Experiments were performed with homing pigeons treated before release with oscillating magnetic fields produced by small Helmholtz coils placed around the neck and on the head of the pigeon or by larger Helmholtz coils surrounding the cage of the birds. In both types of treatment, which both used a single frequency of about 0.14 Hz, the pigeons' initial orientation was strongly affected when the oscillation of the artificial magnetic field was square-shaped, whereas a triangular or sine-shaped variation had no effect.

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