REINTRODUCTIONS OF SOUTHERN GROUND HORNBILLS

 





















  Reintroduction of birds, especially species as large and mobile as SGHs with their extensive spatial requirements, is much more difficult than for the well-documented considerations and techniques for mammals, particularly larger game species, because birds cannot be fenced into a fixed area once they are released. This means that should the new recruits not like the habitat chosen for them they will fly elsewhere, and this mobility also makes it difficult to monitor, control and recapture them once released.

The Southern Ground-Hornbill (SGH) in South Africa now exists in three phases of conservation:
1) About half of the population (200-250 breeding pairs/groups) live in the relatively pristine natural habitats that remain in the eastern Lowveld below the Drakensberg escarpment. The Kruger National Park (KNP; 20,000 km2) forms the greatest part of this natural habitat, together with many smaller and mainly privately-owned reserves along its western border. SGHs are well but passively conserved within this so-called Greater KNP (GKNP), apart from in the Associated Private Nature Reserves (APNR - Klaserie, Timbuvati, Umbabat) where there is an on-going research project run by the Percy FitzPatrick Institute of African Ornithology (PFIAO or Fitztitute) that is based around thesupply of artificial nest sites (hollow logs placed in trees and readily used by SGH groups). There is also on-going monitoring of some groups and nest sites within the KNP, currently by the Bird of Prey Working Group (BoPWG) of the Endangered Wildlife Trust (EWT) that includes their Ground Hornbill Working Group (GHWG).


2) The other half of the current population is scattered across private and state properties, the minority of them with any formal conservation status, in the Provinces of Limpopo, Mpumalanga, KwaZulu-Natal and the Eastern Cape. There has been an old study in KwaZulu-Natal (Knight 19??) and a recent study of a relatively large population in the Limpopo Valley east of Musina (Theron 2011), aspects of which are being continued, but otherwise there is only sporadic collection of information from across the largely un-conserved rural range of the SGH.


3) There is also natural habitat that was occupied historically by SGHs, maybe half as much again as their existing range, but from which they have been extirpated, apparently mainly in the 1940s-50s and mostly in Limpopo, Mpumalanga and KwaZulu-Natal Provinces. In addition, as the national conservation status of the SGH declines from Vulnerable (2000) to Endangered (2011), gaps in the existing range are appearing, most obviously in the Mpumalanga-Swaziland-KwaZulu-Natal lowveld, but also around the KwaZulu-Natal-Eastern Cape border and at the southern extremity of its range along the Eastern Cape coast. Much of the current reintroduction efforts for the species, headed by the Mabula Project, focus on attempts to re-populate at least some of this historical range.

 

The cheapest and most effective conservation would be to protect the remaining wild SGH groups and secure additional habitat for their expansion, including within their historical range, but this seems impossible considering the variety of landowners among which they reside outside of the KNP and the expansive, low-density scale at which they exist. The low numbers of the total South African population is also too low to consider translocation of wild groups to re-colonise of any vacated areas.


However, the national SGH population continues to decline and is heading steadily towards being classified as Critically Endangered, with even the 200-300 breeding pairs estimated for the GKNP and other formally conserved areas too few to be considered as a viable population in the long-term. At the same time, the SGH has also been downgraded from Near Threatened to Vulnerable across the rest of its African range, including in South Africa's neighbouring states of Botswana, Zimbabwe, Mozambique and Swaziland from where additional recruits might be expected. As it is, the risks for SGH survival may be under-estimated since the long lifespan of individual SGHs probably gives an optimistic impression of their current security, while its slow breeding rate and lifelong territorial occupancy, within groups that include both the breeding and non-breeding segments of the population, predict that any surplus for re-colonisation will always be small.


The saving grace for the SGH is that, to the best of our knowledge, it never rears more than a single chick per breeding attempt, even though is usually lays two (80%) and rarely three (>1%) eggs per clutch. Any second- or third-hatched chicks die of starvation in the nest, usually within the first week or two after hatching. Provided the nest contents can be checked and the chicks harvested without affecting the dynamics of the wild or parent population, these redundant chicks can provide limitless impact-free stock for reintroduction for as long as the wild population survives.

 

The main challenges of reintroduction are therefore:

a) to locate and harvest the redundant chicks with minimal impact on the wild population,

b) to hand-rear these chicks to fledging in suitable condition for release back into the wild, and

c) to select and operate release sites that supply year-round sustainable habitats free of suspected threats where SGHs will, survive, breed and expand to form neighbouring groups.

