Southern Ground Hornbill(Bucorvus leadbeateri)
This is a large bird, at 90-129 cm long. Females weigh 2.2-4.6 kgs, while the males weigh 3.5-6.2 kgs. Wingspan is from 1.2-1.8 m. Among standard measurements, the wing chord has been measured from 49.5-61.8 cm, the tail from 29-36 cm, the tarsus from 13-15.5 cm and the culmen from 16.8 to 22.1 cm. 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
They 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. They are mainly confined to national reserves and national parks.
Diet
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.
Breeding
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. 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 mm by 56 mm and are pure white in colour but very rough in texture. The period of parental dependence following a 40-45-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.
Population
According to the IUCN Red List, they are classed as Vulnerable(VU). The global population size has not been quantified, but the species is reported to be widespread and common but sparse. However, there are fears that Allee effects may occur as a result of fragmentation and unnatural mortalities creating a lag in declines being noticed. Range wide genetic analysis and population trends analyses are ongoing.
An assessment of the species's status in South Africa estimated a 20% loss in the area of suitable habitat within the species's national range in the past 15 years. Although declines are also suspected in other range countries, there are not thought to be significant declines in Zambia, which may be a stronghold of the species. As such, and given that data is currently lacking and that it is difficult to accurately project future declines for such a long-lived species, a decline of 30-49% is projected over 94 years.
Threats
A major threat to the species is loss of nesting habitat due to clearance for small-scale use, agriculture, and because of fires and violent storms. It can become heat stressed and exhibits heat avoidance behaviour in temperatures above 26 degrees, and increasing temperatures with climate change could pose a threat. Widespread livestock grazing has also lead to the erosion of suitable grassland in Kenya, with perhaps only 10% of suitable habitat remaining in the country. Although cultural beliefs offered some protection in the past in Kenya, recent generations tend not to hold such values, and the species may be directly persecuted as a result. Persecution may occur directly because the species breaks window panes by attacking its own reflection in glass (incurring costs and creating human-wildlife conflict), indirectly by consuming poisoned bait meant for other species, and it is sometimes killed for traditional rituals against drought. In South Africa and Zimbabwe, where these beliefs are upheld, there is actually a significant protection given to this species because it has high cultural importance, and these beliefs outweigh any offtake for traditional use. Collisions with powerlines may also be a threat in South Africa, although only one such mortality has been recorded and more mortalities may occur from electrocution by standing on step-down transformer boxes - especially if an insect nest has been built on or near the box which could act as an attractant for the species. Such threats are exacerbated by the slow reproductive rate and maturation, longevity and social structure of the species. This species can be susceptible to Newcastle's Disease Virus, and may be under threat from stepping on land mines in areas of conflict.
Conservation
Conservation Actions Underway
It is still protected by tribal lore in many areas, and occurs in several reserves and at least seven national parks. There is extensive conservation work being carried out in South Africa, including a re-introduction programme, research into several different areas (population dynamics, tracking, and the feasibility of supplementary feeding, multiple clutching, group supplementation, threat mitigation and artificial nest-site provision), public awareness campaigns, and a Single-Species Recovery Plan, with revision planned for 2017. Areas suitable for reintroduction have been identified; and protocols for reintroduction and hand-rearing have been developed and from 2000-2008 the Mabula Project attempted 13 soft and hard releases and re- introductions of individuals, and a re-introduced female fledged a chick in 2008 in the Mabula Game Reserve. However, the challenge remains removing the threats from the habitat with the largest challenge being the extensive abuse of pesticide for carnivore control. In the Matobo District of Zimbabwe research is being conducted into emerging threats from small scale farming.
Conservation Actions Proposed
Collect sighting data at a national scale to build up a database for comparison to existing atlas data and for range states engaged in the Southern African Bird Atlas Project to ensure maximum coverage. Continue awareness campaigns to prevent persecution, and accidental mortalities due to abusive and non-targeted use of pesticides and poisons. Promote and revive existing cultural protection. Identify key strongholds of the species and prevent further habitat degradation in these areas. Continue to research the effectiveness of artificial nest-sites. Identify threats and work at mitigation e.g. covering windows to prevent reflection, insulation of transformer boxes.