UNIVERSITY of CAPE TOWN in Fulfilment of the Requirements for the Degree of Doctor of Philosophy

Ecology of the Verreaux’s eagle Aquila verreauxii in natural and agriculturally transformed habitats in South Africa Sarah Megan Murgatroyd MRGSAR004 February 2016 SUBMITTED TO THE UNIVERSITY OF CAPE TOWN In fulfilment of the requirements for the degree of Doctor of Philosophy UniversityAnimal Demographyof Cape Unit Town & Percy FitzPatrick Institute of African Ornithology Department of Biological Sciences, Faculty of Science University of Cape Town Supervised by: Prof. Les Underhill and Dr. Arjun Amar The copyright of this thesis vests in the author. No quotation from it or information derived from it is to be published without full acknowledgement of the source. The thesis is to be used for private study or non- commercial research purposes only. Published by the University of Cape Town (UCT) in terms of the non-exclusive license granted to UCT by the author. University of Cape Town Contents Thesis abstract ............................................................................................................ 1 Acknowledgements ..................................................................................................... 4 Chapter 1. Introduction ............................................................................................... 8 Chapter 2. The influence of agricultural transformation on the breeding performance of a top predator: Verreaux’s eagles in contrasting land use areas ............................ 34 Chapter 3. Adaptability of a specialist predator: The effects of land use on diet diversification and breeding performance of Verreaux’s eagles ................................ 66 Chapter 4. Ranging behaviour and foraging patterns of Verreaux’s eagles in areas of contrasting land use .................................................................................................... 98 Chapter 5. Predicting soaring flight behaviours of Verreaux’s eagles and lift availability in contrasting landscapes ....................................................................... 134 Chapter 6. Synthesis and conclusions ..................................................................... 173 Thesis abstract Agricultural transformation generally has a negative impact on biodiversity. Owing to landscape fragmentation and reduced prey availability, predators that inhabit transformed areas are usually forced to increase hunting effort or diversify their diet and this can have negative consequences for fitness or demographic parameters. Agricultural landscapes are therefore rarely considered important in the conservation of top predators. The Verreaux’s eagle Aquila verreauxii has experienced loss of natural habitat due to agricultural transformation through much of its range. Despite the conspicuous nature and widespread distribution of Verreaux’s eagles in sub- Saharan Africa, there is a paucity of information on the mechanism behind the recently observed population declines of this species, which have resulted in the recent re-classification as “Vulnerable” (from “Least Concern”) in South Africa. This thesis aims to explore how land transformation influences changes in several key ecological components and demographic parameters, namely breeding performance, diet and movement ecology. In this thesis, I study two geographically adjacent populations of Verreaux’s eagles; one located in a natural area (Cederberg) and one in an agriculturally transformed area (Sandveld), in the Western Cape Province, South Africa, from 2011–2014. I investigate the breeding performance of the two populations. In contrast to what was anticipated I found that breeding productivity was 2.7 times greater in the agricultural than in the natural area. Population modelling suggested that in isolation the Cederberg population is unlikely to be self-sustaining, whereas the eagles breeding in the Sandveld region are likely to be acting as a source population. However, I did not have any information about juvenile or adult survival in either area. Contrasting survival rates could distort these results and are in need of further research. Verreaux’s eagles are generally regarded as dietary specialists. I therefore investigated the diet composition of eagles in the two study areas as a proxy to better understand prey availability and to look for evidence of behavioural flexibility to different availability of prey resources. The relationship between diet breadth and 1 breeding performance was explored locally and regionally using data from previous studies. Eagles in the Sandveld were found to have a more diverse diet than eagles in the Cederberg, which rely on their traditional prey, rock hyrax Procavia capensis. Theory on specialist predators assumes that diet diversification will cause reduced breeding performance. In particular, individuals within a species with more diverse diets due to reduced availability of primary prey species can display reduced breeding performance. In direct contrast to this, eagles with broad diet did not exhibit trends for reduced breeding performance, both locally and across southern Africa. The movements of five adult Verreaux’s eagles were investigated using high- resolution GPS trackers. Thereby providing detailed information on ranging behaviour of this species, including home range estimates and spatiotemporal parameters of trips away from the nest site. Although no differences between the two study areas were found in trip parameters/effort, there was some evidence for a difference in the timing of peak activity, which may have been caused by topographical differences driving contrasting lift availability between the study areas. Additionally, a habitat selection analysis within the Sandveld suggested a preference for partially transformed areas, which is likely to be related to prey availability. Lastly, data from the high-resolution GPS tags were used to identify different flight behaviours and evaluate the availability of lift in the topographically contrasting study areas. This chapter identified topographical and meteorological correlates of orographic and thermal soaring so that the spatial distribution of lift driving soaring flights could be predicted across the study areas. This research indicated the relatively flat Sandveld region might actually be a more favourable energy landscape by providing an environment with greater predicted lift availability compared to the Cederberg Mountains. Following the findings of this study, I conclude that agricultural land use areas can actually contribute positively to the conservation of Verreaux’s eagle. Although this species is typically thought of as a mountain specialist, the findings here demonstrate that the agricultural Sandveld region can sustain a productive population, provided that there is some suitable breeding habitat (i.e. rocky outcrops with cliffs). The 2 productivity of this population is contributed to by the provision of a diverse prey base, an environment conducive to good nesting success and a landscape favourable for low-energy flying. The current level of agricultural transformation in the Sandveld does not appear to cause fitness constraints. However, further expansion or intensification of the agricultural footprint is likely to incur negative effects and it will also be important to maintain heterogeneous habitat. Further research should be aimed at assessing the ecology and life history traits of Verreaux’s eagle in other agricultural environments that have transformed more than the Sandveld. This would help to find the ecological threshold for transformation that I predict from the findings of this thesis. Beyond a threshold point, further agricultural transformation will probably be detrimental to Verreaux’s eagle and other biodiversity. These results highlight the potential conservation value of some agricultural areas and the need for effort to be made to integrate agriculture and conservation worldwide. 3 Acknowledgements It’s difficult to sum up in words how lucky I feel and how grateful I am for the time I have spent undertaking this research. The Cederberg and the Sandveld both have special places in my heart, largely due to the incredible people I have crossed paths with. Dawie and Lizette Burger, without you and your endless enthusiasm, I am convinced this work would not have been possible. Thank you for making Cederberg home for me, for many morale boosters during the cold rainy winters, for literally and figuratively scraping me off the floor in times of need, for your eagerness to always help, for my little friend Karli and most importantly for your friendship. These thanks are extended to Hennie and Rene Spamer and Charl du Toit who generously shared Driehoek with me and were always there to help me out. Thanks also to George van der Watt, who gave me a place to call home in the Cederberg during my first year there. It was such a privilege to live on that little piece of paradise and it gave me an invaluable foothold into my study area. Living and working in the Cederberg also meant that I frequently relied on the generosity and help from members of CapeNature and the Cederberg Conservancy. Particular thanks go to all of the landowners, Patrick Lane, Rika du Plessis, Colin Veloen, Willem Titus and all of the other rangers. In the Sandveld I had many homes and I am grateful to all of the people who provided them: Tom Vanderhaeghen and Tessy Plettinck, Patrick and Karin Carter, Nick Taylor and Felicity Strange, Louise and Gary Mann, Tillia Kotze and family and Garry Sheard. Your friendships have been an exceptional

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