Ocean-wide drivers of migration strategies and 1 their influence on population breeding 2 performance in a declining seabird 3 4

9 1 Department of Zoology, University of Oxford, Radcliffe Observatory Quarter, Woodstock Road, Oxford, OX2 6GG, UK 10 2 Institute of Zoology, Zoological Society of London, Regent’s Park, London NW1 4RY, UK 11 3 Norwegian Institute for Nature Research, P.O. Box 5685 Torgard, NO-7485 Trondheim, Norway 12 4 Atlantic Laboratory for Avian Research, University of New Brunswick, PO Box 4400, Fredericton, NB E3B 5A3, Canada 13