A preliminary investigation into the status, distribution and some aspects of the foraging ecology of the southern ground hornbill (Bucorvus cafer) in Natal.

Abstract

A study on the distribution, status and selected aspects of the foraging ecology of B. cafer in Natal, was undertaken from January 1989 to December 1990. A census was initiated to assess the distribution of B. cafer in Natal. 436 sightings were reported from 187 locations. B. cafer occurs throughout Natal, except in the far northwestern regions. A population estimation based on this census suggest that between 300-350 B. cafer individuals exist in Natal, excluding KwaZulu regions. The large area occupied by KwaZulu and the protection of this species by Zulu folk law, suggest that the population may be considerably larger. Selected aspects of the foraging ecology of the two study groups in the Natal midlands were examined, focusing on the role that individuals play in provisioning the nestling, nest bound female and fledgling. B. cafer are predominantly carnivorous. They are able to utilise habitats used for a wide variety of agricultural

practices. The major criteria, in terms of habitat selection, being a short (0.5 m) or sparse ground cover. Younger birds were less successful than older individuals at digging and probing for food. Foraging success rate of the juvenile increased from 7.2% prior to nesting, to 51.2% during nesting. The acquisition of foraging skills, particularly digging and probing, takes time and experience. Frogs were the major food item fed to the nestling and nest bound female. The presence of helpers reduced the amount of feeding by parent birds. Helpers in the stainbank group supp plied 25% of food bundles to the nest. The juvenile did not act as a helper. Subadults helped most during the periods when the demand for food delivery to the nest was highest, and at the end of the nesting period. Helpers reduced the amount of time that the dominant female spent away from the nest during incubation and early nestling phase. Once the female left the nest, the male reduced his food delivery rate. An abundance of frogs, close to the nest, enabled a single pair to adequately provision a nestling. The parent birds provisioned the fledgling until the following breeding season.