A global study of the distribution and richness of alien bird species Ellie E. Dyer A dissertation submitted for the degree of Doctor of Philosophy University College London Centre for Biodiversity and Environment Research (CBER) within the Department of Genetics, Evolution and Environment (GEE) University College London November 4, 2015 Declaration I, Ellie Eveness Dyer, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. Ellie Dyer, 4th November 2015 2 Abstract Alien species are a major component of human-induced environmental change, yet spatial and temporal variation in the drivers of their introduction, and their subsequent distribution and richness, are poorly understood. Here, I present a global analysis of the drivers of this variation for a major animal group, birds (Class Aves), using the newly-created Global Avian Invasions Atlas (GAVIA) database. GAVIA includes information on introduction successes and failures, enabling me to examine the effect of colonisation pressure (the number of species introduced) on alien bird distributions. A description of the GAVIA database is given in Chapter 2, with details on its scope and sources, data collation and validation, and the production of alien range maps. Chapter 3 focuses on the early stages of the invasion pathway, and shows that historical introductions tend to originate in Europe, were driven by the global movements of British colonialism, and involved species deemed useful. Modern introductions, in contrast, tend to originate in Southeast Asia and Africa, are driven by factors associated with wealth, and involve species found in the pet trade. Chapter 4 identifies colonisation pressure as the principal determinant of alien bird species richness at a global scale. Additional anthropogenic factors (residence time, distance to historic port) and environmental variables (temperature range, precipitation) also influence richness. Chapter 5 analyses the factors influencing alien geographic range size, with species achieving a larger alien range if they have been introduced more often, have a larger native range and a shorter residence time. Chapter 6 examines latitudinal patterns of alien species richness and range size, and the likelihood of failure relative to latitude and native range limits. Overall, I demonstrate that alien bird distributions are primarily driven by anthropogenic influences, and highlight in particular the importance of incorporating a measure of colonisation pressure into studies of invasion. 3 Acknowledgements I would like to thank my supervisors: Phill Cassey for welcoming me to Adelaide and offering me endless advice and wine (or advice and endless wine?), and for feeding me delicious gluten-free barbeque cuisine; Ben Collen for being a calming influence, a voice of reason and a good friend; Kate Jones for her insights and guidance, and for making me laugh when I wanted to cry; and Tim Blackburn for getting me started on this alien bird journey in the first place, and offering advice and encouragement (and more wine) every step of the way. I am extremely grateful to the hundreds of ornithological experts around the world who shared their local knowledge on alien birds with me, and those who went out of their way to assist me in finding the information that I needed. The GAVIA database would not have been nearly as comprehensive without their help. I would like to extend a special thank you to Dan Richman, who spent many long afternoons with me designing the original structure of the GAVIA database. Getting it right from the start has helped enormously in the long run. I would like to thank my colleagues in the Institute of Zoology at the Zoological Society of London. Those that helped with GAVIA in the beginning: Victoria Franks, Fiona Spooner, Elizabeth Jones, Rebecca Herdson and Frances Davies. Those that have supported me during my thesis: Xavier Harrison, Mike Hudson and Robin Freeman. And those that made me look forward to going into the office every day: Monika Bohm, Patricia Brekke, Jessica Bryant, Frances Clare, Alanna Collen, Jennifer Crees, Nadia Dewhurst-Richman, Clare Duncan, Dada Gottelli and Kirsten McMillan. I would like to thank my colleagues at UCL, in particular Chris Langridge, David Redding, Henry Ferguson-Gow, Roee Maor, Tim Lucas, David Murrell, and Prabu Siva. I would no doubt have thrown my computer out of the window without your help. I would like to thank the team at the University of Adelaide: Miquel Val Illosera, Pablo Garcia Diaz, Talia Wittmann, and many others. Also I would like to make a special mention of Su Shan, for being a great friend and support during both trips to Adelaide and throughout my PhD. I have had such fun working with you. 4 To my parents: Chris and Jeannie – thank you for always encouraging and believing in me, and for staying up past midnight to help me produce a certain difficult figure! To the rest of my family: Jessie, Joel, Indi, Vivi and Alba, and my friends Cathryn and Helena – thank you for your support, endless cups of tea and soothing words, and for putting up with the hysteria and the many months of ‘I’m really nearly there…!’ The last three years would have been a great deal more difficult had I not been able to escape to you. And lastly my biggest thanks go to David. My anchor, my best friend, my adventurer. I could not have gotten this far without your never-ending encouragement, patience and laughter. Two PhDs, two kittens, eleven countries, and buying and renovating a house and garden is not too shabby for four years of teamwork. 5 Contents Declaration .................................................................................................................. 2 Abstract ....................................................................................................................... 3 Acknowledgements .................................................................................................... 4 List of figures .............................................................................................................. 9 List of tables ............................................................................................................. 15 Attribution ................................................................................................................. 19 Chapter 1. Introduction ........................................................................................... 20 1.1 The Invasion Pathway ...................................................................................... 20 1.1.1 Overview.................................................................................................... 20 1.1.2 Birds as a focal taxon................................................................................. 22 1.1.3 Transport and Introduction ......................................................................... 22 1.1.4 Establishment ............................................................................................ 26 1.1.5 Spread ....................................................................................................... 28 1.1.6 Impacts of alien species ............................................................................. 30 1.2 The Global Avian Invasions Atlas (GAVIA) ....................................................... 31 1.3 Thesis overview ................................................................................................ 32 Chapter 2. The GAVIA database: a global database of alien bird introductions . 34 2.1 Introduction ...................................................................................................... 34 2.2 Methods ........................................................................................................... 35 2.2.1 Data compilers ........................................................................................... 35 2.2.2 Criteria for data inclusion ........................................................................... 36 2.2.3 Data searches ........................................................................................... 36 2.2.4 Database design ........................................................................................ 38 2.2.5 Data entry .................................................................................................. 42 2.2.6 Taxonomic names and classification .......................................................... 47 2.2.7 Biogeographical coverage ......................................................................... 48 2.2.8 Distribution range maps ............................................................................. 50 2.2.9 Cross validation between database and distribution maps ......................... 52 2.3 Results ............................................................................................................. 53 2.4 Discussion ........................................................................................................ 60 6 Chapter 3. Temporal change of global drivers of alien bird introductions .......... 62 3.1 Introduction ...................................................................................................... 62 3.2 Methods ........................................................................................................... 66 3.2.1 Data ..........................................................................................................