Do American and Italian pigeons rely on different homing mechanisms?

Abstract

In an attempt to explain the discrepancy between the results obtained by American and Italian investigators with reference to the role of olfaction in pigeon navigation, 5 series of homing experiments, most of which had already been performed on Italian pigeons, were conducted with Ithaca birds. 1. Application of an odorant (α-pinene) to the birds' beaks and nostrils did not produce consistent differences in initial orientation. The experimental birds were somewhat slower in homing. 2. Elimination of olfactory information during the outward journey did not result in different initial orientation. However, the experimental birds had poorer homing performances. 3. The initial orientation was significantly influenced by one out of 3 sorts of outward journey detours; the positive results from the effective detour could be repeated. 4. Pigeons made anosmatic by inserting plastic tubes in their nostrils were tested from familiar and unfamiliar release sites. At the familiar sites, the control bearings were randomly distributed and not homeward oriented; the experimentals, which were non-random in one site but random in the other, always were homeward oriented. At the unfamiliar site, all the groups were non-randomly oriented. The control birds were homeward directed; the clustering of the experimental bearings around the home direction was not significant or at the boundaries of the significance. Homing performances were very different, the controls performing normally, the experimentals being mostly lost. 5. Pigeons subjected to unilateral sectioning of the olfactory nerve and to plugging of one nostril — the ipsilateral in the control and the contralateral in the experimental birds — were tested from two unfamiliar sites. The orientation of the two treatments was nearly identical at both sites. At one site there was a major difference in homing performance, the controls returning well and the experimentals very poorly; at the other site there was no significant difference in homing performance.