Navigation by homing pigeons

Abstract

Pigeons are able to home from a distant unfamiliar site, even if, during transportation to this site, they were prevented from gathering potentially useful information on spatial configurations of the external world as well as on their own movements. Hence they can deduce information on their current position in relation to home from local clues in an unfamiliar area which may be hundreds of kilometres away from any experienced location. Most likely the birds have analogues of a map and a compass which are used in a process consisting of two steps. For the second step, a fairly well known «sun-azimuth compass» is used; under overcast skies, it may be replaced by a (less well understood) «magnetic compass». Attempts to explain the «map» component, i.e., the mechanism of site localization, on the basis of astronomical or magnetic clues, have been unsuccessful. It has been found, however, that olfactory signals are basically involved. Homing of pigeons from unfamiliar distant sites requires (a) an intact olfactory receptor system and (b) access to natural environmental air at the current position. Before displacement, at the home site, the birds must have experienced natural wind conditions. During their long-term stay at home, the pigeons presumably associate varying ambient odours with concurrently varying directions of the wind. The mechanism of olfactory navigation is unknown. Pertinent hypotheses, e.g. assumptions on an «olfactory gradient map», are still at a quite speculative stage.