Locomotory Activity of Day-Migrating Finches

Abstract

In a first experiment, six goldfinches (Carduelis carduelis) caught as fledglings were kept separately under identical natural conditions in registration cages. The birds showed locomotory activity only during the daylight cycle. Activity increased twice: once during the autumn and once during the spring-migration period. By correlating the locomotory activity with the length of day there was found a theoretical course of activity, based on the linear correlation of locomotory activity and increasing or decreasing daylength. Subtracting this calculated activity from the real activity shown by the caged birds, one is able to define the migratory restlessness (Zugunruhe) of diurnal migrating birds. During the period in which the birds actually show migratory restlessness, they were held in orientation cages without a view of the sun to determine whether there is a preferred direction. The goldfinches had a statistically significant preferred direction at the time they were in migratory restlessness.