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Skipping the Baltic: the emergence of a dichotomy of alternative spring migration strategies in Russian barnacle geese

Author:
  • Goetz Eichhorn
  • Rudolf H. Drent
  • Julia Stahl
  • Aivar Leito
  • Thomas Alerstam
Publishing year: 2009
Language: English
Pages: 63-72
Publication/Series: Journal of Animal Ecology
Volume: 78
Issue: 1
Document type: Journal article
Publisher: Federation of European Neuroscience Societies and Blackwell Publishing Ltd

Abstract english

Since the early 1990s, an increasing proportion of barnacle geese, Branta leucopsis, bound for breeding sites in the Russian Arctic delay their departure from the wintering quarters in the Wadden Sea by 4 weeks. These late-migrating geese skip spring stopover sites in the Baltic traditionally used by the entire population. Individual geese from an arctic colony tracked by satellite or light-level geolocators during spring migration in 2004 and 2005 predominantly followed the new strategy, but a minority still maintained the traditional pattern. Despite a spread of more than 50 days in departure date from the Wadden Sea, both early and late departing females laid their eggs within the short time-window conferring breeding success. The spread of these new migration routines coincided with a strong increase of overall numbers and the exploitation of new spring staging resources in the Wadden Sea. Counts from Estonia demonstrate that numbers have levelled off recently at the Baltic staging sites, suggesting that the capacity of these staging sites in spring has been reached. Although onset of spring affects migratory timing in barnacle geese, it cannot explain the observed delay in departure from the wintering grounds. We hypothesize that the new migratory strategy has evolved in response to increased competition for food at spring staging sites in the Baltic. According to an analytical model of optimal migration, the geese should skip the Baltic whenever the energy deposition rate falls below 88% of the Wadden Sea value.

Keywords

  • Biological Sciences
  • tracking
  • migratory timing
  • global change
  • arctic breeding
  • geolocation

Other

Published
  • ISSN: 1365-2656
Thomas Alerstam
E-mail: thomas.alerstam [at] biol.lu.se

Professor emeritus

Evolutionary ecology

+46 46 222 37 85

E-C225

Sölvegatan 37, Lund

50

Centre for Animal Movement Research
Evolutionary Ecology, Department of Biology
Ecology building S-223 62 Lund Sweden