For those of you who are interested in the phenomenon of migration, and
who don't have a subscription to Science, the lead author, William W.
Cochran - can be contacted via
Regards, Laurie.
Migrating Songbirds Recalibrate Their Magnetic Compass Daily from
Twilight Cues
William W. Cochran,1* Henrik Mouritsen,2 Martin Wikelski3
Science Vol 304, Issue 5669, 405-408 , 16 April 2004
Night migratory songbirds can use stars, sun, geomagnetic field, and
polarized light for orientation when tested in captivity. We studied
the interaction of magnetic, stellar, and twilight orientation cues in
free-flying songbirds. We exposed Catharus thrushes to eastward-turned
magnetic fields during the twilight period before takeoff and then
followed them for up to 1100 kilometers. Instead of heading north,
experimental birds flew westward. On subsequent nights, the same
individuals migrated northward again. We suggest that birds orient with
a magnetic compass calibrated daily from twilight cues. This could
explain how birds cross the magnetic equator and deal with declination.
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