Global change and urban birds

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 for predicting 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 urban life. In 2025, we worked across three urban study systems: the Red-winged Starlings on UCT’s Upper Campus, Crowned Eagles in Durban, and Spotted Thick-knees in Cape Town.

Red-winged Starlings and how urban birds cope with human pressures 
Since 2017 we have studied how Red-winged Starlings Onychognathus morio on UCT’s urbanised Upper Campus cope with the highly variable food quality and quantity associated with human-dominated environments and 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 more high-human-presence days while in the nest showing reduced growth compared to those experiencing fewer (i.e. those whose nestling period overlaps with public holidays and vacations). In 2025, we published a paper led by former honours student Kagiso Nhlapo, which showed that faecal glucocorticoid metabolite concentrations in starling droppings are negatively correlated with human foot traffic levels outside of the breeding season, suggesting that starlings experience less 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, these data were collected during 2021, when the campus human community was still recovering from the Covid-19 pandemic and foot traffic on campus was lower than normal during weekdays.

In 2025, MSc student Abiodun Ademola finalised her lab work on how adult starlings respond to human presence in terms of stress hormone expression while breeding versus not breeding, and how nestlings’ stress hormone expression and growth is linked to human foot traffic and noise. Surprisingly, Abiodun found an opposite effect to the one found by Kagiso: her data suggest that adult starlings’ glucocorticoid levels rise alongside increasing human presence during the nonbreeding season. There were many more people on campus during Abiodun’s study, however, as Covid-19 was a distant memory by the time she collected her samples. We hypothesise that perhaps intermediate levels of foot traffic are best for adult starlings: too few of us around and they feel hungry (no slap chips!) and scared (because there are no humans to frighten away the Peregrine Falcons Falco peregrinus and Black Sparrowhawks Accipiter melanoleucus), but too many of us and our noise and hustle becomes stressful again. However, everything changes when the birds are breeding: stress hormones are suppressed overall, and even more so on weekdays, when all our food discards might make life easier for parents trying to feed both themselves and their hungry chicks. For nestlings, human presence and noise is always a challenge: Abiodun’s data confirmed that nestling growth is suppressed when foot traffic is high, and furthermore that nestling stress hormones rise when there are a lot of us about.

The starlings also played an important role in undergraduate and postgraduate teaching in 2025. A/Prof. 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 third-year students how to collect and analyse behaviour data from free-living animals. This was the tenth year this project has run (2015–25, with a one-year COVID-19-related hiatus) and the growing dataset now allows students to also explore the challenges and possibilities of analysing long-term data. Dr Celiwe Ngcamphalala again used our annual starling trapping 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 the catching effort 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.
 

Interactions between urbanisation and climate change
Climate change and urbanisation are two of the most pervasive current drivers of global change. 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, 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. In 2025, MSc student Leslie Bayanza continued her work using the Red-winged Starlings to improve our understanding of how human pressures may interact with rising temperatures to affect behaviour and fitness, building on earlier pre-pandemic work by Dr Miqkayla Stofberg on this topic. Leslie collected data on adult behaviour and body mass, and on nestling growth in relation to air and nest temperatures and foot traffic. Preliminary data analyses suggest body mass declines during hot weather may be buffered by human presence (perhaps due to easy availability of high-calorie food), but this could depend on breeding status. Leslie’s final field season was the starlings’ 2025/26 breeding season. At the time of writing, she is busy analysing her own data and the long-term dataset: watch this space!

Alongside the starlings, another African urban ‘success story’ is the Crowned Eagle Stephanoaetus coronatus, which has reached higher densities in the Durban metropolitan area than anywhere else documented within its range. In 2025, an international team of collaborators including researchers from UKZN and the University of Vienna installed microclimate monitoring equipment at several Crowned Eagle nests across the city, in collaboration with the Fitz’s Hot Birds Research Project team. The project investigates how Crowned Eagles respond to heat stress, extreme weather events, and urban heat-island effects that may influence nest-site selection and breeding success. The sensors measured temperature, humidity, and solar exposure, alongside a motion-triggered camera programmed to record nest activity at five-minute intervals. These data will help quantify how adults and chicks regulate heat through behaviours such as shading, repositioning, and nest attendance, providing valuable insights into how climate change and urbanisation may shape raptor breeding ecology in South Africa.

Spotted Thick-knees in Cape Town and artificial light at night
Within urban environments across the globe, the proliferation of artificial light at night (ALAN) has intensified. However, the impacts of this form of pollution on birds are not well understood. The effects may be particularly profound for nocturnal species, with impacts being either potentially beneficial or detrimental. For example, ALAN can attract insects and could thereby improve foraging conditions for nocturnal insectivores, but it might also interfere with their sensory systems for detecting and capturing prey, or it may increase their risk of predation. We have been exploring this question with the Spotted Thick-knee Burhinus capensis. We aim to understand how ALAN influences habitat selection in this nocturnal insectivorous species which breeds in urban areas in South Africa. In 2025, postdoctoral fellow Dr Olufemi Olubodun attached GPS tracking devices to 11 Spotted Thick-knees in urban areas around Cape Town. The project involved trapping and tagging Thick-knees and following their breeding performance. The data will provide insight into how the birds alter their movement and foraging patterns under the influence of ALAN as well as during breeding. This is the first time that this species has ever been tracked.

