HOME-RELATED AND HOME-INDEPENDENT ORIENTATION OF DISPLACED PIGEONS WITH AND WITHOUT OLFACTORY ACCESS TO ENVIRONMENTAL AIR

Using a standardized procedure, homing pigeons, Columba livia, hitherto inexperienced in homing were released 30 km north, south, east and west from home, in this sequence. Half of the birds (FX) were prevented from smelling natural odours by filtration of the air they breathed before release and nasal anaesthesia with xylocain upon release. The other half (NN) could smell natural air at the release site. Sixty releases (18 each from north and south, 12 each from east and west) were conducted in the course of 3 years. Initial orientation patterns were site-specifically different but remarkably similar in NN and FX. A general preference for northwesterly directions was common to both groups. An additional preference for the direction towards home, however, was observed only in NN birds. These findings suggest that all initial orientation of FX, and a great deal of NN, is home-independent orientation. Fluctuations from year to year as well as between days were largely synchronized in NN and FX, indicating that the temporal variability of the pigeons' homing behaviour is also, at least to a considerable degree, independent of the navigation process. Owing to their composite origin, which in part probably has little or nothing to do with the home-finding mechanism, initial bearings of pigeons need to be evaluated and interpreted with appropriate care. © 1993 The Association for the Study of Animal Behaviour. All rights reserved.