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Amywhitehead-Phdthesis.Pdf (12.87Mb) Tools for managing threatened species: improving the effectiveness of whio conservation A thesis submitted for the Degree of Doctor of Philosophy in Ecology at the University of Canterbury by Amy Whitehead University of Canterbury Christchurch, New Zealand 2009 In loving memory of Geoffery Field Sommerville 1917 - 2007 Table of contents Abstract ............................................................................................................................ 3 Preface .............................................................................................................................. 8 1. Predation vs. habitat modification: quantifying the drivers of global change Abstract .................................................................................................................. 15 Introduction ........................................................................................................... 15 Methods ................................................................................................................. 18 Results ................................................................................................................... 22 Discussion.............................................................................................................. 25 Acknowledgements ............................................................................................... 27 2. Large-scale predator control improves the productivity of a rare New Zealand riverine duck Abstract ................................................................................................................. 31 Introduction ........................................................................................................... 32 Methods ................................................................................................................. 35 Results ................................................................................................................... 39 Discussion.............................................................................................................. 46 Acknowledgements ............................................................................................... 51 3. Large-scale predator control increases population viability of a rare New Zealand riverine duck Abstract ................................................................................................................. 55 Introduction ........................................................................................................... 56 Methods ................................................................................................................. 58 Results ................................................................................................................... 63 1 Discussion.............................................................................................................. 68 Acknowledgements ............................................................................................... 72 4. More ducks for your bucks: a multi-scale assessment of habitat quality-fitness relationships to enhance management of a threatened riverine duck Abstract .................................................................................................................. 77 Introduction ........................................................................................................... 78 Methods ................................................................................................................. 81 Results ................................................................................................................... 87 Discussion.............................................................................................................. 92 Acknowledgements ............................................................................................... 97 5. Tools for managing threatened species: improving the effectiveness of whio conservation Identifying historical and contemporary threats .................................................. 102 Assessing the effectiveness of management ........................................................ 107 Identifying areas of high quality habitat .............................................................. 109 Implications for whio conservation ..................................................................... 112 General implications for conservation ................................................................. 115 6. Appendices References ........................................................................................................... 121 Acknowledgements ............................................................................................. 139 Curriculum Vitae ................................................................................................. 144 MacDiarmid Young Scientist of the Year ............................................................ 146 2 Abstract Conservation frequently requires immediate responses to prevent further declines of im- perilled populations, often in the absence of detailed information. Consequently, popu- lation distribution patterns are often used to guide conservation decisions. However, distribution patterns may be misleading if threats have restricted species to low quality habitat. This issue means it is not always apparent where management efforts should be concentrated for maximum conservation gain. My aim was to improve the effectiveness of threatened species conservation by investigating this issue in whio (blue duck - Hy- menolaimus malacorhynchos), a New Zealand riverine duck that has undergone serious declines. I used population and spatial modelling to answer three questions: (1) what are the threats to whio, (2) how can these threats be managed, and (3) managing which whio habitats will give the greatest conservation gain? A spatial analysis of contemporary whio habitat using boosted regression trees re- vealed whio are only secure in 1 % of their historical range, with predation likely causing significantly greater range contraction (83 %) than habitat modification (29 %). In that analysis, I identified 39,000 km of occupiable whio habitat, providing extensive oppor- tunities to expand their contemporary range through management. Intensive monitoring identified stoats (Mustela erminea) as the primary cause of whio population declines, with stoat predation severely reducing whio nest survival (10 % and 54 % in the absence and presence of stoat control, respectively). Population viability analyses indicated whio populations in the absence of stoat control were at high risk of extinction (λ = 0.74) but large-scale, low-intensity predator control was useful for short-term whio conservation. However, whio populations with stoat control still had a declining population growth rate (λ = 0.95) and further intervention may be required to prevent whio extinctions. Such management needs to target high quality habitat to ensure the greatest conservation value. Analyses of habitat quality revealed whio fitness was highest in warm, low gradient riv- 3 ers, although fitness gradients differed between North and South Islands. Comparisons of fitness relationships with spatial model predictions showed that South Island whio oc- curred more frequently in poorer habitat, indicating they may occupy a relict distribution. Limited resources for conservation mean identifying effective management tech- niques is critical for species persistence. My modelling approach enabled the effective- ness of whio management to be assessed and areas of high quality habitat where such management should provide the greatest benefit to be identified. These tools are directly applicable to the conservation management of many threatened species by quickly in- forming managers in situations where distributions may not follow habitat quality. 4 7 Preface Conservation management, like emergency medicine, involves making difficult decisions about the allocation of scarce resources wisely to preserve valuable life (Bottrill et al. 2008, 2009). Managers are frequently required to make immediate responses to prevent further declines of imperilled populations, often in the absence of detailed information (Grantham et al. 2009). Consequently, population distribution patterns are often used to guide conservation decisions. However, distribution patterns may be misleading if threats have restricted species to low quality habitat (van Horne 1983, Battin 2004). This issue means it is not always apparent where management efforts should be concentrated for maximum conservation gain. Conservation that targets inappropriate threats or un- dertakes management in low quality habitat may risk wasting limited resources or, in worst-case scenarios, result in continuing population declines despite management ef- forts (Crouse et al. 1987, Doak et al. 1994, Keedwell et al. 2002). Therefore, effective conservation requires clear identification of high quality habitat, where threatened species should respond most quickly to management (Sergio and Newton 2003), and the threats present within that habitat (Moilanen 2008, Briggs 2009). It is also vitally important to assess the effectiveness of management techniques through structured monitoring to en- sure that conservation efforts actually lead to increases in population viability (Stem et al. 2005). Failure to do so may be costly, both
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