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 2018
- PhD student Anthony Lowney investigated the importance of Sociable Weaver colonies to the local animal community over a temporal stress gradient. Across the weaver’s range in South Africa and Namibia, he conducted field studies to determine weaver colony importance to the animal community as environment harshness changes.
- BSc Hons student Jess Lund investigated whether Pygmy Falcons lower their body temperature at night to save energy during cold and food stressed winters.
- The Pygmy Falcon population in the study area was monitored for the eighth season. Postdoc Diana Bolopo was investigating how the presence of Pygmy Falcons in a colony is costly for the weavers in terms of behavioural changes, most notably their sleeping hours.
- Our team presented the results of our studies at three international and two national conferences.
- A paper was published on the fledgling body condition of bigger broods of cooperatively breeding Pygmy Falcons in Behavioral Ecology and Sociobiology.
- A paper from Billi Krochuk’s BSc Hons thesis exploring the strange Pygmy Falcon behaviour of lining their nest chambers with faeces was published in Ostrich.
- A BBC documentary ‘Animals Behaving Badly’ filmed at our field site featuring falcon and weaver interactions was first aired in May 2018. A German production team, Text und Bild, also filmed the system this year. Our team members acted as scientific advisers for both crews.
- Diana Bolopo presented at the International Society for Behavioural Ecology conference in Minnesota in August. Anthony Lowney, Billi Krochuk and Robert Thomson presented at the 27th International Ornithological Congress held in Vancouver in August 2018. Robert’s talk was featured by the Cornel Lab of Ornithology as one of the congress highlights.
- Anthony Lowney and Robert Thomson presented at the Annual Meeting of the Raptor Research Foundation in Kruger National Park in December 2018 and they both also attended the 9th Annual Oppenheimer-De Beers Group Research conference in Johannesburg in October 2018.
- Anthony Lowney was awarded the prize for best presentation at the 2018 UCT Department of Biological Science postgraduate research day.
- Our project joined forces with top researchers from WITS, UP, UNISA and UWC to form KEEP (Kalahari Endangered Ecosystem Project) at the Tswalu Kalahari Reserve. This program will incorporate research from a range of taxa to investigate the ecosystem consequences of climate change in the Kalahari. The project, led by Prof Andrea Fuller, has already received sponsorship of two Suzuki field vehicles.
Impact of the project
This project will provide 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; Academy of Finland; Claude Leon Foundation; University of Cape Town launching grant.
Dr Robert Thomson (FIAO, UCT)
Dr Diana Bolopo (FIAO, UCT)
Prof. Michael Cramer (Biological Sciences, UCT)
Prof. Andrew McKechnie (UP)
Dr Luke Arnot (UP)
Dr Dorianne Elliott (UP)
Students: Anthony Lowney (PhD, UCT); Billi Krochuk (BSc Hons, UCT); Jess Lund (BSc Hons, UCT), Ryno Kemp (PhD, UP).
Research Assistants: Melissa Goepfert, Nosipho Mali.