Fig. 1.

The stimulation setup consisted of three orthogonal Helmholtz coils. The total magnitude of the artificial field was kept similar to the amplitude found in Santiago. Most of the experiments recorded from the left tectum and the right eye was illuminated with LEDs located at 50 cm behind a translucent screen. A 3D magnetic sensor (MS) was located near the pigeon beak. The coils and LEDs were powered by high current 12 V DC batteries. In experiments with awake pigeons the ear bars were not used. The coils left most of the right visual field unobstructed