The Experimental Investigation of Navigation in Homing Pigeons

Abstract

1. A series of field experiments were carried out in 1948, 1949 and 1950 to establish the facts of navigation in homing pigeons and to begin an investigation of the factors involved. 2. A total of 158 pigeons aged 3-4 months were used in twenty-three tests involving a total of 902 sorties, all but 153 being by birds released singly. 3. Three indices of performance were used, giving the degree of uncertainty on release, the accuracy of the initial course and the success in regaining home. 4. It was shown that pigeons are able to fly in one particular direction when released at a series of unknown points at increasing distances north-north-west of the loft. The following of experienced birds or the use of distant landmarks were excluded. 5. Overcast skies had a disorientating effect on these training-line releases. It was shown that if the sun was being used to determine the training direction, it was not by any simple fixed-angle relationship to home. The birds could take large changes of azimuth into account, and at least ignore changes in altitude, without having witnessed the sun's movement. 6. Releases were also carried out in unknown areas at right angles to or in the opposite direction from the training line. Some of the birds flew in the training direction and homed badly. But a good proportion showed a definite orientation in the home direction and returned with fair success. 7. This true navigational ability was shown to vary widely amongst individual pigeons. The proportion of able navigators also varied in different stocks. There is little evidence of a continuous maturation of the faculty with experience and none with age. There are suggestions that it is not connected with a learning process. 9. The established facts require more than a random or systematic search for landmarks, or the use cf atmospheric clues as an explanation. 10. It is shown by experiment that pigeons do not depend on the interpretation of the earth's magnetic field to be able to orientate in the training or in the home direction. 11. Other experiments show that a displacement recording mechanism based on time/acceleration measurements is extremely unlikely. 12. The only positive lead obtained is a definite suggestion that overcast had a disorientating effect on pigeons released off the training line. This requires detailed confirmation. The simplest way in which a pigeon could obtain a rough estimate of its position relative to home by measuring the sun's co-ordinates is considered. 13. Attempts to follow individual pigeons or groups of three by aircraft have so far been unsuccessful. An automatic flight recorder has been used successfully to some extent.