Magnetic compass orientation of European robins under 565 nm green light

European robins tested under monochromatic green light with a peak waveleng th of 565 nm at an intensity of 2.1 mW m(-2) in the local geomagnetic field preferred their migratory direction, heading southward in autumn and north ward in spring. Inverting of the vertical component of the magnetic field c aused the robins to reverse their headings, indicating that the birds used a magnetic inclination compass to locate their migratory direction. The beh avior recorded under green light at an intensity of 2.1 MW m-2 is thus not different from that previously recorded under "white" light; it represents normal migratory orientation.