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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 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 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 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 affectedby 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 2018

  • In 2018, we ringed 46 Black Sparrowhawk chicks from 42 active territories and installed 12 nest cameras to collect data on prey provisioning rates.
  • Andrew Jenkins conducted his 30th field season monitoring and colour ringing Peregrine Falcons on the Cape Peninsula.
  • Rebecca Muller undertook her Conservation Biology MSc project in collaboration with the University of Kwa-Zulu Natal, unravelling urban productivity of Crowned Eagles. The collaborative research team included Dr Shane McPherson and Prof. Colleen Downs.
  • We presented our research at the 4th Learn About Birds (LAB) conference in Langebaan, Western Cape, at the 27th International Ornithological Congress (IOC) in Vancouver, Canada, and at the Annual Meeting of the Raptor Research Foundation (RRF) in Skukuza, RSA.
  • Together with Assoc. Prof. Caroline Isaksson, we continued the three-year joint South Africa-Sweden Research Collaboration focusing on urban avian ecology, funded by the NRF and STINT. The mid-term workshop was held in De Hoop Nature Reserve in October 2018 where we worked on a review paper within the joint research team and advised joint students on their research projects.

Highlights:

  • We organised a symposium at the International Ornithological Congress (IOC) in Vancouver, Canada (Topic: “Human-raptor interactions: From conservation priorities to conflict mitigation”) with Prof. Steve Redpath and Petra Sumasgutner as key-note speakers.
  • Sanjo Rose published her 2015 BSc Honours thesis “Exploring the influence of urbanization on morph distribution and morph-specific breeding performance in apolymorphic African raptor” in Journal of Raptor Research.

Impact of the project

Our 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 supporters

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

Research team

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)

Research Assistant: Dr Shane MacPherson.