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Fuel reserves affect migratory orientation of thrushes and sparrows both before and after crossing an ecological barrier near their breeding grounds

Author:
  • Mark E. Deutschlander
  • Rachel Muheim
Publishing year: 2009
Language: English
Pages: 85-89
Publication/Series: Journal of Avian Biology
Volume: 40
Issue: 1
Document type: Journal article
Publisher: Federation of European Neuroscience Societies and Blackwell Publishing Ltd

Abstract english

Fat reserves influence the orientation of migrating songbirds at ecological barriers, such as expansive water crossings. Upon encountering a body of water, fat migrants usually cross the barrier exhibiting 'forward' migration in a seasonally appropriate direction. In contrast, lean birds often exhibit temporary 'reverse' orientation away from the water, possibly to lead them to suitable habitats for refueling. Most examples of reverse orientation are restricted to autumn migration and, in North America, are largely limited to transcontinental migrants prior to crossing the Gulf of Mexico. Little is known about the orientation of lean birds after crossing an ecological barrier or on the way to their breeding grounds. We examined the effect of fat stores on migratory orientation of both long- and short-distance migrants before and after a water crossing near their breeding grounds; Catharus thrushes (Swainson's and gray-cheeked thrushes, C. ustulatus and C. minimus) and white-throated sparrows Zonotrichia albicollis were tested for orientation at the south shore of Lake Ontario during spring and autumn. During both spring and autumn, fat birds oriented in a seasonally appropriate, forward direction. Lean thrushes showed a tendency for reverse orientation upon encountering water in the spring and axial, shoreline orientation after crossing water in the autumn. Lean sparrows were not consistently oriented in any direction during either season. The responses of lean birds may be attributable to their stopover ecology and seasonally-dependent habitat quality.

Keywords

  • Zoology

Other

Published
  • ISSN: 0908-8857
Rachel Muheim
E-mail: rachel.muheim [at] biol.lu.se

Researcher

Functional zoology

+46 46 222 31 93

B-B314

4

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