Urban environments create novel challenges and opportunities for birds. Understanding why and how some birds are able to adapt to urban landscapes, and others are not, is important to predict how ongoing urbanisation is likely to impact birds. This project aims to understand how birds in human-altered landscapes cope with the opportunities and pressures of human life.

The Red-winged Starling project
Red-winged Starlings Onychognathus morio have developed a reputation amongst the UCT community for being sly, lunch-thieving pests – but they are apparently also remarkably successful in highly urban environments. Since 2017 we have studied how these birds cope with highly variable food quality and quantity in urban environments, the stresses of sharing their space with large numbers of people, and of high summer temperatures as Cape Town’s climate warms. Early correlative work showed that adult starlings benefit from high availability of anthropogenic food, gaining more weight on weekdays than on weekends, but that chicks seem to suffer, with those experiencing many high human presence days while in the nest showing reduced growth compared to those raised during lower human presence days (i.e. those whose nestling period overlaps with public holidays and vacations). We also found that more built-up areas on campus were occupied by larger birds, suggesting that starlings perceive these areas to be higher quality. Indeed, faecal glucocorticoid metabolite concentrations in starling droppings are negatively correlated with human foot traffic levels outside of the breeding season; suggesting that starlings suffer reduced stress in the presence of high human numbers, perhaps because of the ready availability of anthropogenic food or because humans deter natural starling predators.

However, even though adults benefit from high human presence on campus, nestlings appear to be negatively affected, and experimental work (e.g. by Miqkayla Stofberg over the last several years) has not clarified whether food quality or other correlated urban stressors are to blame. In 2023, MSc student Abiodun Ademola continued her work testing the hypothesis that negative impacts of high human presence on nestling growth may be mediated by stress effects associated with adult nest defence behaviours (breeding adults frequently divebomb passers-by when nests contain nestlings). Abiodun also continued data collection on behaviour and stress levels of adult starlings both inside and outside of the breeding season.

The starlings again played an important role in undergraduate and postgraduate teaching in 2023. Susie Cunningham led a third-year project on the BIO3013F Global Change Ecology course looking at starling responses to hot weather on campus. This project teaches 3rd-year students how to collect and analyse behaviour data from free-living animals. This was the 8th year this project has run (2015–23, with a 1-year Covid-19-related hiatus) and it is becoming apparent that starlings adjust the onset of heat-dissipation behaviours annually in relation to the prevailing weather conditions that year, suggesting a great deal of behavioural plasticity in heat-load management. Dr Celiwe Ngcamphalala used our annual starling ‘catch week’ in mid-winter to expose Biological Sciences Honours students to methods used to study avian stress physiology, inviting the students to take part in catching efforts and observe and record data on blood-sampling, measurement and ringing, to aid their understanding of invasive versus non-invasive methods of studying wild animals.

Anthropogenic food as a resource for urban birds
In addition to her work on the starlings, Miqkayla Stofberg’s PhD research attempted to better understand the importance of anthropogenic food in allowing bird species to adapt to living in urban environments. Miqkayla undertook a review of the literature and extracted the proportion of urban birds’ diet that is made up of anthropogenic food. She then explored which traits are most closely associated with the propensity to consume these types of food.

Interactions between urbanisation and climate change
Rapid urbanisation is a major feature of anthropogenic global change in the current century. Another is rapid and ongoing climate change. These two global change drivers do not act in isolation and impacts of climate change on wildlife could be exacerbated, or buffered, in urban areas. This is because major changes in habitat structure, food and water availability, disease exposure and species interactions and pollution (light, sound and chemical) may all affect how wildlife can respond to rising temperatures and changing weather patterns. Additionally, urban environments tend to be hotter than surrounding natural landscapes (the ‘urban heat island effect’), except in arid areas where they may be cooler. The UCT starling team and collaborators in Sweden co-authored a major perspectives paper in the journal Global Change Biology highlighting how we might expect the forces of urbanisation and climate change to interact in their effects on wildlife. This paper has already attracted numerous citations and we hope it will inspire further research in this area.

Activities in 2022

  • Abiodun Ademola continued her MSc project which focuses on understanding the effect of fluctuations in human foot traffic on stress levels in adult and nestling Red-winged Starlings, using faecal glucocorticoid metabolites as a proxy for stress. She is also investigating the downstream impacts on fitness by measuring body mass changes and reproductive success. Abiodun is supervised by Susie Cunningham and Celiwe Ngcamphalala.
  • A highly successful trapping effort in mid-2023 saw 35 new colour-ringed starlings added to the study population, bringing the total number of adults starlings ringed during the course of the project to 312. An additional 55 nestlings were ringed in the nest in 2023.
  • Body mass maintenance and breeding monitoring continued throughout 2023: these data will be used to investigate the effects of societal recovery from the COVID-19 pandemic on the productivity of urban wildlife, and, in the long term, to assess how climate change and urbanisation together impact fitness of urban wildlife.

HIghlights

  • Miqkayla Stofberg graduated with her PhD entitled ‘The influence of anthropogenic food on bird behaviour and community structure in urban environments’ and presented one of her chapters at the BirdLife South Africa LAB meeting in Wilderness.
  • The team published a paper on the impacts of urban-climate change interactions on wildlife in a leading journal Global Change Biology.

Impact of the project
Studying the starlings on campus has allowed us to involve the wider university community in a citizen science project, making our research more visible and relevant. 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. In addition, the starling project supports teaching at undergraduate (third year) and post-graduate (honours) levels, exposing students to the skills needed for field ornithology.

Key co-supporters
DSI-NRF CoE grant; NRF-STINT South Africa-Sweden Research Collaboration; NRF ACCESS grant, Vice-Chancellors’ Future Leaders programme.

Research team 2023
A/Prof. Arjun Amar (FIAO, UCT)
A/Prof. Res Altwegg (SEEC, UCT)
Dr Pippin Anderson (EGS, UCT)
Dr Martin Andersson (MEEL, Lund University)
A/Prof Susan Cunningham (FIAO, UCT) Dr Celiwe Ngamphalala (BioSci, UCT)
Dr Arne Hegemann (MEEL, Lund University)
Dr Sally Hofmeyr (FIAO, UCT)
A/Prof. Caroline Isaksson (MEEL, Lund University)
Dr Johan Nilsson (OIKOS office, Lund University)
Dr Petra Sumasgutner (KLF, University of Vienna)
A/Prof. Robert Thomson (FIAO, UCT)
Dr Hannah Watson (MEEL, Lund University)

Students:  Miqkayla Stofberg (PhD, UCT); Jessleena Suri (PhD, UCT); Abiodun Ademola (MSc, UCT).

Volunteers: Babette Fourie, Daniella Mhangwana, Joel Radue, Mila Truter, Sam Wagstaff, Kyle Walker and many others.