letting nature back in

Here is the first in a series of posts on terrestrial birds, defined rather loosely as those species that spend most of their time foraging on the ground, rather than in trees or hunting on the wing. First up is the southern ground hornbill (Bucorvus leadbeateri).

I have seen wild ground hornbills in conservation areas in savannah and in open woodland, and even glimpsed them in fallow agricultural lands in the Midlands of KwaZulu-Natal.

Most sightings have been of pairs or small family groups walking slowly and seemingly methodically, foraging for prey. The two in the photo above were part of a small group that we saw in Kruger National Park. As indicated by their common name, ground hornbills spend much of their time foraging on the ground. They have elaborately long eye lashes to protect their eyes from dust and vegetation.

The large bill is a formidable and deft weapon for catching and subduing invertebrates as well as small reptiles, birds and even mammals if they can catch them. They are known to accumulate several prey items, as in the photo above, that they carry in the bill to improve their foraging efficiency. They will take the items to eat in the safety of a more secluded space or else take them to feed to the group’s breeding female and/or her chick.

Southern ground hornbills also eat carrion. Sadly, this practice frequently results in lead poisoning as the remains, including discarded offal, of animals that have been shot with lead bullets are contaminated with lead that can become fragmented throughout the body. Southern ground hornbills are particularly susceptible to lead poisoning. A coalition of organisations has formed a Lead Task Team to work towards reducing the poisioning of wildlife by lead and promoting the use of alternative ammunition that does not contain lead.

Another risk for scavengers, including southern ground hornbills, is consuming carcasses of animals and birds that have been deliberately poisoned as they are regarded as pests. For more on poisoning threats click on this link: https://ground-hornbill.org.za/mitigate/

The large bill, including the casque, and the bare skin on the face and the bare loose skin at the throat, help with thermoregulation through heat dissipation in hot weather. By adjusting blood flow when in hot conditions, the birds are able to radiate heat from the bill and bare skin areas.

The loose skin (gular pouch) at the throat serves another function too; it is inflated to amplify the bird’s loud booming call that can be heard over long distances, up to several kilometres (miles) away. The calls help maintain contact between group members while foraging, and also advertise their territory. Pairs call at dusk and at dawn to proclaim their territory in a rhythmic duet. To hear and see a pair calling, see https://ground-hornbill.org.za/ground-hornbill-101/ and select “Sounds”. As can be seen in the video, the female can be distinguished by the purple patch at the throat, whereas the male’s throat is uniformly red.

Although ground hornbills occur naturally in hot regions, they are nevertheless intolerant of prolonged high temperatures, and in addition to thermoregulating via the bill and the bare skin areas, they also may use other means to deal with the heat: they retreat to the shade, become less active, start panting, find perches off the ground and/or droop their wings to allow air to circulate around the body.

With climate change, temperatures are increasing in both summer and winter. Like many other birds and creatures in already hot regions, the increased temperatures make it difficult for them to remain active enough to forage for long-enough periods of time to find sufficient food, which in turn threatens attempts at breeding and breeding success. In winter, prey can be scarcer and there is less available shade, so needing to forage for longer with fewer opportunities to find shade is ever more stressful in generally hotter winters.

The largest species of hornbills worldwide, southern ground hornbills are approximately turkey-sized and may weigh anything from about 2–6.2 kg (4.4–13.6 lbs) with the males mostly being larger than the females. Although they forage by walking on the ground, they are capable of flying. Revealing their white covert and primary wing feathers while flying, and with a wingspan of 1.2–1.8 m (4–6 ft), they are impressive in flight.

Ground hornbills are long-lived, with life expectancy in the wild being 40–50 years, and up to 70 years in captivity. With such longevity, they reach sexual maturity only at 4–6 years, usually breeding for the first time when they are about 10 years old.

Although foraging exclusively on the ground, southern ground hornbills do roost and nest in trees. We saw a small family group in a large and solitary marula tree when we were on a visit to Kruger National Park in 2021. Ground hornbills are cooperative breeders living in small territorial family groups with one dominant breeding pair and a number of non-breeding helpers.  In the above photo, the two on the left turned out to be the breeding pair. The adult on the left is one of the helpers, and not pictured is a fourth member of the group, an immature bird yet to gain its adult colouration.

Up in the tree, the adult helper stretched his wings and showed off the white wing feathers that are normally concealed. Most of the helpers in a family group are males as the females disperse or are chased from a family group before they reach sexual maturity. They wander alone until they find a group to join up with. Males remain in the family group as helpers, even after reaching sexual maturity, with some individuals eventually dispersing to join other groups.

Despite living in cooperative groups, southern ground hornbills have a very slow breeding rate. Breeding attempts are affected by several factors, including environmental conditions and weather patterns, the body condition of the birds, and whether or not they have an available nest, meaning that several annual summer breeding seasons may pass without them breeding at all. According to the Mabula Ground Hornbill Project, the overall fledgling average is only one chick per group every nine years.  

