Individual spatial consistency and dietary flexibility in the migratory behavior of northern gannets wintering in the Northeast Atlantic

• Published in: Frontiers in Ecology and Evolution
• Main Authors: Grecian, W. James, Williams, Hannah J., Votier, Stephen C., Bearhop, Stuart, Cleasby, Ian R., Grémillet, David, Hamer, Keith C., Le Nuz, Mélanie, Lescroël, Amélie, Newton, Jason, Patrick, Samantha C., Phillips, Richard A., Wakefield, Ewan D., Bodey, Thomas W.
• Other Authors: University of St Andrews. School of Biology, University of St Andrews. Scottish Oceans Institute, University of St Andrews. Sea Mammal Research Unit
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: Individual variation; Carry-over effects; Geolocator (GLS); Stable isotope analysis (SIA); Animal migration; QH301 Biology; DAS; QH301; Northeast Atlantic
• Online Access: http://hdl.handle.net/10023/17888; https://doi.org/10.3389/fevo.2019.00214

Funding: UK Natural Environment Research Council (NERC Standard Grant NE/H007466/1). SB is currently funded by an ERC consolidator’s grant (310820: STATEMIG). EW is funded by the NERC (Independent Research Fellowship NE/M017990/1). Migration is a fundamental behavioral process prevalent among a wide variety of animal taxa. As individuals are increasingly shown to present consistent responses to environmental cues for breeding or foraging, it may be expected that approaches to migration would present similar among-individual consistencies. Seabirds frequently show consistent individual differences in a range of traits related to foraging and space-use during both the breeding and non-breeding seasons, but the causes and consequences of this consistency are poorly understood. In this study, we combined analysis of geolocation and stable isotope data across multiple years to investigate individual variation in the non-breeding movements and diets of northern gannets Morus bassanus, and the consequences for changes in body condition. We found that individuals were highly repeatable in their non-breeding destination over consecutive years even though the population-level non-breeding distribution spanned >35° of latitude. Isotopic signatures were also strongly repeatable, with individuals assigned to one of two dietary clusters defined by their distinct trophic (δ15N) and spatial (δ13C) position. The only non-breeding destination in which the two dietary clusters co-occurred was off the coast of northwest Africa. The majority of individuals adopted a consistent foraging strategy, as they remained within the same dietary cluster across years, with little variation in body mass corrected for size among these consistent individuals. In contrast, the few individuals that switched clusters between years were in better condition relative to the rest of the population, suggesting there may be benefits to flexibility during the non-breeding period. Our results indicate that a consistent migratory strategy can be ...