Acknowledgements
Thanks to Patrick Manley, Damien Haberlin, Dave Boyle, Ben Dean, and Holly Kirk for field assistance. Fergus McCormick and the Office of Public Works facilitated fieldwork on Skellig Michael, and Chris Taylor and the Wildlife Trust for South and West Wales facilitated work on Skomer. The SEATRACK programme provided numerous tracking devices, as well as curating and processing data from Skellig Michael. Thanks to Debra Dial of the National Aquarium, USA, Meret Huwiler of TierPark Bern, Switzerland, and Ana Fereira and Irene Sempere of Oceanário de Lisboa, Portugal, for insights into the behaviour and phenology of captive puffins. JD was funded by the Irish Research Council as an Enterprise Partnership Grant, cofounded by the Petroleum Infrastructure Program (EPSPG/2019/469). Work on Skomer was supported by the Mary Griffiths award. The authors declare no conflict of interest.