Light-dependent magnetoreception in birds: does directional information change with light intensity?
Magnetic compass orientation in birds is based on light-dependent processes, with magnetoreception being possible only under light containing blue and green wavelengths. To look for possible intensity-dependent effects we tested Australian silvereyes during autumn migration under monochromatic green light (565 nm) produced by light-emitting diodes at various light levels. At intensities of 0.0021 and 0.0075 W/m(2), the birds showed normal activity and were oriented in their seasonally appropriate migratory direction. Under low light of 0.0002 W/m(2) the birds were less active; scatter increased, but they still oriented in their migratory direction. Under a high light level of 0.0150 W/m(2), however, the test birds showed a counterclockwise shift in direction, preferring west-northwest instead of north. This change in behavior may reflect a change in the output of the magnetoreception system, resulting from a disruption of the natural balance between the wavelengths of light.
Wiltschko
W
W
Fachbereich Biologie, Zoologie, J.W. Goethe-Universität Frankfurt, Siesmayerstrasse 70, D-60054 Frankfurt, Germany.
Wiltschko
R
R
Munro
U
U
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001717:Birds / Q000502:physiology*; D008027:Light; D008029:Lighting; D008280:Magnetics; D009949:Orientation / Q000502:physiology*; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D012621:Seasons