The impact of increasing predation risk and declining food availability on the population dynamics and demography of a long-lived mesopredator Sarah Rose Hoy MSc Ecology, Evolution & Conservation, Imperial College London BSc Zoology (hons), University of Manchester 2015 A thesis presented for the degree of Doctor of Philosophy at the University of Aberdeen DECLARATION OF AUTHENTICITY I, Sarah Rose Hoy declare that the work presented in this thesis is my own, and has not been accepted in any previous applications for a degree. All quotations have been distinguished by quotation marks and all sources of information have been specifically acknowledged. Signed ____________________________ date____________________ AUTHOR CONTRIBUTIONS I am the first author of all chapters; Xavier Lambin, Alex Millon, Phil Whitfield and Steve Petty are contributing authors on Chapters 2-5. Mick Marquiss and Martin Davison were also contributing authors to Chapter 3. Jane Reid and Steve Redpath also made helpful suggestions on drafts of Chapter 3 and Jane also commented on Chapter 4. While the data used in the analyses has been collected by many people over the years (most notably by Steve Petty, David Anderson, Martin Davison and Brian Little), I collected all data on tawny owls and field voles between October 2011-October 2014 and also assisted with data collection on goshawks during this time. Steve Petty initiated the monitoring of goshawks, tawny owls and field voles and along with myself, Alex Millon and Xavier Lambin he played a role in designing the research carried out in this thesis. The chapters in this thesis have been written as a sequence of manuscripts, in preparation for publication and each has several smaller objectives, summarised below. Chapter 3 was published in 2014, as a research article entitled ‘Age and sex-selective predation moderate the overall impact of predators’ in the Journal of Animal Ecology. i TABLE OF CONTENTS TABLE OF CONTENTS DECLARATION OF AUTHENTICITY ............................................................................ i AUTHOR CONTRIBUTIONS ............................................................................................ i TABLE OF CONTENTS .................................................................................................... ii ACKNOWLEDGEMENTS ................................................................................................ 1 THESIS ABSTRACT .......................................................................................................... 3 CHAPTER 1 ......................................................................................................................... 5 GENERAL INTRODUCTION ....................................................................................................... 5 General background ................................................................................................................... 6 Thesis objectives & structure ................................................................................................... 11 Chapter summaries ................................................................................................................... 11 Study system ............................................................................................................................ 15 Proxies of food availability and predation risk ......................................................................... 18 CHAPTER 2 ....................................................................................................................... 20 IS FOOD-LIMITATION CAUSING A RECOVERING POPULATION OF NORTHERN GOSHAWKS ACCIPITER GENTILIS TO PREY MORE ON RAPTORS? ............................... 20 Adult goshawk plucking on a partridge.................................................................................... 20 Abstract .................................................................................................................................... 21 Introduction .............................................................................................................................. 21 Methods .................................................................................................................................... 24 Results ...................................................................................................................................... 29 Discussion ................................................................................................................................ 44 Acknowledgements .................................................................................................................. 50 CHAPTER 3 ....................................................................................................................... 51 AGE AND SEX-SELECTIVE PREDATION MODERATE THE OVERALL IMPACT OF PREDATION ................................................................................................................................ 51 Abstract .................................................................................................................................... 52 Introduction .............................................................................................................................. 52 Methods .................................................................................................................................... 56 Results ...................................................................................................................................... 61 Discussion ................................................................................................................................ 69 Acknowledgements .................................................................................................................. 73 CHAPTER 4 ....................................................................................................................... 74 INCREASING PREDATION RISK ALTERS THE TRADE-OFF BETWEEN REPRODUCTION AND SURVIVAL FOR SENESCENT INDIVIDUALS ............................. 74 Abstract .................................................................................................................................... 75 Introduction .............................................................................................................................. 75 Methods .................................................................................................................................... 77 Results ...................................................................................................................................... 81 Discussion ................................................................................................................................ 87 Acknowledgements .................................................................................................................. 90 ii TABLE OF CONTENTS CHAPTER 5 ....................................................................................................................... 91 THE INFLUENCE OF INTRINSIC AND EXTRINSIC (FOOD AVAILABILITY AND PREDATION RISK) PROCESSES ON THE REPRODUCTIVE DECISIONS OF A LONG- LIVED PREY SPECIES ............................................................................................................... 91 Abstract .................................................................................................................................... 92 Introduction .............................................................................................................................. 92 Methods .................................................................................................................................... 95 Results .................................................................................................................................... 100 Discussion .............................................................................................................................. 105 Acknowledgements ................................................................................................................ 111 CHAPTER 6 ..................................................................................................................... 112 GENERAL DISCUSSION ......................................................................................................... 112 Thesis summary ...................................................................................................................... 113 Validation of proxies .............................................................................................................. 113 The impact of food availability and predation risk on population dynamics, recruitment and immigration ............................................................................................................................ 115 The impact of variation in predation risk and food availability on survival, senescence and the strength of life-history trade-offs ........................................................................................... 117 The impact of top-down and bottom-up processes on owl breeding decisions and reproductive strategies. ................................................................................................................................ 121 Final remarks .........................................................................................................................