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Obligatory barrier crossing and adaptive fuel management in migratory birds: the case of Atlantic crossing in Northern Wheatears

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Author

Summary, in English

Behaviour on migration was often suggested to be selected for time-minimising strategies. Current optimality models predict that optimal fuel loads at departure from stopover sites should increase with increasing fuel deposition rates. We modified such models for the special case of the east Atlantic crossing of the Northern Wheatear (Oenanthe oenanthe). From optimality theory, we predict that optimal time-minimising behaviour in front of such a barrier should result in a positive correlation between fuel deposition rates and departure fuel loads only above a certain threshold, which is the minimum fuel load (f(min)) required for the barrier crossing. Using a robust range equation, we calculated the minimum fuel loads for different barrier crossings and predict that time-minimising wheatears should deposit a minimum of 24% fuel in relation to lean body mass (m (0)) for the sea crossing between Iceland and Scotland. Fuel loads of departing birds in autumn in Iceland reached this value only marginally but showed positive correlation between fuel deposition rate (FDR) and departure fuel load (DFL). Birds at Fair Isle (Scotland) in spring, which were heading towards Iceland or Greenland, were significantly heavier and even showed signs of overloading with fuel loads up to 50% of lean body mass. Departure decisions of Icelandic birds correlated significantly with favourable wind situations when assuming a migration direction towards Spain; however, the low departure fuel loads contradict a direct non-stop flight.

Publishing year

2008

Language

English

Pages

1069-1078

Publication/Series

Behavioral Ecology and Sociobiology

Volume

62

Issue

7

Document type

Journal article

Publisher

Springer

Topic

  • Biological Sciences

Keywords

  • flight costs
  • barrier crossing
  • optimal migration
  • Oenanthe oenanthe
  • fuel loads

Status

Published

ISBN/ISSN/Other

  • ISSN: 1432-0762