Understanding urban raptor populations
Urban development is increasing across the globe and poses a major threat to biodiversity, which is often relatively depauperate in human-modified landscapes. In fact, next to climate change, the United Nations consider urbanisation the biggest environmental challenge to maintain biodiversity of our time. More people live in urban than in rural areas globally, and the trend towards urbanisation is faster in Africa and Asia than in any other regions of the world.
The Cape Peninsula is located on the south-western tip of the African continent, where climate change is predicted to be particularly rapid and severe. In this project we focus on the responses of raptors to increasing urbanisation under climate change. On the Cape Peninsula, urban breeding Peregrine Falcons Falco peregrinus and Black Sparrowhawks Accipiter melanoleucus have been monitored over 30 and 18 years, respectively. During this time, the populations of both species within the study area have increased markedly. We use these two long-term data sets on individually marked birds to investigate the effects of urban-living and weather on breeding phenology, reproductive performance, survival and population trends.
Beside habitat loss and fragmentation, wildlife in urban areas might also be negatively affected by altered bio-geochemical cycles and the introduction of novel urban stressors such as light, noise and chemical pollutants. Urban-exploiting or adaptable species that are able to make use of abundant resources in the short-term, might thus still suffer from other hidden costs of urban living which could undermine their long-term health and persistence in an urban environment. We use the Black Sparrowhawk study system and a biomarker approach to investigate such possible health impacts. The species seemingly thrives in the city, taking advantage of the availability of nesting trees in alien Eucalyptus and pine plantations and the high prey abundance of pigeons and doves. Taking small blood samples from adults and their offspring, we have quantified eco-physiological parameters such as immune assays, oxidative stress and dietary antioxidants. The eco-physiological component of this research has been carried out in collaboration with Lund University, Sweden, as part of a bilateral project funded by the NRF and STINT which will run between 2017-2020.
Activities in 2017:
- In 2017, 66 Black Sparrowhawk chicks fledged from 36 territories. This is the largest number of fledglings since the beginning of the project in 2000.
- Sanjo Rose completed her BSc Honours project investigating breeding phenology, performance and colour morph distribution along an urban-rural gradient. Her thesis resulted in papers published in a special issue on “Behavioural and Ecological Consequences of Urban Life in Birds“ in Frontiers in Ecology and Evolution, and another in the Journal of Raptor Research.
- Jessleena Suri published a paper from her Conservation Biology Master’s thesis in Ibis on how urban prey abundance might buffer Black Sparrowhawks from potential negative health impacts of urbanisation. ulia van Velden published a paper from her 2013 Honours project on the impact of skin burrowing mites on Black Sparrowhawk breeding performance in Auk.
- PhD student Carina Nebel visited Lund University in November to conduct the laboratory work necessary for the biomarker approach.
- We presented our research at the European Ornithologists’ Union (EOU) conference in Turku, Finland, where we had the largest representation of South Africans to date at a European ornithological conference (funded through the NRF-STINT grant), and at the annual conference of the Birds of Prey Programme of the Endangered Wildlife Trust (EWT) at Witsand, Northern Cape.
- Together with Assoc. Prof. Caroline Isaksson, we received funding for a three-year joint South Africa-Sweden Research Collaboration focusing on urban avian ecology from the NRF and STINT.
- The kick-off seminar was held in Pretoria in February 2017 and a workshop on the use of biomarkers in ecophysiology was held before the EOU conference in Finland. Three PhD candidates from the raptor group attended who will apply the biomarker approach in their research, Carina Nebel and Edmund Rodseth from the Black Sparrowhawk project, and Christiaan Brink from the Vulture Conservation Project.
Impact of the project
Our project represents one of the first to examine individual health and productivity of a bird species in relation to urbanisation in Africa. Our results have considerable implications for potential changes in phenology or productivity for the regions’ avifauna as African urbanisation continues.
DST-NRF CoE grant; NRF-STINT South Africa-Sweden Research Collaboration, Claude Leon Foundation.
Dr Arjun Amar (FIAO, UCT)
Dr Petra Sumasgutner (FIAO, UCT)
Dr Res Altwegg (SEEC, UCT)
Dr Andrew Jenkins (ADU, UCT)
Volunteers: Ann Koeslag, Margaret MacIver, Antje Madden, Bernard Madden.
Students: Carina Nebel (PhD, UCT); Jessleena Suri (CB MSc, UCT), Sanjo Rose (BSc Hons, UCT).
Research Assistant: Dr Shane MacPherson.