title: The cost of migration: spoonbills suffer higher mortality during trans-Saharan spring migrations only.
abstract: Explanations for the wide variety of seasonal migration patterns of animals all carry the assumption that migration is costly and that this cost increases with migration distance. Although in some studies, the relationships between migration distance and breeding success or annual survival are established, none has investigated whether mortality during the actual migration increases with migration distance. Here, we compared seasonal survival between Eurasian spoonbills (Platalea leucorodia leucorodia) that breed in The Netherlands and migrate different distances (ca 1000, 2000 and 4500 km) to winter in France, Iberia and Mauritania, respectively. On the basis of resightings of individually marked birds throughout the year between 2005 and 2012, we show that summer, autumn and winter survival were very high and independent of migration distance, whereas mortality during spring migration was much higher (18%) for the birds that wintered in Mauritania, compared with those flying only as far as France (5%) or Iberia (6%). As such, this study is the first to show empirical evidence for increased mortality during some long migrations, likely driven by the presence of a physical barrier (the Sahara desert) in combination with suboptimal fuelling and unfavourable weather conditions en route.
authors.affiliation: Chair in Global Flyway Ecology, Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, PO Box 11103, 9700 CC Groningen, The Netherlands Department of Marine Ecology, NIOZ Royal Netherlands Institute for Sea Research, PO Box 59, 1790 AB Den Burg, Texel, The Netherlands tamarlok@gmail.com.
authors.forename: Tamar
authors.identifier: http://orcid.org/0000-0003-3753-8501
authors.initials: T
authors.lastname: Lok
authors.affiliation: Werkgroep Lepelaar, 9166 NZ Schiermonnikoog, The Netherlands.
authors.forename: Otto
authors.initials: O
authors.lastname: Overdijk
authors.affiliation: Chair in Global Flyway Ecology, Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, PO Box 11103, 9700 CC Groningen, The Netherlands Department of Marine Ecology, NIOZ Royal Netherlands Institute for Sea Research, PO Box 59, 1790 AB Den Burg, Texel, The Netherlands.
authors.forename: Theunis
authors.initials: T
authors.lastname: Piersma
mesh_terms: D000352:Africa, Northern; D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D001717:Birds / Q000502:physiology*; D005060:Europe; D008435:Mauritania; D009026:Mortality; D012621:Seasons
keywords: Sahara desert; differential migration; evolution of migration; long-distance migration; mark–recapture analysis; seasonal survival