afrikaans name Wilde-Kalkoen, or wild turkey (2). However, they are noisy when they are at the nest, and when in flight give a high-pitched, turkey-like keeaaw-klaup-klaup (2).
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Habitat

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The southern bald ibis inhabits short grasslands at high altitudes, generally between 1,200 and 1,850 meters. It avoids medium to long grass and other vegetated areas, and so prefers recently burnt, ploughed, mowed or heavily grazed fields and cultivated pastures (2) (5). The southern bald ibis generally nests on cliffs along deep river gorges, or by waterfalls (2).
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Range

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Occurs in north-east South Africa, west Swaziland and Lesotho (4).
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Status

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Classified as Vulnerable (VU) on the IUCN Red List 2006 (1), and listed on Appendix II of CITES (3).
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Threats

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The southern bald ibis has always been hunted by humans; historically, young were taken by the Zulu to be used as medicine, Boer farmers shot this ibis during the South African wars to supplement their meat supplies, and settlers hunted it for both food and its feathers. Despite now being protected across its range, local hunting pressure remains a threat (2). However, the main reason for the species' decline in the early 20th century was the spread of karoo vegetation as a result of severe overgrazing of the grasslands. This, along with the planting of conifers in some areas, made large areas of grassland unsuitable for the ibis, and thus its range is now much smaller than it once was (2). Commercial afforestation and intensive farming continue to pose a threat to the southern bald ibis (4).
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Southern bald ibis

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The southern bald ibis (Geronticus calvus) is a large bird found in open grassland or semi-desert in the mountains of southern Africa. Taxonomically, it is most closely related to its counterpart in the northern regions of Africa, the waldrapp (Geronticus eremita).[3][4] As a species, it has a very restricted homerange, limited to the southern tips of South Africa in highland and mountainous regions.[4]

This large, glossy, blue-black ibis has an unfeathered red face and head, and a long, decurved red bill. It breeds colonially on and amongst rocks and on cliffs, laying two or three eggs which are incubated for 21 days before hatching. It is a large bird that feeds and roosts in substantial groups.[5][6] It feeds on insects, small reptiles, rodents and small birds. They do little vocalizing other than occasional gobbling sounds.[7]

The ibises are gregarious long-legged wading birds with long down-curved bills; they form one subfamily of the Threskiornithidae, the other subfamily being the spoonbills.[8] The two Geronticus species differ from other ibises in that they have unfeathered faces and heads, breed on cliffs rather than in trees, and prefer arid habitats to the wetlands used by their relatives.[9][10] The species is currently listed as vulnerable on the IUCN Red List, however, it is in no immediate danger of extinction.[4][7][11]

Taxonomy

The southern bald ibis was described by the French polymath Georges-Louis Leclerc, Comte de Buffon in 1781 in his Histoire Naturelle des Oiseaux based a specimen obtained from the Cape of Good Hope region of South Africa.[12] The bird was also illustrated in a hand-coloured plate engraved by François-Nicolas Martinet in the Planches Enluminées D'Histoire Naturelle which was produced under the supervision of Edme-Louis Daubenton to accompany Buffon's text.[13] Neither the plate caption nor Buffon's description included a scientific name but in 1783 the Dutch naturalist Pieter Boddaert coined the binomial name Tantalus calvus in his catalogue of the Planches Enluminées.[14] The southern bald ibis is now placed in the genus Geronticus that was erected by the German naturalist Johann Georg Wagler in 1832.[15][16] No subspecies are recognised.[16]

The southern bald ibis is part of the family, Threskiornithidae, which is composed of birds from the warm temperate and tropical regions of the world, with the exclusion of Oceania. The group is defined by the lack of feathers on their face. This family is composed of the ibises and their close relatives, the spoonbills.[17]

Taxonomically, ibises are categorized as a subfamily named Threskiornithinae. This subfamily contains around 26 species of wading birds with long, thin, down-curved beaks, ranging in size from medium to large.[4][17] These species rarely have a voice box, and if one is present, the bird only croaks or cackles harshly.[17] Historically, ibises are an ancient group. Fossil records of these birds have been dated back to the Eocene period, 60 million years ago. Human history records also date these birds back 5 000 years.[17]

