Global change and urban birds
Anyone who has spent time at the University of Cape Town will know about the Red-winged Starlings Onychognathus morio on Upper Campus. These birds have developed a reputation amongst the UCT community for being sly, lunch-thieving pests and many students can recount a story of having a starling swoop past their heads on Jammie Plaza in pursuit of a Super Sandwich or some other treat. Since 2017 we have been conducting research on our favourite campus mascots, looking at how city-slicking birds such as these cope with highly variable food quality and quantity in urban environments and under increasing heat stress as Cape Town’s climate warms.
Red-winged Starlings are an excellent example of a species that has taken advantage of the opportunities offered by urban environments. While many birds avoid urban areas due to disturbance, pollution, habitat transformation and other threats that they pose, some actively exploit cities. In their natural environment, Red-winged Starlings nest on cliffs in rocky and mountainous areas, but in cities they nest on buildings. Similarly, while they would normally feed primarily on fruit and insects, they have learned that cities offer rich opportunities for scavenging on anthropogenic food.
Understanding the consequences they face as a result of replacing their natural diet with this “junk-food” is one of the aims of our research on the campus starlings. A second aim is to investigate how they cope with the lack of food on campus over weekends and holidays. Finally, we are interested in how heat stress, promoted both by the urban “heat island” effect in an already warm climate, and ongoing climate warming, interacts with urbanisation to affect the birds.
Through intensive trapping efforts during 2017, we now have a core population of >130 individually colour-ringed starlings on campus. This has allowed us to identify that the campus starling community includes both breeding residents and a large “floating” population whose presence fluctuates with time of day. “Floater” birds ringed on campus also use areas in Rondebosch and Observatory, and gather in large numbers on parts of campus in the early evenings, for reasons which currently remain mysterious. Colour-ringing has also allowed us to monitor breeding pairs and their productivity; and to assess whether the ratio of anthropogenic natural food fed to chicks matches that of the adult diet. During ringing, we collect blood samples and morphometrics from each adult. We also ringed nestlings from first broods in 2017 with a red ring with white lettering for unique ID, and blood sampled these birds too. We intend to use these samples to assess the physiological impacts of an anthropogenic diet rich in junk food during 2018. This laboratory-based component of the project is being carried out in collaboration with Lund University, Sweden, as part of a bilateral project funded by the NRF and STINT (Swedish Foundation for International Cooperation in Research and Higher Education).
Activities in 2017
- In early 2017, we began trapping and colour-ringing of adult birds within the Upper Campus population. By the end of the year, we had managed to ring 132 individuals. During the breeding season we monitored nearly 30 nests and ringed 29 nestlings.
- Through a prolonged process of habituation, we have trained several birds to jump onto a scale and “weigh themselves”, allowing us to obtain daily mass gain data. We are now working on correlating these data against climate variables and anthropogenic activity on campus.
- To date we have obtained over 1 000 mass measurements from 56 individuals and several unringed partners of these ringed birds.
- We established a Facebook page and a WhatsApp group to allow the UCT community to engage with the project and report resightings of colour-ringed birds. This has been incredibly successful, generating almost 1 700 resightings. We involved members of the UCT community in volunteer work ranging from monitoring nests to assisting with climbing for nestling ringing (with the help of the UCT Mountain and Ski Club).
- Miqkayla Stofberg’s BSc (Hons) project found dietary changes on weekends and weekdays in non-breeding birds, with a near-significant knock-on effect on mass gain but surprisingly few implications for daily time-activity budgets. Miqkayla will register for a MSc in 2018 to investigate the effect of interactions between climate warming and urbanisation on the Red-winged Starlings.
- Sarah Catto (MSc CB) completed her data collection from the 2017 breeding season. Her data suggests that the effects of fluctuations in anthropogenic food supply may be stronger in birds under the additional pressure of provisioning nestlings.
- We received funding from the NRF and STINT for a three-year joint South Africa-Sweden Research Collaboration focusing on urban avian ecology (Swedish PI: Assoc. Prof. Caroline Isaksson, Lund University). The kick-off seminar was held in Pretoria in February 2017.
- We organised a workshop on the use of biomarkers in ecophysiology with our collaborators from Lund University before the European Ornithologists Union conference held in Finland. We secured travel awards for Miqkayla and Sarah to attend this workshop.
Impact of the project
Studying a resident and high-profile population of starlings that are well-known on campus has allowed us to involve the wider university community in a citizen science project, making our research more visible and relatable. The accessibility of the project and its fieldwork has also resulted in an ideal training opportunity for younger students wanting to gain experience in behavioural research and bird observation/ handling under careful supervision. Through the help of such volunteers, the project has managed to collect a large volume of data in its first year
DST-NRF CoE grant; NRF-STINT South Africa-Sweden Research Collaboration; Claude Leon Foundation.
A/Prof. Arjun Amar (FIAO, UCT)
Dr Martin Andersson (MEEL, Lund University)
Dr Susan Cunningham (FIAO, UCT)
Dr Arne Hegemann (MEEL, Lund University)
A/Prof. Caroline Isaksson (MEEL, Lund University)
Dr Johan Nilsson (OIKOS office, Lund University)
Dr Petra Sumasgutner (FIAO, UCT)
Dr Robert Thomson (FIAO, UCT
Dr Hannah Watson (MEEL, Lund University)
Students: Ann-Kathrin Ziegler (PhD, Lund); Johan Jensen (MSc, Lund); Sarah Catto (CB MSc, UCT); Miqkayla Stofberg (BSc Hons, UCT).
Research Assistants: Dane Paijmans, Jessleena Suri.
Volunteers: Adam Begg, Laura Figenschou, Tsilavo Razafimanantsoa, UCT Mountain and Ski Club, Olivia Venter, Vince Ward, and many others.