Funding statement
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.
Conflict of interest disclosure: The authors declare no conflicts of interest.
Ethics approval: All animal procedures are licensed and approved by the British Trust for Ornithology and the UK Home Office (Project License PP5873078).