Activities in 2025

• Abiodun Ademola completed her MSc write-up on the adrenocortical responses of Red-winged Starlings to high human pressure in an urban environment, for submission in early 2026. Abiodun is supervised by Susie Cunningham and Celiwe Ngcamphalala.
• Leslie Bayanza completed data collection for her project on the interaction between weather and human presence on starling body mass maintenance and breeding success. Leslie is both using the long-term datasets amassed by the project since 2017 and collecting novel data of her own. Leslie is supervised by Susie Cunningham and Celiwe Ngcamphalala.
• A highly successful trapping effort in mid-2025 saw 45 new colour-ringed starlings added to the study population, bringing the total number of adult starlings ringed during the project to 377. An additional 55 nestlings were ringed in 2025.
• Body mass maintenance and breeding monitoring of the starlings continued throughout 2025: 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 the fitness of urban wildlife.
• An intense Crowned Eagle season resulted in seven more adults and five juveniles equipped with high-resolution GPS trackers, 18 chicks ringed, and 11 nest cameras and six microclimate surveillance sets installed.
• Eleven adult Spotted Thick-knees were GPS-tagged between October and December. The breeding events in six breeding territories were also monitored.
• A/Prof. Robert Thomson conducted urban bird point counts around Cape Town for two global collaborative projects investigating avian diversity in urban areas. The first explores the role of university campuses as bird hotspots in cities; this project includes approximately 70 cities and their university campuses worldwide. The second explores the structural land-sharing versus the land-sparing model of urban development and how these affect avian diversity; this project includes about 50 cities globally.
   

Highlights

• Kagiso Nhlapo’s honours paper ‘High human presence is correlated with lower faecal glucocorticoid metabolite levels in an urban bird population’ was published in the journal Hormones and Behaviour.
• Pilot data on nest microclimates for urban Crowned Eagles were collected for the first time.
• Initial data collection on the movement and breeding biology of urban Spotted Thick-knees is ongoing.
• Arjun Amar co-authored a paper that explores the patterns of the luxury effect in relation to levels of inequality in urban regions in People and Nature.
• Lara Howard graduated with her Conservation Biology MSc degree on the movement ecology and energy expenditure of urban Crowned Eagles.
   

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 postgraduate (honours) levels, exposing students to the skills needed for field ornithology. The Crowned Eagle heat-island project demonstrates how locally grounded research can generate scientific, educational, and societal impact. By investigating how large raptors cope with extreme heat and weather events, the project contributes valuable knowledge to conservation planning in increasingly urbanised landscapes. Together, these initiatives strengthen the Fitz’s role as a leader in applied urban and climate-responsive ornithology. In addition, the ALAN project shows how urban light impacts bird movement, improving knowledge of nocturnal behaviour in ALAN-polluted landscapes. This will advance understanding of the implications of increasing urbanisation on birds and inform conservation management plans.

Key co-supporters
UCT Vice-Chancellors’ Future Leaders programme; Mandela Rhodes Scholarship programme; Mastercard scholarship programme; BOU Brenda and Tony Gibbs Award.

Research team 2025
Team leaders and collaborators:
A/Prof. Arjun Amar (FIAO, UCT)
A/Prof. Res Altwegg (SEEC, UCT)
A/Prof. Susan Cunningham (FIAO, UCT)
Dr Celiwe Ngcamphalala (BioSci, UCT)
Dr Sally Hofmeyr (FIAO, UCT)
A/Prof. Petra Sumasgutner (KLF, U. Vienna)
Dr Shane Sumasgutner (KLF, U. Vienna / UKZN)
Prof. Colleen Downs (UKZN)
A/Prof. Robert Thomson (FIAO, UCT)
Varalika Jain (KLF, U. Vienna)
Dr Ralph Buij (Wageningen U. / Peregrine Fund)
Dr Juan Diego Ibáñez Álamo (U. Granada) 
Dr Olufemi Olubodun (FIAO, UCT)
 

Students:
 Jessleena Suri (PhD, UCT Stats); Abiodun Ademola (MSc, UCT); Leslie Bayanza (MSc, UCT); Lara Howard (CB MSc, UCT); Lucas Landolfi (MSc, KLF)

Volunteers:
Mila Truter, Joel Radue, Daniella Mhangwana, Josua Wenzel, Suzanne Hofmeyr, Ilana Engelbrecht, Ben Wittenberg, Anthony Boetcher, Edith Binnema, Johannes Ploderer, Sarah Guttenberger, Martiné van den Berg, and many others.