Acknowledgements
We thank the Seychelles Bureau of Standards and the Department of Environment for permission for fieldwork overall, and Nature Seychelles (Cousin), the Island Conservation Society (Aride) and the proprietors of Cousine, Denis and Frégate for facilitating fieldwork on their respective islands. This study would not have been possible without the contribution of many fieldworkers and technicians. We particularly thank David Wright and Marco van der Velde for MHC and Microsatellite genotyping, respectively. CSD was funded by the Natural Environment Research Council and EnvEast DTP (NE/L002582/1). The long-term Seychelles warbler study was funded by various grants including a Marie Curie Fellowship (HPMF‐CT‐2000–01074), NERC fellowship (NER/I/S/2002/00712), NERC Grants NE/F02083X/1 and NE/K005502/1 to DSR, NERC fellowship (NE/I021748/1) to HLD, NERC grant NE/P011284/1 to HLD and DSR, NWO VENI fellowship (863.15.020) to MH and NWO Grants 854.11.003 and 823.01.014 to JK.