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Journal of Ornithology

, Volume 147, Issue 2, pp 122–134 | Cite as

Travelling to breed

  • Rudolf H. DrentEmail author
  • Anthony D. Fox
  • Julia Stahl
Review

Abstract

Traditionally, investigation of the dynamics of avian migration has been heavily biased towards the autumn return trip to the wintering quarters. Since the migratory prelude to breeding has direct fitness consequences, the European Science Foundation recently redressed the balance and sponsored a workshop on spring travels. We here survey the findings elucidating the complications arising during migration directed towards the breeding quarters. The evidence that early nesting confers advantage is overwhelming, hence demands of reproduction pose a constraint on both time and energy resources during spring. Both during migration and upon arrival there must therefore be strong selection in favour of saving time. Experimental results (e.g. using supplementary feeding) show that the date of laying is generally proximately constrained by the inability of the female to find sufficient nutrients. A key question thus concerns the implementation of the ‘capital’ strategy for breeding, the female accumulating nutrient stores along the way to bridge periods of shortage upon arrival on the breeding grounds. Eight studies on waterfowl (geese and eiders) and shorebirds (turnstones and knots) nesting in the arctic combine tracking of individuals (satellite telemetry) with direct observation (marked birds) and reconstruction of the origin of nutrients laid down in the eggs or in the form of body stores of the female parent (stable isotope signatures of tissues compared to potential food sources). The consensus emerges that in most cases a mixed strategy prevails, with nutrients garnered locally supplementing ‘imported’ body stores. The species concerned face a shortage of feeding time during incubation and suffer an energy deficit. Successful breeding thus depends on adequate fat depots that form part of the ‘capital’ the parents bring with them. Some headway has been made in predicting the extent of dependence on body stores for breeding in relation to body mass and length of migration from rates of fat deposition during stopover and fat consumption during flight for waterfowl. This work poses a challenge to refine field studies accordingly. The pressure to save time en route highlights the need to effectively exploit rich food resources. Several case studies underline the crucial significance of a very limited set of stopover sites, each with a narrow time window of optimal harvest. The influence of man at such sites often verges on the disastrous, and ongoing climate change may unhinge the finely tuned timing long-distance migrants depend on. There is a real need to extend this work to provide the scientific basis to underpin adequate conservation actions.

Keywords

Capital breeding Isotopic signature Migration connectivity Satellite tracking Spring stopover ecology 

Notes

Acknowledgements

The Travelling to Breed workshop was held during 21–23 November 2004 at the Wildlife Management School at Kalø in eastern Jutland, Denmark, and was successful thanks to the enthusiastic contributions of 53 active willing participants from 12 countries. The meeting was only possible because of financial support from the European Science Foundation Optimality in Bird Migration Programme (which supported accommodation costs of delegates to the meeting), the Danish Research Council (which funded participation of all non-European delegates) and the Netherlands Arctic Programme (which supported production of the proceedings in Ardea). We are extremely grateful to Else-Marie Nielsen (NERI) and the staff of the Wildlife Management School for organising such an excellent meeting, and to Rune Dietz and Jonas Teilmann (NERI) for their revelations on recent advances in the study of sea mammals which threw new light on similar questions relating to different taxa also “travelling to breed”. The authors are grateful to Jesper Madsen (NERI) and Franz Bairlein (IfV, initiator of the European Science Foundation programme BIRD) for their support and encouragement throughout.

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Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2006

Authors and Affiliations

  • Rudolf H. Drent
    • 1
    Email author
  • Anthony D. Fox
    • 2
  • Julia Stahl
    • 1
    • 3
  1. 1.Animal Ecology Group, Centre for Ecological and Evolutionary StudiesUniversity of GroningenHarenThe Netherlands
  2. 2.Department of Wildlife Ecology and BiodiversityNational Environmental Research InstituteRøndeDenmark
  3. 3.Landscape Ecology GroupUniversity of OldenburgOldenburgGermany

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