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

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Author

Summary, in 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.

Publishing year

2007

Language

English

Pages

485-494

Publication/Series

Journal of Ornithology

Volume

148

Issue

Supplement 2

Document type

Journal article

Publisher

Springer

Topic

  • Biological Sciences
  • Zoology

Keywords

  • Orientation - Cue calibration - Magnetic compass - Skylight polarization

Status

Published

Research group

  • Animal Navigation Lab

ISBN/ISSN/Other

  • ISSN: 2193-7206