Southern Ground-Hornbills Bucorvus leadbeateri are large, group-living birds that require extensive territories with large trees for breeding and roosting. Habitat loss has led to a two-thirds reduction in their range in South Africa during the past century. A long-term study has investigated their habitat use, breeding success, and dispersal. Now we are studying how high temperatures influence breeding success and nestling growth rates. We are also investigating how high temperatures influence micro-habitat use, behaviour, and body condition year-round.

The long-term project has provided nest boxes to 28 ground-hornbill groups in the Associated Private Nature Reserves (APNR), adjacent to Kruger Park. Together, these groups make 12-15 breeding attempts each year. This area is now a national population stronghold for the species and this successful population is now dispersing outside of the APNR and is re-populating the surrounding area. The project also provides second-hatched chicks (which invariably die of starvation in the wild) to the Mabula Ground-Hornbill Project (MGHP) for captive-rearing and later release. Post-doctoral research fellow Dr Kyle-Mark Middleton has started investigating how temperature influences habitat use and trade-offs between thermoregulation and other vital behaviours (foraging and vigilance) year-round, and how these trade-offs will in turn affect body condition and reproduction. Newly developed leg ring tracking devices will be implemented to track the movements of birds within their territories. Additionally, perch scales (being developed by UCT’s engineering department) and camera traps will be implemented at nesting sites to automatically monitor the body conditions of different individuals.

PhD student Carrie Hickman, supervised by Rita Covas and Susan Cunningham, continued her work investigating whether high air and nest temperatures impact hornbill nestlings by measuring nestling growth, fledging size and telomere length (a measure of physiological condition). She is also recording the hornbill’s behavioural responses to high temperatures. iButtons (devices used for data logging) have been installed inside nests to obtain hourly temperature recordings and camera traps are used to record provisioning. The results from these analyses will assist in designing better nest boxes for the species and provide information on locations where the birds will have the best chance to persist, where microsites are more favourable and temperature increases are slower.

Activities in 2024

  • PhD student Carrie Hickman successfully carried out another field season, where nine ground-hornbill nestlings fledged in February and March 2024. Carrie weighed and measured nestlings at specific ages to obtain growth rates, adding to her dataset on nestling growth and physiology.
  • Kyle repaired and replaced artificial nest boxes to ensure that ground-hornbills continue to thrive in the study area, which has only 5 natural nests out of a total 36.
  • Leg-ring tracking devices, specifically designed for ground-hornbills, were designed and tested on a captive bird. This test was successful and the trackers will be implemented in 2025.
  • New artificial nests were designed and installed. The wooden design ensures that external temperatures are buffered, and also have provisions for future research, including hidden compartments to install equipment for internal nest cameras and scales.
  • A new website for the project was created to help provide information on the research and conservation activities carried out by the project participants.
  • The project hired a field assistant, Ryan Forbes, at the end of 2024 for the breeding season. Ryan will be assisting with fieldwork duties as well as data capturing and analyses.

Highlights

  • The 2023/24 breeding season saw nine chicks fledge out of 14 breeding attempts and the 2024/25 breeding season started well with 11 breeding attempts.
  • A ringed individual was resighted outside of the study site. This individual was photographed and its ring number identified. The individual fledged from a nest in 2011 within the study site and dispersed approximately 40km where it has now joined a new breeding group.
  • Six new nests were placed outside the study site to encourage natural dispersal.
  • Nine nests were installed to replace nests that had either been destroyed or fallen down.
  • New colour rings were implemented to help identify individual birds within the study site.
  • New tracking device rings were developed specifically for ground-hornbills.
  • Continued research on ground-hornbill vocalisations indicated that the provisioning vocalisations differ based on whether males bring vertebrate or invertebrate prey to the nest.
  • An adult breeding female was seen with what appeared to be a broken leg. This resulted in the nestling within the nest being in poor condition and covered in ectoparasites. With the assistance of local vets, this nestling was given antibiotics and fluids which subsequently led to its successful fledging.
  • A sick bird was found within the reserves next to a landowner’s home. It is suspected that the bird ate window putty laced with parafin. This bird was collected, treated at Onderstepoort veterinary hospital, and then released back into the study site several weeks later.
  • The population size in the study site was estimated to have roughly tripled in the past 25 years.
  • Kyle-Mark Middleton rejoined the project as a Post-doctoral Research Fellow

Impact of the project
This project continues to generate fundamental knowledge about the species, the factors affecting reproduction, their social structure and their physiology. It also contributes to the population growth of Southern Ground-Hornbills in the APNR and has demonstrated the efficacy of artificial nests as a conservation tool in areas where natural cavities are scarce. The surrounding areas are now beginning to benefit from the project, with new groups occurring in areas previously lacking ground-hornbills. The project contributes to the national Southern Ground-Hornbill Species Action Plan and the Southern Ground-Hornbill Reintroduction Plan.

Key co-supporters
The Foundation for Science and Technology (FCT), Portugal; Associated Private Nature Reserves; National Geographic Society; The Rufford Foundation; Mary Oppenheimer & Daughters Foundation; John Solomon; Timothy Hancock Charitable Trust; Wild Wonderful World; Bateleurs.

Research team 2024
Team leaders and collaborators:
Dr Rita Covas (FIAO, UCT / CIBIO, U. Porto)
A/Prof. Susie Cunningham (FIAO, UCT)
Prof. Claire Spottiswoode (FIAO, UCT / U. Cambridge)
Dr Fanny Rybak (U. Paris-Sud, France)
Dr Kyle-Mark Middleton (FIAO, UCT / Mabula Ground- Hornbill Project)

Student::
Carrie Hickman (PhD, UCT).

Research Assistant:
Ryan Forbes