The Southern Ground-hornbill (Buvorcus leadbeateri), “SGH” from here on, is endemic to Africa and has been recorded in 16 African countries, these are: South Africa, Namibia, Botswana, Zimbabwe, Zambia, Mozambique, Malawi, Angola, Democratic Republic of Congo (DRC), Rwanda, Burundi, Kenya, Uganda and Tanzania. Ground-hornbills are resident, occurring from sea-level to altitudes of 3000 metres on fixed, firmly defended territories that range in size between 100 – 250 km ² in savanna, grassland and open woodland. Open habitats with a short grass layer are ideal for foraging within these areas.
Ground-hornbill 101
Ground-hornbills are striking, large birds found only in Africa and are known for their distinctive appearance and intriguing behaviour.
The Southern and Abyssinian Ground-hornbills are the only two species in the genus Bucorvus, classified under the order Bucerotiformes in the family Bucorvidae, a unique sister clade which diverges from the Bucerotidae, otherwise known as nest-sealing hornbills. The Bucerotiformes originated in Africa and following phylogenetic divergence, spread out and eastward to South Asia, South-East Asia, and marginally Australasia to evolve further. Some members of Tockus, and Buvorcus families on the other hand, remained in Africa. Tectonic and climatic changes then proceeded to split up the ranges on both the African and European landscapes even further.
Ground-hornbills are faunivorous and have quite a varied diet. They both hunt and scavenge but unlike many other meat-eating avian species, they do not use their feet to catch their prey: they have no talons, their claws are short from walking in the grass all day. Rather, their beaks are weapons and tools.
They feed on a wide range of arthropods (insects and arachnids), reptiles (snakes, lizards and tortoises), amphibians (frogs), small birds, and small mammals up to the size of a hares. Tortoise shells are no match for their powerful blows, and they are very adept at hunting venomous snakes. They have been observed picking ectoparasites from the hides of African warthogs and impala, and on the odd occasion, even feed on fruit or seeds.
Southern Ground-hornbills are the largest known cooperatively breeding bird species in the world, with groups consisting of one dominant male and female and non-breeding helpers, mostly in the form of previous sons that delay dispersal from their natal territory to help care for future chicks, since the raising of young is demanding in this species. Copulation is strictly between the alpha pair, and only one adult female is usually tolerated in a group.
Slow Breeding Rate
A critical aspect of Southern Ground-hornbill biology is their slow breeding rate and their low chick recruitment. They breed only once during the wet season in the summer from September to December. Whether or not the group breeds depends heavily on environmental suitability, body condition, and whether they have an available nest. They are likely to skip that year if there are unusual weather patterns or the rains arrive late (which, in turn, would mean less food available in the bush around nesting time). Several years can occur between breeding, and the overall fledgling average is one chick per group every nine years. In 80% of clutches the female lays two eggs in the nest, three to five days apart. This results in the chicks hatching at different ages, and the older chick outcompeting the younger sibling on most occasions. The group only ever raises one chick, the second is simply ignored by the adults and succumbs to dehydration within a number of days. The laying of a second egg has been hypothesied to be a backup in case the first does not survive. Otherwise, ground-hornbills will not rear the second chick, even when the food supply is steady.
Southern Ground-hornbills take 4-6 years to reach their full size and mature colouration. Until that time, the juvenile will be protected and fed by the adults. Female chicks are cast out from the group around 2 years of age, and must wander alone to find another group that does not have an alpha female.
Southern Ground-hornbills live in dynamic hierarchical family groups of two to twelve birds, the average being 4 or 5. Larger groups have been reported in their more northern range, but it is very uncommon. They are territorial, inhabiting ranges of roughly 100km2, and will live in the same area and use the same nest for generations. In areas with a thriving Southern Ground-hornbill population, the territories lie adjacent. The species has a proclivity for natural dispersal: every so often, a male helper leaves or is rejected by the others in the group, and wanders alone until he finds another group to join. These dispersals between neighbouring territories maintain gene flow for a healthy population.
The Southern Ground-hornbill is unanimously revered as the thunderbird or rainbird across much of its sub-Saharan range in part, perhaps, because its distribution coincidentally matches that of the Bantu-derived languages and an ancient language-linked belief. However the cultural significance, although always rain-related, is not the same for each area or tribe, which results in subtle differences that have very different conservation results. In Zimbabwe for example, both Ngoni Chiweshe and Rob Bruyns have documented a striking difference in protection afforded the species between predominantly ChiShona and Sindebele speaking areas.
In isiZulu-speaking communities of South Africa, the thunder bird (iNsingisi) is respected for its ability to kill snakes, even highly venomous ones, rats and cattle ticks. It’s primary power, however, is that it forecasts good rains, and is even able to summon rains in times of drought. This is due to the bird’s breeding biology, which is tightly synched to the first decent rains of the season, and also, being such a long-lived bird, if the rains are not sufficient to provide for a hungry chick then it is no big deal for the group to skip a year and wait for better conditions. This ability was reported to be so powerful that, when putting a ground-hornbill feather in a river bed to summon the rains, if one did not weigh it down with a rock so it was able to be retrieved once the drought had been broken, floods might ensue.
It appears that the role of ground-hornbills (iNtsikizi) in some isiXhosa-speaking areas may be slightly different, where the birds are hunted with dogs solely to obtain a specimen for placement in a dry river bed in times of drought. This was revealed at the Keiskamma Arts Project, which has captured this value of the ground-hornbills in times of drought in a six-panel tapestry, designed by artist Cebo Mvubu in the style of the “the Unicorn Tapestries“. This modern masterpiece took seven artists, six felters and 24 embroiderers an estimated 2 600 hours to complete.
It may be though that this subtle difference between belief systems – a feather versus an entire carcass – would have a profound effect on the population and regional conservation biology of the species. The use of a whole carcass, especially if an alpha male or female is captured, puts the remaining group at risk, as ground-hornbill juveniles depend on the teachings of more experienced birds in the group for all manner of behaviours: hunting, roosting, courtship and predator avoidance.
As our research developed we realised more and more that we need to strengthen and support this cultural protection, and it has been our honour to have Zulu Prince Mangosuthu Buthelezi, honour the conservation work of ground-gornbills by becoming the patron of the birds.
