Southern Yellow-billed Hornbill

The southern yellow-billed hornbill (Tockus leucomelas) is a small, slender hornbill of southern Africa, about 40 cm long. Males weigh roughly 153–242 g and females about 138–211 g. The long yellow bill is the most obvious feature. Males have a broader bill and a more developed low casque, the small raised structure along the top of the bill, while females are slightly smaller. The plumage is strongly patterned black and white, with a pale head and conspicuously spotted wings.

The very similar eastern yellow-billed hornbill (Tockus flavirostris) has blackish rather than reddish skin around the eye and generally a less densely spotted wing pattern. Two subspecies are generally recognised; most birds in southern Africa belong to T. l. leucomelas.

Southern yellow-billed hornbills are characteristic of dry savanna, thornveld, open woodland and semi-arid scrub. They are especially common where scattered trees provide roosts and natural cavities for nesting, while open ground and low vegetation give easy access to prey on the ground.

In the western parts of the range they also enter very arid country, whereas dense forest is generally avoided. The species is therefore strongly associated with warm, open landscapes rather than closed forest.

Invertebrates dominate the diet. Ants and termites can be especially important during the dry season, while grasshoppers, beetles, caterpillars, centipedes, scorpions and other ground-dwelling invertebrates are also eaten. Small vertebrates are taken when the opportunity arises, and fruit and seeds supplement the animal diet.

Most food is found while walking or running on the ground or moving through low bushes, with prey picked from the surface and low vegetation rather than by digging deeply into the soil.

Southern yellow-billed hornbills are generally resident and territorial and are most often seen in pairs or small family groups. A pair commonly leaves a regular night roost in the morning, spends much of the day feeding on the ground and returns to roost toward evening.

In the driest parts of the range, birds may move locally when food becomes scarce, especially after prolonged dry periods. These movements normally remain within the region rather than developing into long-distance migration.

Like many other hornbills, the southern yellow-billed hornbill nests in a sealed tree cavity. The female closes herself inside a natural hollow, leaving only a narrow slit through which the male passes food. She usually lays three or four eggs, although clutches of two to six are known, and incubates them for about 24 days while the male supplies food.

The female leaves the cavity when the oldest chick is roughly 19–27 days old. The chicks then reseal the entrance and remain protected inside while both parents bring food. They normally stay in the nest for about 42–47 days after hatching and remain close by for a few more days before following their parents on feeding trips. Sealing the nest helps protect the young from many predators, but it also makes the female and chicks strongly dependent on a steady food supply from the male.

Extreme heat can disrupt this system. In a long-term study in the southern Kalahari, the proportion of breeding attempts that produced at least one fledgling fell from 58% in 2008–2011 to 17% in 2016–2019. All breeding attempts exposed to the most persistent heat conditions failed. In very hot weather, males spend more time panting to lose heat and less time finding food, while the female and chicks inside the cavity still depend on regular food deliveries.

The southern yellow-billed hornbill is globally classified as Least Concern on the IUCN Red List. It remains widespread and common in many suitable savanna and open woodland habitats across southern Africa.

Extreme heat and drought can nevertheless reduce breeding success sharply in the hottest parts of the range. The southern Kalahari population shows how continued warming could place increasing pressure on hornbills living in already hot, dry environments.