Acknowledgements
We thank the Lundy Company and the Lundy Field Society for their continuous support in the Lundy Sparrow Project, and numerous field assistants and master students for field data collection. HYJC was funded by a PhD scholarship from the University of Groningen and Macquarie University. JS received funding from the European Research Council (PCIG12-GA-2012-333096). TB, MJPS and JS were supported by the Natural and Environmental Research Council (grant NE/J024567/1). HD was supported by a Rosalind Franklin Fellowship from the University of Groningen.