The influence of magnetic information on the orientation of the indigo bunting, Passerina cyanea

Abstract

Summary The recent studies of Merkel and Wiltschko have renewed discussion of possible magnetic orientation in migrating birds. Stimulated by their affirmative findings, I examined the importance of geomagnetic information to migratory orientation in the Indigo Bunting ( Passerina cyanea ). Three series of experiments were conducted: 1. Directional preferences of caged buntings were noted in a large planetarium. When the artificial sky was manipulated so that stellar and magnetic north did not coincide, the birds oriented with reference to celestial information. Presented with geomagnetic cues only (stars shut off), the birds' orientation deteriorated to random. 2. Birds tested repeatedly in the presence of a normal geomagnetic field but in a ‘visually cueless’ chamber failed to develop any significant directional preferences. 3. Attempts to classically condition buntings to respond to directional changes (of 1 s duration) in the horizontal component of an artificially induced magnetic field have been unsuccessful. In summary, I have been unable to obtain experimental confirmation of the hypothesis that Indigo Buntings can perceive and use static magnetic fields as directional cues.