Magnetic orientation of snow buntings (Plectrophenax nivalis), a species breeding in the high Arctic: passage migration through temperate-zone areas

Orientation tests were conducted with snow buntings (Plectrophenax nivalis) exposed to artificially manipulated magnetic fields, during both spring and autumn migration. Experiments were run under clear sunset skies and under simulated complete overcast. The birds closely followed experimental shifts of the magnetic fields during both seasons regardless of whether they had access to celestial cues. Clear-sky tests in vertical magnetic fields resulted in a significant bimodal orientation, the directionality of which was almost identical during spring and autumn. When the snow buntings were deprived of celestial directional information and tested in vertical magnetic fields, they failed to show any statistically significant mean directions in either spring or autumn. The results demonstrate that snow buntings possess a magnetic compass and suggest that magnetic cues are of primary importance for their migratory orientation while on passage through temperate-zone areas. However, the axial orientation in vertical magnetic fields under clear skies may indicate an involvement of celestial cues as an auxiliary source of directional information.