Resource tracking within and across continents in long-distance bird migrants

Abstract
Migratory birds track seasonal resources across and between continents. We propose a general strategy of tracking the broad seasonal abundance of resources throughout the annual cycle in the longest-distance migrating land birds as an alternative to tracking a certain climatic niche or shorter-term resource surplus occurring, for example, during spring foliation. Whether and how this is possible for complex annual spatiotemporal schedules is not known. New tracking technology enables unprecedented spatial and temporal mapping of long-distance movement of birds. We show that three Palearctic-African species track vegetation greenness throughout their annual cycle, adjusting the timing and direction of migratory movements with seasonal changes in resource availability over Europe and Africa. Common cuckoos maximize the vegetation greenness, whereas red-backed shrikes and thrush nightingales track seasonal surplus in greenness. Our results demonstrate that the longest-distance migrants move between consecutive staging areas even within the wintering region in Africa to match seasonal variation in regional climate. End-of-century climate projections indicate that optimizing greenness would be possible but that vegetation surplus might be more difficult to track in the future.

Citation
Thorup K, Tøttrup AP, Willemoes M, Klaassen RHG, Strandberg R, et al. (2017) Resource tracking within and across continents in long-distance bird migrants. Science Advances 3: e1601360. Available: http://dx.doi.org/10.1126/sciadv.1601360.

Acknowledgements
K.T. thanks the Danish Council for Independent Research for support to the MATCH project (1323-00048B). K.T., A.P.T., M.W., M.L.V., M.B.A., and C.R. thank the Danish National Research Foundation for support to the Center for Macroecology, Evolution and Climate (DNRF96). H.P.D. and M.B.A. also acknowledge support from IC&DT Project (1/SAESCTN/ALENT-07-0224-FEDER-001755).

Publisher
American Association for the Advancement of Science (AAAS)

Journal
Science Advances

DOI
10.1126/sciadv.1601360

Additional Links
http://advances.sciencemag.org/content/3/1/e1601360.full

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