Much easier said than done! Some possible variations on this theme are to take some of the harvested chicks into captivity, as insurance against loss of the wild population and as an additional source of chicks for rehabilitation, and also to try and improve the production and survival of wild groups by, for example, provision of artificial nest cavities, fostering redundant chicks back into wild groups, or supplementary feeding wild females so that they lay more and healthier eggs.

 

Natural threats to the SGH, at least in the KNP, account for an estimated 51% failure in breeding attempts, a 69% mortality of immatures before reaching breeding age, but only a 1.5% annual risk of mortality once mature. However, the disappearance of SGHs from large tracts of their historical range and their continued decline, outside of all but the most extensive conservation areas, was obviously caused by a variety of additional manmade threats that accelerated the natural rates of mortality.

 

Manmade threats identified so far include:
reduction in availability of large nest-cavity-forming trees (by elephants in conservation areas and for firewood, carving or building poles in inhabited rural areas),
• reduction in the area of suitable bushveld and grassland habitats (through timber plantations, croplands, bush-encroachment, over grazing and/or residential/urban development),
• utility line electrocutions or collisions (especially on local transformers and lines),
• poisoning (deliberately for traditional uses or persecution, secondarily from pest control or agrochemical consumption),
• intolerance/persecution (for breaking their 'opponent's' reflection in house or vehicle mirrors/windows, or for threatening stock on domestic and game farms).
• Disease susceptibility (to indigenous strains of Newcastle's Disease)

 

Therefore, a primary requirement before reintroduction is to identify the most ecologically suitable and safest areas available, to ensure that the landowners, residents and employees on and surrounding the release site are in full support of the project and to mitigate, as far as possible, against the threats listed above.

 

From this background, the current conservation activities for SGHs in South Africa are as follows:
1) For that half of the SGH population living in the GKNP, the only activity has been and remains the annual monitoring of productivity for some of the groups (refs ?), a few of which supply redundant chicks for use in conservation efforts elsewhere in the country. The results of this monitoring supply much of the biological data that is used to understand the SGH and what might be done to conserve it in South Africa.


2) For the other half of the SGH population living in un-conserved rural areas, random records are collected on sightings of individuals or groups of SGHs, but with relatively few nesting sites or attempts also recorded. There have been earlier regional surveys in the Eastern Cape (Vernon 196?) and KwaZulu-Natal Provinces (Knight 198?) and a recent study in the Limpopo Valley of Limpopo Province (Theron 2011, in press). There have been exploratory attempts by the Mabula Project at reintroduction of redundant juveniles, either to augment a single bird left on existing territories with a mate (Haenertsburg 200?) or to try and re-establish groups in vacant patches within their range (Malalotjo 199?, Shamwari 200?, Madikwe 200?), but only with limited success. There has also been a recent attempt to collate all historical and recent records, especially for rural areas, to assess the national status of the SGH (Kemp & Webster 2008), the results of which elevated concern for its risk of national extinction from Vulnerable to Endangered in the revised national Red Data List. The current second atlas for South African bird species by citizen scientists (SABAP 2, Animal Demography Unit, University of Cape Town, www.sabap2.org) already suggests worrying new trends and patterns of decline and these will soon be carefully evaluated and published. Renewed attempts to augment lone birds or declining groups will be attempted as necessary, pending availability of stock for release and reduction of threats at the sites of deline.

 

3) The whole raison d'etre for initiation of the Mabula Project was to test the feasibility of re-establishing a SGH group within bushveld habitat on Mabula Game Reserve from which the species had been extirpated. Eventually, it was successful when a hand-reared redundant female fledged its own chick with the help of its group. As the potential of this attempt increased, a second attempt to establish a group was made at further west at Madikwe, but failed when the susceptibility to Newcastle's Disease killed the group. All these experiences informed development of the current reintroduction plan, which is based around establishing new groups led by wild birds (trained with at the Mabula Group 'bush school' or handed in to rehabilitation centres) and built up with redundant second-hatched juveniles, and thereafter trying to develop neighbouring groups and a stable nucleus for further expansion. The present plan is to test group establishment at new groups at five points across the historic range of the species, from Madikwe in the west (with Newcastle's Disease immunisation), via Thaba Tholo, Mabula and Loskop Dam to Pongola in the east – this is also across an ecological gradient from the drier west to the moister east. On the basis of what is discovered in trying to re-introduce these groups, additional re-introductions will be planned that also attempt to link augmented groups into the re-establishment of a national network of safe and successfully breeding groups.