Southern ground hornbills nest in cavities in large trees, but may also find nesting sites on rock faces or earth banks. Unlike other hornbill species, the female is not sealed up in the nest, but she does incubate the eggs in the nest (over a period of 40 days) and mostly stays with the newly hatched chick/s for over a month. She does, however, leave the nest daily to join the others in the group and participate in territorial calling. The entire group contributes to bringing food to the nesting female and to the chick prior to it fledging.

Although ground hornbills typically lay two eggs several days apart, resulting in an older and younger chick, it is only the elder chick that is raised. The younger bird is thought to be a “spare” that will be raised if the first egg fails or the older chick does not survive. So, usually the younger chick ends up dying of starvation.

Classed as Endangered in South Africa and Namibia (and classed as Vulnerable in their range in central and eastern Africa), several projects actively intervene in the conservation of this species that is exposed to many threats. In response to the rapid decline in the numbers of ground hornbills in southern Africa, the Mabula Ground Hornbill Project, founded in 1999, works to protect and conserve the species. As part of their work in restoring ground hornbill populations, the project harvests the redundant second chick (if left in the nest it would perish from starvation) from the nests of wild southern ground hornbills. The chicks are hand reared at a rehabilitation centre. Each chick over time is carefully integrated into a group led by a wild breeding male/alpha male. For a description of this complex process click on this link: https://ground-hornbill.org.za/restore/

In the photo above the breeding pair are looking particularly regal perched in the marula tree just prior to mating. The female, in the foreground, can be distinguished by the purple patch of skin at her throat. I don’t know whether this tree in which they are perching will ultimately become their nesting tree.

Unfortunately, along with habitat destruction and other threats, naturally occurring nesting sites have become increasing rare. The APNR Southern Ground-Hornbill Project is a conservation project in the greater Kruger area. The Associated Private Nature Reserves (APNR) are five privately owned nature reserves on the western boundary of the Kruger National Park. A key focus of the project is the installation and monitoring of artificial nests, which have significantly contributed to more frequent breeding activity and improved breeding success. The project’s research and monitoring data contributes also to the work of the Mabula Ground Hornbill Project and the national strategy for conserving this species. For more information on the success of the artificial nests click on this link: https://www.apnrgroundhornbillproject.com/projects

While we were watching, the female moved to an outer branch and called a few times before returning to the male.

Both birds then hopped up onto a higher branch.

The pair then mated while high up in the tree. We only had a limited view of them as they were partially concealed by branches.

At one point the female tipped forward at a dangerous angle but the pair managed not to fall out of the tree.

Meanwhile the juvenile on the ground below the tree watched the mating pair, most likely his parents, with what looked to be a disconsolate air. We rather fancifully imagined that he was having a premonition of his losing his current favoured “baby” status, and maturing into the status of helper to the group and to the breeding pair and any ensuing offspring.

After mating the pair remained together and indulged in a bit of preening. After a few minutes the juvenile flew up into the tree just below them, and the other adult male remained in his perch higher up in the tree.

This was a very special sighting of this iconic species. It is sobering to know that the numbers of these birds have declined rapidly in the face of threats that include habitat loss, poisoning, electrocution on power lines, deliberate persecution and climate breakdown. At the same time, it is heartening to know of the active conservation projects that work to mitigate these threats. For more about these projects see the links in the sources listed below.

When driving away, after an engrossing time watching this hornbill family, we stopped to look back at the roosting tree that was not far from the road. All four birds were perched high up in the branches. Let’s hope that they had breeding success after the mating we witnessed, and that the descendants of this family continue to survive despite the many threats and challenges. By now, if he has survived, the juvenile would be about ten years old and of breeding age, possibly having dispersed to a new group and attaining breeding status.

Sources:

🔖Africa Geographic. 2022. Southern ground hornbill: Africa’s rara avis. https://africageographic.com/stories/southern-ground-hornbill-africas-rara-avis/#:~:text=It%20is%20the%20voice%20of,Africa’s%20most%20iconic%20bird%20species.

🔖APNR Southern Ground-Hornbill Project. 2025. https://www.apnrgroundhornbillproject.com/

🔖BirdLife International. 2025. Species factsheet: Southern Ground-hornbill Bucorvus leadbeateri. https://datazone.birdlife.org/species/factsheet/southern-ground-hornbill-bucorvus-leadbeateri

🔖Janse van Vuuren, Andries & Kemp, Lucy & McKechnie, Andrew. 2020. The beak and unfeathered skin as heat radiators in the Southern Ground‐hornbill. Journal of Avian Biology. 51 (6). DOI:10.1111/jav.02457

🔖Mabula Ground Hornbill Project. 2024. https://ground-hornbill.org.za/what-we-do/

Posted by Carol