Increased human-induced environmental changes and global warming alter bird migration timing and routes. Recently, many Holarctic species, including white storks, Ciconia ciconia, were reported to overwinter at higher latitudes, closer to breeding grounds. We aimed to understand the causes and implications of this phenomenon by examining bird survival and behaviour during overwintering in Europe versus Africa. We compared GPS and body acceleration data of 54 juvenile (first-year) white storks that originated from the same European natal population and overwintered in Europe or Africa. All six juveniles that overwintered in Europe survived through their first year, which was significantly higher than only 38% of the 48 overwintering in the species' traditional grounds in Africa. During overwintering, storks in Europe differed from those in Africa by (1) reducing movement and foraging range, (2) spending less time flying and more time resting, thus using less energy (estimated from overall dynamic body acceleration) and (3) reducing foraging effort, while relying more on anthropogenic resources (landfills and agricultural areas). Timing affected overwintering site as juveniles that overwintered in Europe hatched and started migrating later. We emphasize, however, that late hatching by itself did not yield a survival benefit as not all late juveniles curtailed their migration. We suggest that wintering in Europe was less demanding compared to Africa which may explain the increased survival of juveniles that wintered in Europe. Our findings correspond to the general increase in the European wintering population of white storks, and shed light on the contemporary trend of shortened bird migration; a phenomenon with potentially broad ecological implications.
Bibliographical noteFunding Information:
We thank S. Wohlfahrt, A. Hinz, P. Wevers and M. Meinel from the University of Potsdam for conducting the field observations, T. Schaffer, H.G. Benecke and W. Sender and his crew in the Drömling Nature Park for their essential help in the field work in Germany, H. Schmid, H. Eggers, G. Sterzer and N. Aljadeff for their help in the data downloading, R. Harel for advising in all the research aspects, O. Hatzofe from the Israel Nature and Parks Authority and B. Keeves from the Max-Planck-Institute for Ornithology for their help in retrieving lost transmitters and W. Heidrich and F. Kuemmeth from e-obs GmbH for their dedicated technical support. We acknowledge the generous funding of DIP grants (DFG) NA 846/1-1 and WI 3576/1-1 to R.N., F.J. and M.W. This study was also supported by the Minerva Center for Movement Ecology granted to R.N. S.R. was supported by a doctoral bird study scholarship of the Ministry of Science and Technology, Israel. D.Z. received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA grant agreement no. 624958.
© 2017 The Association for the Study of Animal Behaviour
- Ciconia ciconia
- bird migration
- shortening migration
- white stork
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Animal Science and Zoology