The initial orientation of homing pigeons subjected to various magnetic disturbances prior to releases was studied. Sine wave oscillations of the magnetic field had no effect at low frequencies, whereas there was a significant and increasing effect at frequencies above 0.42 Hz. Oscillations of either the vertical or horizontal component of the earth's magnetic field were found to have an effect on initial orientation. Keeping the pigeons in a near zero magnetic field or in a natural magnetic field from which either the vertical or horizontal component had been removed also resulted in errors of initial orientation. No significant differences, however, were found in homing performance.