Southern ground hornbill

Description

This is a large bird, at 90 to 129 cm (2 ft 11 in to 4 ft 3 in) long. Females weigh 2.2 to 4.6 kilograms (4.9 to 10.1 lb), while the larger males weigh 3.5 to 6.2 kilograms (7.7 to 13.7 lb). The average weight of eight females was 3.34 kg (7.4 lb) whilst that of eight males was 4.2 kg (9.3 lb), thus they average around 35% percent heavier than any Asian hornbill species. Wingspan is apparently from 1.2 to 1.8 m (3 ft 11 in to 5 ft 11 in). Among standard measurements, the wing chord has been measured from 49.5 to 61.8 cm (19.5 to 24.3 in), the tail from 29 to 36 cm (11 to 14 in), the tarsus from 13 to 15.5 cm (5.1 to 6.1 in) and the culmen from 16.8 to 22.1 cm (6.6 to 8.7 in). Per Stevenson and Fanshawe, the Abyssinian ground hornbill is the larger species on average, at 110 cm (43 in), than the southern species, at 102 cm (40 in), but published maximum weights and standard measurements contrarily indicate the southern species is indeed slightly larger. Apparently average weights are not known for the Abyssinian species.

The southern ground hornbill is characterized by black coloration and vivid red patches of bare skin on the face and throat (yellow in juvenile birds), which are generally believed to keep dust out of the birds eyes while they forage during the dry season. The white tips of the wings (primary feathers) seen in flight are another diagnostic characteristic. The beak is black and straight and presents a casque, more developed in males. Female southern ground hornbills are smaller and have violet-blue skin on their throats. Juveniles to six years old lack the prominent red pouch, but have a duller patch of grey in its place.

Habitat and diet

Southern ground hornbills can be found from northern Namibia and Angola to northern South Africa and southern Zimbabwe to Burundi and Kenya. They require a savanna habitat with large trees for nesting and dense but short grass for foraging.

The southern ground hornbill is a vulnerable species, mainly confined to national reserves and national parks. They live in groups of 5 to 10 individuals including adults and juveniles. Often, neighbouring groups are engaged in aerial pursuits. They forage on the ground, where they feed on reptiles, frogs, snails, insects and mammals up to the size of hares. Southern ground hornbills very rarely drink. Their range is limited at its western end by the lack of trees in which to build nests.

Southern ground hornbill groups are very vocal: contact is made by calls in chorus which can usually be heard at distances of up to 3 kilometres (1.86 mi). The calls allow each group to maintain its territories, which must be as large as 100 square kilometres (40 sq mi) even in the best habitat.

Breeding and life cycle

The southern ground hornbill is an obligate cooperative breeder, with each breeding pair always assisted by at least two other birds. It is known via experiments in captivity that birds without six years experience as helpers at the nest are unable to breed successfully if they do become breeders. This suggests that unaided pairs cannot rear young and that helping skill as a juvenile is essential for rearing young as an adult.

In captivity, a maximum lifespan of 70 years is recorded, and it is generally believed that the life expectancy of a bird that survives long enough to fledge is as high as thirty years or more, which is comparable to more famously long-lived birds like the wandering albatross.

Ground hornbills are believed to reach maturity at six to seven years, but very few breed at this age. Nests are almost always deep hollows in very old trees, though there exist reports ground hornbills have on occasions nested on rock faces. One to three eggs are laid at the beginning of the wet season but siblicide ensures that only one nestling is ever fledged. The eggs measure 73 millimetres (2.87 in) by 56 millimetres (2.20 in) and are pure white in colour but very rough in texture.

The period of parental dependence following a 40 to 45-day incubation period and an 85-day fledging period is between one and two years depending on climatic conditions before young are independent of parents and helpers, which is the longest of any bird. This means that ground hornbills can normally breed successfully only every third year. Triennial breeding is extremely rare in birds: probably the only other bird which breeds on a triennial basis is the ornate hawk-eagle of Neotropical rainforests.

Conservation

The southern ground hornbill is classed as vulnerable to extinction globally; however, in South Africa, where most studies on the species have been carried out, it is listed as endangered. They have also been classified as endangered in Lesotho, Namibia and Swaziland. Southern ground hornbills in these countries, along with Kenya, Tanzania, Malawi, Zambia, Zimbabwe, and Mozambique, require conservation interventions to help increase their numbers. The bird's classification as endangered is heavily tied to its slow reproductive rates and other, numerous environmental factors. Habitat loss, changes due to the agriculture, deforestation, electrocution from power lines, accidental poisoning, and persecution are the major factors that affect their populations.

Persecution and hunting of the southern ground hornbill by human populations has continued to be a complex issue. Recent studies have found the species has been hunted more than previously believed, including in protected areas. The majority of this hunting has likely been opportunistic. Overall, hunting is likely not a key driver for their lowering numbers. Although it is still a factor to be aware when considering conservation efforts, especially due to their low reproductive rates and an incomplete knowledge about local hunting habits in their natural regions. Furthermore, the southern ground hornbill faces persecution due to behaviors like destroying windows in response to seeing their reflection. Annoyed homeowners in urban areas in South Africa have been known to kill birds that destroy property.

The role of southern ground hornbills in a variety of cultural beliefs also influence conservation efforts. Some of these beliefs actually benefit their preservation. An example is the Ndebele, who believe killing southern ground hornbills is taboo due to their negative associations. However, the birds are also used in traditional cultural practices and medicines which can be harmful. In some marketplaces and cultures, southern ground hornbills are used in traditional medicines, which often rely upon harvesting specific parts of the bird. To date, research suggests that cultural uses do not have a significant impact on their populations. For example, the Ndebele healers use the bird for traditional medicine, but must follow a strict ritual process that could take months or years to prepare. Additional research documents plant alternatives to southern ground hornbill use for cultural belief uses. While investigation into traditional medicine trade of the southern ground hornbill has occurred, the bushmeat trade remains poorly understood, and it has only been seen to occur in areas of Malawi.

This bird species is especially threatened by the loss of trees and general habitat loss, as they require vast amounts of space for their territories. The removal of large trees for agriculture or wood harvesting, disturbances near nesting grounds, agricultural changes, all deeply affect the ability of southern ground hornbills to flourish properly. Due to the encroachment of human populations, it is not unheard of to see a group's territory encompass a variety of areas, from pristine habitats to commercial agricultural lands.

Southern ground hornbills can have clutches ranging from one to three eggs, but only one of these are raised. With only one egg being raised, conservationists have taken it as an opportunity to raise the remaining eggs in captivity. Rehabilitation projects, such the Mabula Ground Hornbill Project, have been hand-rearing these left behind chicks with goals to reintroduce them to the wild. Although reintroduced southern ground hornbills have proven challenging.