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 group members contribute to territory defence and reproduction, and whether larger groups are more resilient to environmental change. We are also investigating how high temperatures influence breeding success.
The long-term project has provided nest boxes to 20 ground-hornbill groups in the Associated Private Nature Reserves, adjacent to Kruger Park. Together, these groups make 12-15 breeding attempts each year. This population has now become one of the strongholds of the country and this successful population is now dispersing outside of these reserves where they have begun to re-populate 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.
PhD student Kyle-Mark Middleton, supervised by Rita Covas, Claire Spottiswoode and Fanny Rybak, is studying the hornbill’s social structure and individual contributions to breeding and territory defence. Kyle is comparing different groups’ dawn choruses and using play-back experiments to determine if the birds recognise different groups. He also is using camera traps at the nests to obtain insights into the hornbills’ private lives, and is analysing long-term data to investigate the environmental and social factors affecting breeding performance.
PhD student Carrie Hickman, supervised by Rita Covas and Susan Cunningham, is 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 assessing threshold temperatures by recording birds behavioural responses to high temperatures. iButtons 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 2022
- Kyle completed his PhD thesis. His analyses showed that different groups have unique vocal ‘signatures’, with males producing lower frequency calls than females. Deep learning algorithms correctly classify 90% of female territorial calls to an individual bird. The territory defence results showed that during territorial intrusions, larger territory holding groups were more likely to approach intruders than smaller groups. The identity of the intruders had no effect on the response of territory holders. Results on nest provisioning showed that the efforts of individuals were associated with their age, and that high temperature had a negative effect on these efforts.
- Kyle began working for the Mabula Ground-Hornbill Project, allowing him to continue working and researching the birds within the APNR and assisting Carrie in her research.
- In February 2022 Carrie upgraded to a PhD, incorporating additional questions which aim to investigate important threshold temperatures for adult birds and whether females adjust maternal allocation according to environmental and social conditions.
- Carrie established WhatsApp groups for field guides and rangers to submit sightings of the birds and has been using citizen science data from Kruger National Park in order to obtain data on behaviour, microsite use and group movements.
- Carrie constructed black bulbs which were deployed in different microsites in order to obtain operative enviromental temperatures for ground-hornbills (the thermal load experienced by the birds).
- Working with a conservation student, Carrie conducted a survey in Timabvati Private Nature Reserve, collecting information on shade availability in an area that is representative of a ground-hornbill group territory. This will be repeated in winter to determine the difference in shade availability between the seasons.
- Carrie has continuing to weigh and measure nestlings at specific ages to obtain growth rates. She also analysed iButton data which will be used to improve the design of artificial nests.
- Ongoing repairs to and replacement of artificial nest boxes ensured that ground-hornbills can continue to thrive in the study area, which has few natural nest cavities.
- In December 2022 four redundant second hatched chicks were removed from nests in the APNR and transported to the MGHPs rearing facility at Loskop Dam.
- Kyle completed his PhD thesisvand qualified for graduation in March 2023.
- In October 2022 Carrie and Kyle attended the African Bioacoustics Conference in Skukuza, Kruger National Park. Kyle won the award for best presentation.
- In November 2022 Kyle attended and presented at the Pan African Ornithological Conference in Livingstone, Zimbabwe.
- Carrie was awarded a second grant for her research from the Rufford Foundation.
- The 2021/22 breeding season saw seven chicks fledge from 13 nests.
- The 2022/2023 breeding season started well with 15 breeding attempts, the last time the project saw this number of attempts was in 2011.
- Predation events from a leopard and a genet were recorded on camera traps.
- Four chicks were harvested for the reintroduction programme.
- Four new nests were placed outside the study site to encourage natural dispersal.
- A new group of three birds became extablished in a new artificial nest and attempted to breed, but unfortunately abandoned the nest before chick hatching. The female was identified from her colour ring as a bird that was ringed as a nestling in 2012, from a nest >10km away. This is the first recorded recruitment event for the population.
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.
DSI-NRF CoE grant; 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 in Africa; Wild Wonderful World; Blue Skye Society Trust.
Research team 2022
Dr Rita Covas (FIAO, UCT and CIBIO, U. Porto)
Prof. Claire Spottiswoode (FIAO, UCT / U. Cambridge)
Dr Fanny Rybak (U. Paris-Sud, France)
A/Prof. Susie Cunningham (FIAO, UCT)
Students: Carrie Hickman (PhD, UCT); Kyle-Mark Middleton (PhD, UCT).