Pigeon homing: Evidence against reliance on magnetic information picked up en route to release sites

The present study aims to ascertain the nature of the disturbances in initial orientation that have repeatedly been reported in pigeons after transportation to a release site in an altered magnetic field or in the dark. To test whether this effect is caused by an interference in the navigational mechanism or is attributable to an emotional component of homing behaviour, we have recorded the homing behaviour of pigeons injected with the tranquillizer promazine. Birds transported in an oscillating magnetic field or in light-proof containers displayed the expected decrease in homeward directedness, whereas those that had also been injected with promazine oriented like untreated controls. These results show that pigeons do not rely on magnetic information picked up en route to orientate homewards. Magnetic treatments and light deprivation during transportation only appear to affect birds' emotional state, and, as a result, their initial orientation.