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Magnetic compass of migratory Savannah sparrows is calibrated by skylight polarizarion and sunrise and sunset

Author:
  • Rachel Muheim
  • Susanne Åkesson
  • John Phillips
Publishing year: 2007
Language: English
Pages: 485-494
Publication/Series: Journal für Ornithologie1852-12-31+01:002004-01-01+01:00
Volume: 148
Issue: Supplement 2
Document type: Journal article
Publisher: Springer

Abstract english

Migratory birds use compass systems derived from the geomagnetic field, the stars, the sun and polarized light patterns. We tested whether birds use a single underlying reference system for calibration of these compasses and, specifically, whether sunset and sunrise polarized light cues from the region of the sky near the horizon are used to calibrate the magnetic compass. We carried out orientation experiments with Savannah sparrows, Passerculus sandwichensis, in Alaska during autumn migration 2005, and compared the magnetic orientations of individual birds before and after exposure to conflicting information between magnetic and celestial cues. Birds exposed to an artificially shifted polarization pattern (±90° shift relative to the natural condition) for 1 h at local sunrise or sunset recalibrated their magnetic compass, but only when given access to the artificial polarization pattern near the horizon. Birds exposed to a 90° clockwise-shifted magnetic field for 1 h at solar noon did not recalibrate their magnetic compass. These results indicate that migratory birds calibrate their magnetic compass using the skylight polarization pattern vertically intersecting the horizon at sunrise and sunset. In conjunction with earlier work showing that sun and star compass calibrations are secondarily derived from magnetic and polarized light cues, our findings suggest that polarized light cues near the horizon at sunrise and sunset provide the primary calibration reference for the compass systems of migratory songbirds.

Keywords

  • Biological Sciences
  • Zoology
  • Orientation - Cue calibration - Magnetic compass - Skylight polarization

Other

Published
  • ISSN: 1439-0361
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