How well do buffer circles capture the ranging behaviours of territorial raptors? Town Cape of René Brink (BRNREN007) University Supervisors: Associate Professor Arjun Amar (University of Cape Town) and Dr Megan Murgatroyd (HawkWatch International) FitzPatrick Institute of African Ornithology, University of Cape Town, Private Bag X3, Rondebosch 7701, Cape Town South Africa The copyright of this thesis vests Townin 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 Capeonly. of Published by the University of Cape Town (UCT) in terms of the non-exclusive license granted to UCT by the author. University Declaration of Plagiarism Name: René Brink Student Number: BRNREN007 Course: Conservation Biology Declaration I know that plagiarism is wrong. Plagiarism is to use another’s work and pretend that it is one’s own. I have used the ‘Conservation Biology’ convention for citation and referencing. Each contribution to, and quotation in, this essay/report/project/thesis from the work(s) of other people has been attributed, and has been cited and referenced. This essay/report/project/thesis is my own work. I have not allowed, and will not allow, anyone to copy my work with the intention of passing it off as his or her own work. ii Contents Declaration of Plagiarism .................................................................................................................................. ii Abstract .............................................................................................................................................................. 4 Introduction ....................................................................................................................................................... 5 Infrastructure and raptors ................................................................................................................................ 5 Power Lines ..................................................................................................................................................... 5 Wind Farms ..................................................................................................................................................... 6 Exclusion and Mitigation ................................................................................................................................ 6 Project Aims .................................................................................................................................................... 8 Methods .............................................................................................................................................................. 9 Data collection ................................................................................................................................................. 9 Study Species .................................................................................................................................................. 9 African Crowned Eagle (Stephanoaetus coronatus) ................................................................................... 9 Bearded Vulture (Gypaetus barbatus) ....................................................................................................... 10 Black Sparrowhawk (Accipiter melanoleucus) ......................................................................................... 10 Lappet-faced Vulture (Torgos tracheliotos) .............................................................................................. 11 Martial Eagle (Polemaetus bellicosus) ...................................................................................................... 11 Verreaux’s Eagle (Aquila verreauxii) ........................................................................................................ 11 Data Structure and Processing ....................................................................................................................... 12 Analyses of home range sizes ........................................................................................................................ 13 Home Range and Buffer Circle construction............................................................................................. 14 Evaluating the efficacy of buffer circles I - % of GPS fixes captured....................................................... 15 Evaluating the efficacy of buffer circles II - % of KDE area captured ..................................................... 15 Results ............................................................................................................................................................... 16 Data Collection and Study Species ................................................................................................................ 16 Home Range and Buffer Circle construction ................................................................................................ 16 Evaluating the efficacy of buffer circles I - % of GPS fixes captured .......................................................... 19 Evaluating the efficacy of buffer circles II - % of KDE area captured ......................................................... 21 Discussion ......................................................................................................................................................... 25 Study Limitations .......................................................................................................................................... 27 Conclusion ........................................................................................................................................................ 28 Appendix .......................................................................................................................................................... 29 Acknowledgements .......................................................................................................................................... 38 References ........................................................................................................................................................ 39 Abstract As the world’s human population increases, so does the competition for natural resources between humans and wildlife. This competition may be intense for apex predators, such as raptors, which generally require large natural areas in order to maintain their populations. Anthropogenic development within territories can cause individuals to either abandon these sites, reduce their breeding productivity, or cause direct mortality to the territory holding birds. To mitigate such impacts, one method, employed as part of Environmental Impact Assessments (EIA), is the use buffer circles centred on nest sites. Within these buffers the most damaging forms of development are prohibited. This approach assumes that raptors use the space around their nest in a uniform way, but this assumption may not always be correct and few have evaluated the effectiveness of buffer circles at protecting a species’ home range. This study uses tracking data to evaluate the effectiveness of buffer circles to cover the ranging movements of six southern African raptor species, throughout the year, as well as during their breeding and non-breeding season. My study revealed that buffer circles whose dimensions were based on the species’ 95% Kernel Density Estimate (KDE) did relatively well at capturing the proportion of individual GPS fixes, but did less well at capturing the KDE area from tracked birds. For buffer circles to capture 95% of the home range polygons (95% KDE) they would generally need to be at least twice as large as those that were derived from the 95% KDE home range area, and for some species with very large home ranges (e.g. Lappet-faced Vultures) even buffer circles that were 3 times the size failed to cover 95% of the KDE polygons. 4 Introduction The current world population stands at over 7.7 billion (World Population Review 2019) and continues to increase. Such large numbers of people require more resources to support and sustain them – which includes transforming large tracts of natural land into settlements, agriculture, resource harvesting, or for energy development. Unfortunately, such land use changes can result in degradation and disruption of the natural ecosystems on which many species depend on. While some species have the potential to adapt to degraded habitats, and may even thrive in an urbanised or agricultural landscape (Malan & Robinson 1999; Suri et al. 2017; Kettel et al. 2018), others are unable to adapt as well and can abandon their territories (Blair 1996; McKinney 2002; Fischer et al. 2015; Krüger et al. 2015). Some developments, such as energy infrastructure may be so damaging that they can lead to direct mortality and decline of local populations (Carrete et al. 2009; Dahl et al. 2013). Infrastructure and raptors Energy infrastructure can have a negative effect on many avian species at risk. Raptors are affected both directly (increased risk of mortality due to collisions or electrocution) and indirectly (increased avoidance behaviour, habitat loss, habitat fragmentation, and species displacement) (Dwyer et al. 2018). In most cases, raptor populations are more greatly