The southern bald ibis is part of the genus Geronticus, which includes two distinct species. The southern bald ibis (Geronticus calvus) is restricted primarily to the southern regions of Africa whereas its counterpart, the waldrapp (Geronticus eremita) is found in the northern regions of the continent.[3][4] Both species share common characteristics regardless of their geographic separation. Both species nest on rock cliffs and display distinct breeding behaviours adapted for their particular locations. Similarly, they both show evolutionary adaptations in foraging behaviours due to their dry habitats. The separation between these two species is believed to have occurred relatively recently. This separation, between G. calvus and G. eremita, is believed to have occurred only 335 000 to 1 million years ago.[3]

Description

The southern bald ibis (Geronticus calvus) is an uncommon bird endemic to the highlands of the southern African region.[4][5][18] In South Africa, the species’ total breeding population is estimated around 4 600 birds.[5] However, little is known about the biology of this species.[4]

Its plumage is dark green with iridescent streaks of green, violet and bronze. The neck displays long feathers that are a blue-green shade. As adults, its shoulders display shades of copper. However, as juveniles, the plumage is predominantly a dull grey color. The bird's Latin name, Geronticus calvus, is translated as “bald, old man”, referring to the bird's featherless, wrinkled head and face. The head is the key feature in recognizing this species due to the evident bare whitish skin. On the top of the head, there is a red dome-shaped crown. The bills of these birds are down-curved and red, along with their legs. Similarly, their eyes are also colored an orange-red shade.[7]

Distribution and habitat

The southern bald ibis is a species with a very restricted homerange. It is estimated that there are only 4 600 breeding birds of this species in the South African region.[5] The species is confined to the eastern regions of South Africa and are restricted to the highland and mountainous regions.[4] Its range extends from the highlands of Lesotho extending into Eswatini. The birds may migrate short distances within their designated home ranges.[5]

These birds are cliff-nesters and breed in the open areas of mountain faces, as well as river gorges and sometimes around waterfalls. Their breeding habitat is composed mainly of mountainous grasslands that range in altitude from 1 200 to 2 000 meters above sea level. The grassland areas are labeled as ‘sour’ due to the low nutritional value of the foliage in late summer and early autumn due to the previous grazing of mammals.[5]

Behaviour

The southern bald ibis is a bird that feeds and roosts in large groups. They travel in groups of up to 100 individuals to find suitable foraging areas.[7] As insectivores, their diet is composed mainly of insects and other small invertebrates found in burnt grasslands.[5][6] The species live on cliff edges where they build their nests and for the most part, breed in colonies.[5] They do little vocalizing besides occasional gobbling sounds.[7]

Vocalizations

The southern bald ibis is known to be a relatively quiet bird. This species in particular has been noted to make a weak gobbling sound. This is refers back to their old Afrikaans name of “Wilde-Kalkoen”, otherwise translated as “wild turkey”. This bird is most boisterous in the nesting areas and in flight. It projects a high-pitched keeaaw-klaup-klaup call, resembling that of a turkey's.[7]

Diet

This species is insectivorous and feeds predominantly on insects and other small terrestrial invertebrates.[5][6] It is a forager, alternating between feeding in harvested maize fields, overgrazed pastures and burnt grasslands. They walk along the land while pecking and probing the ground.[11] The main component of its diet is the caterpillar of the maize stalk borer, Busseola fusca. This bird will also turn over feces and leaves to search for prey including caterpillars, grasshoppers, beetles, earthworms, snails and sometimes frogs, small dead mammals and birds.[7]

