caa a22 4500 46317545X CHVBK 20180406164824.0 cr unu---uuuuu 170326e20071201xx s 000 0 eng 10.1007/s10336-007-0187-4 doi (NATIONALLICENCE)springer-10.1007/s10336-007-0187-4 Magnetic compass of migratory Savannah sparrows is calibrated by skylight polarization at sunrise and sunset [Elektronische Daten] [Rachel Muheim, Susanne Åkesson, John Phillips] 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 1h 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 1h 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. Dt. Ornithologen-Gesellschaft e.V., 2007 Orientation nationallicence Cue calibration nationallicence Magnetic compass nationallicence Skylight polarization nationallicence Muheim Rachel Department of Biological Sciences, Virginia Polytechnic Institute and State University, Derring Hall, 24061, Blacksburg, VA, USA aut Åkesson Susanne Department of Animal Ecology, Lund University, Ecology Building, 223 62, Lund, Sweden aut Phillips John Department of Biological Sciences, Virginia Polytechnic Institute and State University, Derring Hall, 24061, Blacksburg, VA, USA aut Journal of Ornithology Springer-Verlag 148(2007-12-01), 485-494 0021-8375 148<485 2007 148 10336 https://doi.org/10.1007/s10336-007-0187-4 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10336-007-0187-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Muheim Rachel Department of Biological Sciences, Virginia Polytechnic Institute and State University, Derring Hall, 24061, Blacksburg, VA, USA aut NATIONALLICENCE 700 1- Åkesson Susanne Department of Animal Ecology, Lund University, Ecology Building, 223 62, Lund, Sweden aut NATIONALLICENCE 700 1- Phillips John Department of Biological Sciences, Virginia Polytechnic Institute and State University, Derring Hall, 24061, Blacksburg, VA, USA aut NATIONALLICENCE 773 0- Journal of Ornithology Springer-Verlag 148(2007-12-01), 485-494 0021-8375 148<485 2007 148 10336 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer