Sociable Weaver nests as a resource
This project examines the importance of Sociable Weaver Philetarius socius nests to Kalahari animal and plant communities. The objectives are to investigate the diversity of animals associated with the nests, the interactions between these species, and to gain insights into the life histories of associated species. We also aim to understand how the ‘ecological engineer’ potential of these nests may have community-wide impacts on structure and function, and how this impact may change across environmental gradients.
Evidence of the importance of facilitation in communities has accumulated, which challenges traditional emphasis of negative interactions in ecology. In particular, facilitative interactions are predicted to increase in importance in stressful environments and may become a crucial component of the adaptive responses of communities under stress. Ecological engineers – species that modify habitats and ameliorate abiotic stress for other species – are a key research focus. Identifying and understanding the impact of ecological engineers is vital, especially in arid environments that are expected to become harsher with global climate change.
Pygmy Falcons Polihierax semitorquatus are the most controversial user of the weaver colonies. They never construct their own nests, depending entirely on weaver colonies, which is a unique obligate nesting association. Pygmy Falcons also, albeit rarely, prey on weaver nestlings and even adults, suggesting a semi-parasitic relationship between the species. We aim to describe the natural history and ecology of Pygmy Falcons, and to characterize their interactions with Sociable Weavers; do falcons provide benefits to weavers or are they vertebrate parasites?
Activities in 2019
- Two new PhD students, Olufemi Olubodun and Timothy Aikins Khan, started in the project in the second half of 2019. Olufemi is investigating various aspects of the life history of African pygmy falcons. Timothy is investigating the costs and benefits to Camelthorn Vachellia erioloba and Shepherd’s trees Boscia albitrunca from hosting Sociable Weaver colonies.
- The project hosted the field camp of the Fitz’s Conservation Biology Master’s programme. Thirteen MSc CB students spent a week at Tswalu Reserve in the Kalahari where they collected a range of data related to the impacts of Sociable Weaver colonies on plant and animal communities.
- The Pygmy Falcon population in the study area was followed for the ninth season. Olufemi has been monitoring their breeding success and group compositions.
- Data collection towards the KEEP (Kalahari Endangered Ecosystem Project) collaboration with WITS, UP, UNISA and UWC researchers started in earnest. These long-term data will contribute to identifying the impacts of climate change on the Kalahari ecosystem.
- Our team presented the results of our studies at one international and one national conference.
- We published an article entitled ‘Helpers improve fledgling body condition in bigger broods of cooperatively breeding African Pygmy Falcon’ in Behavioural Ecology and Sociobiology with Diana Bolopo as first author.
- Jess Lund’s BSc Hons thesis investigating winter thermoregulation in free-ranging Pygmy Falcons won the award for best UCT Biological Sciences dissertation in 2018.
- Anthony Lowney submitted his PhD thesis and is currently awaiting the evaluation of the reviewers.
- Robert Thomson and Diana Bolopo presented papers at the European Ornithological Union Conference in Romania.
- Anthony Lowney presented a paper at the 10th Oppenheimer Conference in Johannesburg.
Impact of the project
This project is providing unique insights into the community ecology and between-species interactions in the Kalahari. It will quantify the ecological engineering role of the Sociable Weaver and potentially determine the role of Sociable Weaver nests in a warming and increasingly arid Kalahari. The outputs of this project will also contribute to available eco-tourism information that enhances the experience of visitors to landscapes within the distribution of the Sociable Weaver.
DST-NRF CoE grant; Tswalu Foundation; University of Cape Town launching grant, Suzuki South Africa.
Research team 2019
Dr Robert Thomson (FIAO, UCT)
Dr Diana Bolopo (FIAO, UCT)
Prof. Michael Cramer (Biological Sciences, UCT)
Prof. Andrew McKechnie (U. Pretoria)
Dr Luke Arnot (U. Pretoria)
Dr Dorianne Elliott (U. Pretoria)
Billi Krochuk (UBC)
Students: Timothy Aikins Khan (PhD, UCT); Anthony Lowney (PhD, UCT); Olufemi Olubodun (PhD, UCT).
Research Assistant: Rion Cuthill.