Throughout July and the first half of August, before laying their eggs, the birds are found foraging in maize fields. In the second half of August and early September, during the incubation period, the birds are seen alternating between the maize fields, grazed pastures and burnt grasslands. Finally, in the nestling phase of September and October, they forge in maize fields, but more frequently in ploughed fields. It is only on rare occasions that ibises are seen in tall grasses and almost never in marshy areas. These birds avoid the tall grasses due to the hindering of their mobility and the potential hiding of their prey. This area would require a slow-walk feeding technique, whereas this bird is known to use a fast-walk technique for their feeding. They also appear to avoid foraging in areas very close to their nesting sites.[11]

Their predominant feeding area, the burnt grasslands, are termed “sour” due to the low availability of nutrients. These areas are burned every 1 to 3 years to clear any excess of foliage. In winter and spring, the ibises feed in the burned areas where new growth is emerging and scavenge for any available insects. Their breeding season is linked with the burning period of these crops. Therefore, successful breeding and survival is partially dependent on the availability of these burned grasslands.[5]

Reproduction

The southern bald ibis nests in cliffs and breeds on open ledges.[5] Due to the mostly inaccessible nature of these areas, observations during breeding season are difficult to obtain.[18] However, these birds are known to breed predominantly in colonies, while some pairs decide to nest away from the rest. The females lay their eggs anywhere from late July to mid-October. Following this, the young develop feathers for flight around mid-October and into the month of December.[5]

Their nests are made mostly of sticks and grass. On average, the collection of these materials begins around two weeks before the first egg is laid. Once the first egg is laid, incubation lasts from 26 to 32 days. The incubating birds change their position and rotate the egg more frequently around three days before the hatch day. Once hatched, the chicks spend the first 7 to 10 days feeding from their parent via regurgitation. After 35 days, the young leave the nest to wander around and after 40 to 50 days, the chicks are able to fly, but still spend most of their time on the ledges of the cliff or in their nest.[18]

Conservation status

The southern bald ibis is currently listed as vulnerable on the IUCN Red List of Threatened Species.[7][11] However, there is no immediate threat of the species going extinct.[4] The bird is also listed in the Convention on International Trade in Endangered Species (CITES), signifying that the trade of this species is substantially regulated.[7]

One of the greatest causes in the decline of this species is human disturbance at their breeding sites and the degradation of their habitat. Most of the breeding sites occur on privately owned land, whereas only a small minority of breeding pairs are located on nature reserves or state forest land, which are the only areas where they are guaranteed protection. Therefore, a large portion of the population is dependent on the efforts and contributions of private landowners. Furthermore, another threat is that the adult birds may be captured in order to collect the eggs and nestlings for food or medicine in some African tribal practices.[5][7] The hunting of these birds has also been popular in farming populations to supplement their meat supplies. Local hunting continues to be a threat today.[7]

