Further Analysis of the Magnetic Compass of Migratory Birds

Abstract

The orientation behavior of migratory European Robins (Erithacus rubecula) during Zugunruhe was used for a further analysis of the characteristics of the birds’ magnetic compass. Tests with Robins adapted to field intensities outside the normal functional range of the magnetic compass show that the process of adaptation to fields outside this range is neither a shifting nor a simple enlargement of the functional range. Tests in several 1-Hz alternating magnetic fields with rectangular and sine-shaped impulses indicate that a certain constant portion of the impulse is necessary to enable the birds to use it for orientation.