MAGNETIC INFORMATION AFFECTS THE STELLAR ORIENTATION OF YOUNG BIRD MIGRANTS

WHEN young birds leave on their first migration, they are guided by in nate information about their direction of migration. It is generally a ssumed that this direction is represented twice, namely with respect t o celestial rotation and with respect to the Earth's magnetic field(1, 2). The interactions between the two cue systems have been analysed by exposing hand-raised young birds during the premigratory period to cu e-conflict situations, in which celestial rotation and the magnetic fi eld provided different information. Celestial rotation altered the cou rse with respect to the magnetic field(3-7), whereas conflicting magne tic information did not seem to affect the course with respect to the stars(8,9). Celestial information thus seemed to dominate over magneti c information. Here we report that the interaction between the two cue systems is far more complex than this. Celestial rotation alone seems to provide only a tendency to move away from its centre (towards geog raphical south), which is then modified by information from the magnet ic field to establish the distinctive, population-specific migratory d irection.