Gallery

References

  1. ^ BirdLife International (2016). "Geronticus calvus". IUCN Red List of Threatened Species. 2016: e.T22697496A93617026. doi:10.2305/IUCN.UK.2016-3.RLTS.T22697496A93617026.en. Retrieved 19 November 2021.
  2. ^ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
  3. ^ a b c Pegoraro (2001). "Mitochondrial DNA sequence evidence for close relationship of Bald Ibis, Geronticus calvus, and Waldrapp Ibis, G. eremita". Ostrich. 72 (3–4): 215–216. doi:10.2989/00306520109485324.
  4. ^ a b c d e f g h i Siegfried (1971). "The status of the Bald Ibis of Southern Africa". Biological Conservation. 3 (2): 88–91. doi:10.1016/0006-3207(71)90004-8.
  5. ^ a b c d e f g h i j k l m Manry, D. (1985a). "Distribution, Abundance and Conservation of the Bald Ibis Geronticus calvus in Southern Africa". Biological Conservation. 33 (4): 351–362. doi:10.1016/0006-3207(85)90076-x.
  6. ^ a b c Manry, D. (1985b). "Reproductive performance of the Bald Ibis Geronticus calvus in relation to rainfall and grass-burning". Ibis. 127 (2): 159–173. doi:10.1111/j.1474-919x.1985.tb05052.x.
  7. ^ a b c d e f g h i j k "Geronticus calvus". Wildscreen Arkive. Archived from the original on 2015-09-05. Retrieved 2015-10-14.
  8. ^ del Hoyo, J.; Elliot, A.; Sargatal, J., eds. (1992). Handbook of the Birds of the World. Volume 1: Ostrich to Ducks. Barcelona: Lynx Edicions. ISBN 84-87334-09-1.
  9. ^ Snow, David; Perrins, Christopher M., eds. (1998). The Birds of the Western Palearctic concise edition (2 volumes). Oxford: Oxford University Press. ISBN 0-19-854099-X.
  10. ^ Sinclair, Ian; Hockey, Phil; Tarboton, Warwick (2002). SASOL Birds of Southern Africa. Cape Town: Struik. ISBN 1-86872-721-1.
  11. ^ a b c d Kopij, G. (2001). "Feeding ecology of the Southern Bald Ibis, Geronticus calvus, in the Free State, South Africa". Ostrich. 72 (3–4): 193–198. doi:10.2989/00306520109485316.
  12. ^ Buffon, Georges-Louis Leclerc de (1781). "Le courlis à tête nue". Histoire Naturelle des Oiseaux (in French). Vol. 15. Paris: De L'Imprimerie Royale. pp. 49–50.
  13. ^ Buffon, Georges-Louis Leclerc de; Martinet, François-Nicolas; Daubenton, Edme-Louis; Daubenton, Louis-Jean-Marie (1765–1783). "Courly à tête nue, du Cap de bonne-Esperance". Planches Enluminées D'Histoire Naturelle. Vol. 9. Paris: De L'Imprimerie Royale. Plate 867.
  14. ^ Boddaert, Pieter (1783). Table des planches enluminéez d'histoire naturelle de M. D'Aubenton : avec les denominations de M.M. de Buffon, Brisson, Edwards, Linnaeus et Latham, precedé d'une notice des principaux ouvrages zoologiques enluminés (in French). Utrecht. p. 52, Number 867.
  15. ^ Wagler, Johann Georg (1832). "Neue Sippen und Gattungen der Säugthiere und Vögel". Isis von Oken (in German and Latin). cols 1218–1235 [1232].
  16. ^ a b Gill, Frank; Donsker, David, eds. (2019). "Ibis, spoonbills, herons, hamerkop, shoebill, pelicans". World Bird List Version 9.2. International Ornithologists' Union. Retrieved 16 July 2019.
  17. ^ a b c d Austin, O; Singer, A; Zim, H (1961). Birds of the world: a survey of the twenty-seven orders and one hundred and fifty-five families. New York: Golden Press.
  18. ^ a b c Kopij, G; Kok, O; Nuttall, R (2000). "Breeding cycle of the Southern Bald Ibis, Geronticus calvus". Ostrich. 71 (3–4): 393–399. doi:10.1080/00306525.2000.9639838.
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Southern bald ibis: Brief Summary

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The southern bald ibis (Geronticus calvus) is a large bird found in open grassland or semi-desert in the mountains of southern Africa. Taxonomically, it is most closely related to its counterpart in the northern regions of Africa, the waldrapp (Geronticus eremita). As a species, it has a very restricted homerange, limited to the southern tips of South Africa in highland and mountainous regions.

This large, glossy, blue-black ibis has an unfeathered red face and head, and a long, decurved red bill. It breeds colonially on and amongst rocks and on cliffs, laying two or three eggs which are incubated for 21 days before hatching. It is a large bird that feeds and roosts in substantial groups. It feeds on insects, small reptiles, rodents and small birds. They do little vocalizing other than occasional gobbling sounds.

The ibises are gregarious long-legged wading birds with long down-curved bills; they form one subfamily of the Threskiornithidae, the other subfamily being the spoonbills. The two Geronticus species differ from other ibises in that they have unfeathered faces and heads, breed on cliffs rather than in trees, and prefer arid habitats to the wetlands used by their relatives. The species is currently listed as vulnerable on the IUCN Red List, however, it is in no immediate danger of extinction.

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