Pied Babblers and Fork-tailed Drongos
Since 2003, Amanda Ridley has maintained a long-term study of habituated Southern Pied Babblers Turdoides bicolor, on the Kuruman River Reserve in the southern Kalahari Desert. Together with her collaborators, Amanda’s work explores the evolutionary ecology of Pied Babblers providing unique insight into conflict and cooperation in societies, life-history strategies and mating systems. In 2006, Amanda began investigating community interactions between Fork-tailed Drongos Dicrurus adsimilis, babblers and other species. Tom Flower joined and greatly expanded the drongo research in 2008, establishing the Drongo Project to study the drongos’ use of false alarm calls to steal food from other animals. Recently, Amanda and Tom have collaborated with Susie Cunningham and Claire Spottiswoode to explore how increasing temperatures will affect the demography of these species in marginal desert environments.
The causes of conflict and cooperation in group-living societies
The Pied Babbler research project investigates the costs and benefits of cooperation in this group-living species. Long-term life history data, along with short-term observations and experiments, have helped us understand the causes and consequences of cooperative breeding behaviour. Group sizes vary according to weather conditions, with the population decreasing when breeding seasons are hot and dry, and during very cold winters.
The range of questions that can be asked increases as the duration of the study grows, and we can now assess life-time fitness. PhD student Amanda Bourne, who graduated in 2020, used the long-term database to understand the impact of heatwaves and drought on survival and reproductive success. We are also investigating the impact of heat on cognitive ability, because cognition is vital to an individual’s ability to behaviourally respond to changes in their environment. PhD student Camilla Soravia is studying the ontogeny of cognition and the relationship between cognition and sociality.
How interactions between species shape animal behaviour
The Fork-tailed Drongo project explores how interactions with other species can shape the evolution of behaviour. Over 40 pairs of individually colour-banded drongos have been habituated. Current research considers the cognitive mechanisms that enable drongos to produce false alarm calls and adjust the calls they use depending on feedback from the target species. Since 2014, we also have studied the impact of climate change on bird persistence in hot desert environments through impacts on foraging behaviour and offspring provisioning. PhD student Ben Murphy is studying how drongos adjust their behaviour to reduce the impact of high temperatures on reproductive success, including through offspring shading, foraging tactics and crepuscular/nocturnal activity. Such behavioural changes may compensate for the costs of missed opportunities when temperatures are high, enabling drongos to adapt to climate change. However, it remains to be determined whether the behavioural adjustments are sufficient to enable drongos to persist in their current range.
Activities in 2020
- Amanda Bourne obtained a PhD for her thesis “Can sociality buffer the impacts of climate change on a cooperatively-breeding bird, the Southern Pied Babbler Turdoides bicolor?”
- PhD student Camilla Soravia completed her second field season on the relationship between heat stress and cognitive performance, testing the hypothesis that increased heat stress leads to cognitive impairment, and hence a limited ability to respond to stimuli in their surrounding environment. COVID-19 put her fieldwork on hold for the 2020/21 field season.
- PhD student Ben Murphy completed his second and third field seasons and is presently collating his data.
- BTech student Lesedi Moagi, working with Amanda Bourne, Andrew McKechnie, Ray Jansen (TUT) and Andre Ganswindt (U. Pretoria), completed the labwork and analyses for her project on faecal corticosterone metabolites (fGCMs) in babblers, showing that these increase at maximum daily temperatures above 38°C, but return to baseline levels the following day, suggesting that hot days represent acute stressors for these birds.
- Three papers on Pied Babblers were published by PhD student Amanda Bourne in 2020. A paper in the Proceedings of the Royal Society B documented the impacts of high temperatures on breeding success; one in Ecology Letters assessed interannual survival, and another in Frontiers in Ecology and Evolution reported compensatory breeding following drought. Taken together, they show that environmental effects are generally stronger than social effects in determining survival and breeding success and that helpers provided limited buffering on survival and productivity under harsh conditions.
- Pied Babbler and Fork-tailed Drongo research was presented at several national and international online conferences, including the Virtual Bird Fair run by BirdLife South Africa, and the online BOU conference BOUSci20: Climate change and birds: solutions to the crisis.
For more details on the collaborative work between the Pied Babbler and Fork-tailed Drongo Projects and the Hot Birds Project, see the Hot Birds Project page.
DSI-NRF CoE grant; Australian Research Council.
Research team 2020
Assoc. Prof. Amanda Ridley (FIAO, UCT and UWA)
Dr Thomas Flower (FIAO, UCT and Capilano University)
Dr Martha Nelson-Flower (U. British Colombia)
Dr Susie Cunningham (FIAO, UCT)
Prof. Claire Spottiswoode (FIAO, UCT and U. Cambridge)
Prof. Andrew Mckechnie (U. Pretoria)
Students: Amanda Bourne (PhD, UCT); Benjamin Murphy (PhD, UCT); Camilla Soravia (PhD, UWA); Lesedi Moagi (BTech, TUT).
Research assistants: Grace Blackburn, Lena Pina Ramirez, Justin Jacobs.