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 Southern Ground-Hornbill groups in the Associated Private Nature Reserves (APNR) area adjacent to Kruger Park, to compensate for the scarcity of suitable natural tree cavities. Across these groups, 12–15 breeding attempts occur on average per year. This area is now a national population stronghold for the species and this successful population is now dispersing outside of the APNR and repopulating 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. 

Postdoctoral research fellow Dr Kyle-Mark Middleton is 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 have been deployed to track the movements of birds within their territories. Additionally, perch scales (developed by students from UCT’s Department of Electrical Engineering) and camera traps have been implemented at nesting sites to automatically monitor the body condition of various individuals. 

In 2025, PhD student Carrie Hickman, supervised by Dr Rita Covas and A/Prof. Susie Cunningham, completed her research investigating the impacts of high temperatures on behaviour, reproduction and offspring development in Southern Ground-Hornbills. This research also tested whether larger groups, with more helpers contributing to offspring care, can buffer the negative effects of high temperatures on reproduction. Findings from this research are being used to inform improved nestbox design, habitat management, and the identification of landscapes and microsites where temperature increases are slower, thereby improving the species’ chances of persistence under future climate warming. 

Activities in 2025

  • Carrie Hickman finished her data collection in April 2025, adding an additional 11 breeding attempts (nine fledged chicks) to her data.  She completed her writeup and submitted her PhD thesis in January 2026.
  • Leg-ring tracking devices, specifically designed for Southern Ground-Hornbills, were placed on eight chicks prior to fledging in March/April. Out of these eight individuals, six survived the year and the devices have exceeded expectations, providing GPS data every five minutes. Because juveniles remain within their natal groups for some time (several months to years) this tracking information provides valuable information on group territories and how the birds use the landscape.
  • Four automatic perch scales were deployed in October at nest sites to weigh adult birds when they visit the nest. The scales automatically store mass data when a bird lands on the perch, and the identity of the individual is simultaneously recorded by a camera trap. The scales successfully recorded the mass of several birds; however, adjustments are required to make the scales more robust. These adjustments will be made in early 2026.
  • In September, Kyle, Carrie, Rita and Susie attended and presented at the Hot Birds Research Project biennial retreat, which was held at The Royal Malewane Research and Conservation Centre in Thornybush Private Nature Reserve.
  • A new natural nest was found, with a nestling, on Moditlo Game Reserve (~20 km from the APNR study site). The adults in the group, which were identified from their SAFRING rings, had hatched and fledged from artificial nests in the APNR.
  • Kyle presented his work and some of Carrie’s PhD findings in a Learn the Birds webinar in December.
  • Three second-hatched chicks were harvested from nests in December and transported to the MGHP rearing facility at Loskop Dam. They will be reared and later released to help reestablish wild populations.
     

Highlights

  • Kyle’s paper on the impacts of hot weather on reproductive outcomes in Southern Ground-Hornbills was accepted in the journal American Naturalist and will be published in 2026.
  • The project successfully secured funding from the Rufford Foundation (a Rufford Small Grant awarded to Kyle for his postdoctoral work), as well as from the APNR, Wild Wonderful World and several private donors.
  • During the 2024/25 breeding season, nine chicks fledged from 11 breeding attempts, six of which survived the year. The 2025/26 breeding season began well, with 15 breeding attempts recorded. However, the devastating floods that affected the study area in January 2026 may have impacted breeding success. Assessment of these effects will only be possible once access to nest sites is restored.
     

Impact of the project
This project continues to generate fundamental knowledge about the species, the factors affecting reproduction, their social structure and their behaviour and 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 becoming established in areas previously lacking ground-hornbills. In collaboration with the Hot Birds Research Project, this research also contributes to a broader understanding of climate change impacts, informing conservation strategies for this and other savanna species, and it informs 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; The Rufford Foundation; Mary Oppenheimer & Daughters Foundation; John Solomon and Caroline Buckway; Wild Wonderful World; Bruce and Judy Neill.

Research team 2025
Team leaders and collaborators:
Dr Kyle-Mark Middleton (FIAO, UCT)
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)

Student:
Carrie Hickman (PhD, UCT).

Research Assistants:
Ryan Forbes, Quim Agell