Geomagnetic information modulates nocturnal migratory restlessness but not fueling in a long distance migratory songbird

Geomagnetic cues have been shown to influence migratory orientation and migratory fuelling in night-migratory songbird species. Here, we used captive-bred northern wheatears Oenanthe oenanthe from the southern Norwegian population to show that other aspects of the birds’ migratory program can be influenced by magnetic cues as well. We observed that the amount of migratory restlessness increased strongly with progression of the migratory season when the birds were kept constantly in the magnetic field of northern Germany, but the amount of migratory restlessness decreased when the magnetic field changed along the birds’ natural flyway are simulated. Thus, the Earth's magnetic field can also act as a ‘signpost’ cue for fine-tuning the spatio-temporal course of migration.