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Response of a free-flying songbird to an experimental shift of the light polarization pattern around sunset

Author:
  • Heiko Schmaljohann
  • Tobias Rautenberg
  • Rachel Muheim
  • Beat Naef-Daenzer
  • Franz Bairlein
Publishing year: 2013
Language: English
Pages: 1381-1387
Publication/Series: Journal of Experimental Biology
Volume: 216
Issue: 8
Document type: Journal article
Publisher: The Company of Biologists Ltd

Abstract english

The magnetic field, the sun, the stars and the polarization pattern of visible light during twilight are important cues for orientation in nocturnally migrating songbirds. As these cues change with time and location on Earth, the polarization pattern was put forward as a likely key reference system calibrating the other compass systems. Whether this applies generally to migratory birds is, however, controversially discussed. We used an experimental approach in free-flying birds to study the role of polarization for their departure direction in autumn. Experimental birds experienced a 90 deg shift of the band of maximum polarization during sunset, whereas control birds experienced the polarization pattern as under natural conditions. Full view of the sunset cues near the horizon was provided during the cue conflict exposure. Here we show that both the experimental and the control birds being released after nautical twilight departed consistently towards south-southeast. Radiotelemetry allowed tracking of the first 15 km of the birds' outward journey, thus the intrinsic migration direction as chosen by the birds was measured. We found no recalibration of the magnetic compass after pre-exposure to a cue conflict between the natural magnetic field and the artificially shifted polarization pattern at sunset. The lacking difference in the departure direction of both groups may suggest that birds did not recalibrate any of the compass systems during the experiment. As free-flying migrants can use all available orientation cues after release, it remains unknown whether our birds might have used the magnetic and/or star compass to determine their departure direction.

Keywords

  • Zoology
  • cue conflict
  • magnetic compass
  • migration
  • orientation
  • polarization
  • pattern
  • radiotelemetry
  • songbird
  • star compass

Other

Published
  • ISSN: 1477-9145
Rachel Muheim
E-mail: rachel [dot] muheim [at] biol [dot] lu [dot] 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