Ecological Impacts of Metallic Starling Colonies in Tropical Queensland, Australia
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Ecological Impacts of Metallic Starling Colonies in Tropical Queensland, Australia Daniel James Deans Natusch A thesis submitted in fulfilment of requirements for the degree of Doctor of Philosophy School of Life and Environmental Sciences University of Sydney January 2017 SUPERVISOR STATEMENT This is to certify that I have been Daniel’s primary supervisor during his PhD candidature and have overseen the production of this thesis. In my opinion Daniel’s thesis is sufficiently well presented to be examined, and it does not exceed the prescribed word limit or any extended word limit for which prior approval has been granted. Rick Shine University of Sydney 9 December 2016 ii DECLARATION This is to certify that the content of this thesis is my own work. This thesis has not been submitted for any degree or other purposes. I certify that the intellectual content of this thesis is the product of my own work and that all the assistance received in preparing this thesis and sources have been acknowledged. Daniel James Deans Natusch Frogs Hollow 9 December 2016 iii PREFACE In accordance with current practice at the University of Sydney, this thesis is presented as a series of stand-alone manuscripts that have been prepared for submission, are currently in review, or have been published in scientific journals. There is unavoidable repetition of certain topics, including background information on the study species and field site. Furthermore, chapters have been formatted for their respective journals, thus some include supplementary material, which expands on aspects of the manuscript itself. Throughout my PhD I have collaborated with many individuals. However, the ideas are my own and the vast majority of work (including planning, designing, implementing, analysing, and writing) was undertaken by me under the guidance of my supervisor. To maintain transparency regarding the level of contribution from myself and collaborators, I have listed all co-authors along with the full reference of the published paper at the beginning of each chapter. Because of joint authorship the work presented in chapters is discussed as “we” instead of “I”. Those playing lesser roles have been acknowledged at the end of each chapter. Fieldwork for this project was conducted under the approval of the University of Sydney’s Animal Ethics Committee (protocol: L04/3-2013/3/5969), and the Queensland Department of Environment and Heritage Protection (permit: WISP12944313). iv ACKNOWLEDGEMENTS This thesis represents three years of research in remote Cape York Peninsula, which would not have been possible without the support, guidance and inspiration of many people. Conducting high-quality fieldwork in remote areas is not a simple task. My ability to do so was assisted by the following people, to whom I am sincerely grateful: Xavier and Jade Barker, Tine Hannibal, Bill Koutsamanis, Damian Lettoof, Martin Mayer, Lachlan McIntyre, Dale and Lea-ann Mears, Jivanildo Miranda, John Mulholland, Cheryl and Bully Sanders, Kye and Anna Shields and James Walker. An equally difficult task is designing research questions and protocols in ways that maximise your ability to generate answers. I was privileged to receive guidance in these tasks by Professor Rick Shine, with whom I have wanted to work since I was a child. In fulfilling this goal I have become a better learner, thinker and communicator – and hence a better scientist. Thanks to Rick for deftly nurturing these skills and providing me with the support needed to successfully complete this PhD. Thanks also to Greg Brown, by whom I was fortunate to be co-supervised. Thanks to Matt Greenlees for assistance with animal ethics forms, and Georgia Ward-Fear and Cameron Hudson for the laughs. Finally, Melanie Elphick deserves special thanks for helping me to ship gear around the country, smoothly navigate the remarkable University bureaucracy, and for always smiling (even virtually)! Many thanks to my parents, David Natusch and Mandy Deans, for encouraging me to follow my passion, and supporting me while I did so. Thanks to the Apudthama Land Trust and Gudang Traditional Owners for generously sharing their knowledge and allowing me to conduct this research on their country. This study was made possible through the generous funding of the Skyrail Rainforest Foundation, the Holsworth Wildlife Endowment, and the Australian Research Council. v The above people all helped in small (but significant) ways. However, this research would not have been possible without the unwavering help and support of my wife, Jessica Lyons. Jess was there for every step of this journey, and did an extraordinary amount of work in the field (capturing, measuring and tracking animals) and in motivating me (pushing me out the door each morning) to make this project the best it could be. Simply put, Jess’ support made this project so successful, and in my eyes she deserves the award of this degree as much as I do. Thank you. vi TABLE OF CONTENTS SUPERVISOR STATEMENT .......................................................................... ii DECLARATION .............................................................................................. iii PREFACE .......................................................................................................... iv ACKNOWLEDGEMENTS ............................................................................... v TABLE OF CONTENTS ................................................................................. vii ABSTRACT ........................................................................................................ 1 GENERAL INTRODUCTION ......................................................................... 4 LITERATURE CITED ...................................................................................... 6 THESIS SYNOPSIS ........................................................................................... 8 CHAPTER ONE Communally nesting migratory birds create ecological hot-spots in tropical Australia ............................................................................................................ 10 Abstract ........................................................................................................................ 11 Introduction ................................................................................................................. 12 Materials and Methods ................................................................................................ 13 Results ......................................................................................................................... 20 Discussion .................................................................................................................... 26 Acknowledgements ..................................................................................................... 29 Literature cited ............................................................................................................. 30 CHAPTER TWO Biotic interactions mediate the influence of bird colonies on vegetation and soil chemistry at aggregation sites ................................................................... 34 Abstract ........................................................................................................................ 35 Introduction ................................................................................................................. 36 Materials and Methods ................................................................................................ 38 Results ......................................................................................................................... 45 Discussion .................................................................................................................... 54 Acknowledgements ..................................................................................................... 59 Literature cited ............................................................................................................. 60 CHAPTER THREE How do predators and scavengers locate widely-scattered resource hotspots within a tropical forest? ................................................................................... 66 Abstract ........................................................................................................................ 67 Introduction ................................................................................................................. 68 Materials and Methods ................................................................................................ 70 Results ......................................................................................................................... 76 Discussion .................................................................................................................... 81 Acknowledgements ..................................................................................................... 84 Literature cited ............................................................................................................. 84 vii CHAPTER FOUR Safety first: terrestrial predators drive selection of highly specific nesting sites in colonial-breeding birds ........................................................................ 87 Abstract .......................................................................................................................