Street-wise : does prey abundance buffer black sparrowhawks (Accipiter melanoleucus) from the negative health impacts of urbanisation?

Master Thesis


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University of Cape Town

As trends in urbanisation continue globally, there is a growing need to understand the impacts of urban development on wildlife. Whilst urban impacts on patterns of diversity and abundance of species have been well-studied, there remains a distinct lack of understanding around the impacts on ecological interactions. Different species have different levels of tolerance to urban disturbance, some species even appear to thrive in urban areas and make use of human-subsidised resources; but the physiological costs and trade-offs faced by urban-dwelling species are poorly understood. Given that their range in South Africa has only recently expanded into the human-dominated landscapes of the Western Cape, the Black Sparrowhawk (Accipiter melanoleucus) provides an excellent opportunity to explore some of these questions. In this study we explored how urbanisation may affect the health of this raptor on the Cape Peninsula, South Africa. If the health of this species is negatively influenced by levels of urbanisation, this might be driven by differences in diet and prey availability across the urban spectrum. Thus, we explored this potential mechanism by examining diet composition and assessing prey abundance within different territories and habitat types. The health of nestling Black Sparrowhawks was evaluated through their immune response (Heterophil/Lymphocyte ratio in white blood cell counts), body condition (based on morphometric measurements) and blood parasite infection (presence and abundance of Haemoproteus and Leucocytozoon). Trends in diet composition along a gradient of urban cover were determined through the analysis of prey remains collected in the immediate nest surroundings and differences in prey abundance were determined through point counts in different habitat types.