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Understanding urban raptor populations

Urban development is increasing across the globe and poses a major threat to biodiversity, which is often relatively low in human-modified landscapes. In fact, next to climate change, the United Nations considers urbanisation to be the biggest environmental challenge to the maintenance of biodiversity. Globally, there are now more people living in urban than in rural areas, 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 southern 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 Sparrow-hawks Accipiter melanoleucus have been monitored over for 30 and 20 years, respectively. During this time, the populations of both species within the study area have increased markedly. Both species profit from the abundance of suitable nesting sites and their favoured avian prey, such as pigeons, doves and Common Starlings Sturnus vulgaris. 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, senescence 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, sound 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 urban environments. We use the Black Sparrowhawk study system and a biomarker approach to investigate such possible health impacts. 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

Activities in 2019

  • In 2019 we ringed 34 Black Sparrowhawk chicks from 18 territories.
  • Post-doc Petra Sumasgutner and PhD student Carina Nebel presented our research at the European Ornithological Union (EOU) Conference in Cluj, Romania.
  • Together with Assoc. Prof. Caroline Isaksson from Lund University, Sweden, we continued the three-year joint NRF/STINT South Africa-Sweden research collaboration focusing on urban avian ecology. We commenced writing a review paper focusing on urban avian ecology.
  • Dr Chima Nwaogu started a post-doctoral fellowship with the group. Part of his research is focused on understanding whether the immune system of Black Sparrowhawk chicks varies along the urbanisation gradient.
  • In 2019 our research extended into another urban-raptor system. Rebecca Muller received a distinction for her Conservation Biology MSc thesis, undertaken in collaboration with Dr Shane McPherson and Prof. Colleen Downs (UKZN). Rebecca unravelled the productivity of urban Crowned Eagles Stephanoaetus coronatus. A paper from this thesis is currently in review with the journal Condor.
  • We submitted a paper to PLoS One on the influences of weather and urbanisation on Peregrine Falcon breeding success and phenology. The paper used Dr Andrew Jenkins’ long-term dataset on breeding peregrines in Cape Town.
  • BSc Hons student Kyle Walker analysed prey remains from Peregrine Falcon nests that have been collected over multiple years as part of Dr Jenkins’ monitoring project. Kyle’s dissertation explored how diet differs across the urban gradient and whether diet has changed from 20 years ago when Dr Jenkins first examined diet in this population.

Highlights

  • Assoc. Prof Arjun Amar and Dr Juan Diego Ibáñez-Álamo co-organised a symposium at the EOU in Cluj, Romania, on “Urban ornithology: threats and opportunities” with Profs Dan Chamberlain and Peter Batary as key-note speakers.
  • Arjun Amar, Chevonne Reynolds Dan Chamberlain and others published a paper on the Luxury Effect for South African bird richness in Global Change Biology.
  • Petra Sumasgutner, Arjun Amar and volunteer Ann Koeslag published a paper in the Journal of Avian Biology entitled “Senescence in the city: exploring ageing patterns of a long‐lived raptor across an urban gradient. The journal chose a photo of Black Sparrowhawks for their cover of that issue.

Impact of the project

The project is 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

Key co-supporters
DST-NRF CoE grant; NRF-STINT South Africa-Sweden Research Collaboration, Claude Leon Foundation.

Research team 2019
A/Prof. Arjun Amar (FIAO, UCT)
Dr Petra Sumasgutner (FIAO, UCT)
Dr Chima Nwaogu (FIAO, UCT)
Prof. Res Altwegg (SEEC, UCT)
Dr Andrew Jenkins (ADU, UCT)
Prof. Dan Chamberlain (U. Turin)
Dr Chevonne Reynolds (Wits)
Dr Arne Hegemann (MEEL, Lund University)
A/Prof. Caroline Isaksson (MEEL, Lund University)
Dr Hannah Watson (MEEL, Lund University)
Prof. Colleen Downs (UKZN)
Dr Shane McPherson (UKZN)

Students: Carina Nebel (PhD, UCT); Rebecca Muller (CB MSc, UCT); Kyle Walker (BSc Hons, UCT).

Research Assistants: Dr Shane McPherson, Burghen Siebert.

Volunteers: Ann Koeslag, Margaret MacIver, Antje and Bernard Madden.