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The factors affecting the olfaction-based navigational performances of homing pigeons released at relatively long distance (beyond 100 km from home) have in the past been subject to several investigations both in Germany and Italy using observations of vanishing bearing distributions. These studies highlighted the complexity of long-distance navigation in homing pigeons, which remains a poorly investigated aspect. In this tracking study we report how the homing performances of pigeons housed in Arnino (Pisa, Italy) were affected by the presence/absence of a mountain range (the Northern Apennines) interposed between the home and the release site area (release sites: Trans = mountain barrier, Cis = no mountain barrier). We displaced unmanipulated control pigeons, anosmic pigeon, and pigeons transported in purified air to release sites located at a distance ranging between 95 and 246 km from home. There, birds were released without further manipulation. The navigational performances of anosmic pigeons were impaired at both Cis and Trans sites compared to both smelling groups. Both unmanipulated control pigeons and pigeons transported in purified air but allowed to smell environmental air at both the release site and after release displayed unimpaired navigational abilities at the Cis site, but impaired homing success and impaired homeward orientation at the Trans sites. Nevertheless, their homeward component was significantly greater than that of the anosmic birds at both geographical areas. This suggests that the Northern Apennine acts as a geographical barrier affecting the olfactory map accuracy of Arnino pigeons, rather than totally reducing its spatial extent. [ABSTRACT FROM AUTHOR]

The navigational mechanisms of homing pigeons, Columba livia , have been extensively studied and represent a useful model for the navigation of birds and other animals. Pigeons navigate with an olfactory map and sun compass from unfamiliar areas and, in familiar areas, are largely guided by visual landscape cues, following stereotyped and idiosyncratic routes. However, the mechanisms by which they gain familiarity, improve their navigation and transition between navigational strategies during learning are not fully understood. Addressing these outstanding questions in this navigational model will help to improve our understanding of navigational ontogeny. We sought to investigate whether passive exposure to the cues at a site, without release, was sufficient for navigational learning, given that pigeons can determine the home direction before taking off. We exposed pigeons to cues at a novel site before returning them to the site the next day and releasing them alongside controls. We found no differences in the directional distributions, mean vector lengths, virtual vanishing times, efficiency indices or homing efficiency indices between birds that had and had not previously visited the site. We therefore found no evidence to suggest that passive exposure to the cues at a novel site was sufficient to facilitate a detectable improvement in navigational performance. There are three possible explanations for this result: first, a larger sample size would have detected a weak effect of learning; second, passive exposure to a release site is insufficient to generate navigational learning; and third, pigeons learn from passive exposure but do not rely upon this information, showing no difference in performance, despite learning. We discuss these three explanations with reference to previous findings on navigational learning in homing pigeons. We suggest that experiments should continue to examine navigational ontogeny in homing pigeons to help address this major problem for the field of navigation. • The ways navigational learning proceeds in homing pigeons are not fully understood. • We investigated whether exposure at a novel site is sufficient for learning. • We found no evidence that exposure to a novel site improved homing performance. [ABSTRACT FROM AUTHOR]

Several laboratory studies have revealed functional hemispheric lateralization in birds performing visual tasks. However, the role of functional brain asymmetries in spatial behaviour in natural settings is still poorly investigated. We studied monocularly occluded homing pigeons, Columba livia , to investigate potential differences in the hemispheric control of navigational performance. We GPS-tracked monocularly occluded and control binocular homing pigeons during seven group training releases and a final solitary release from each of two sites. The pigeons were then given one last release from each site after a phase shift of the light-dark cycle under binocular conditions, to distinguish compass-based orientation from landmark-based pilotage. Overall, pigeons homing with the left eye/right hemisphere (RH) displayed a greater fidelity to the familiar space previously experienced than pigeons homing with the right eye/left hemisphere (LH). Another difference between the two monocular groups is that LH pigeons were more likely than RH pigeons to fly with other pigeons during the group training releases. The data support the hypothesis that the left eye/right hemisphere plays a more substantial role as pigeons develop fidelity to certain routes to home from familiar release sites, an enhanced fidelity that may be supported by superior memory for familiar landmarks. [ABSTRACT FROM AUTHOR]

The role of environmental olfactory information in pigeon navigation has been extensively studied by analysing vanishing bearing distributions and homing performances of homing pigeons subjected to manipulation of their olfactory perception and/or the olfactory information they were exposed to during transportation and at the release site. However, their behaviour during the homing flight remains undocumented. In this experiment we report the analysis of tracks of birds made anosmic at the release site by washing their olfactory mucosa with zinc sulfate. We thus can assess the role of local odours at the release site as well as the role of environmental odours perceived on the way, far from the release site. We observed that pigeons transported and kept at the release site in purified air and made anosmic at the release site were unable to orient towards home and were impaired at homing. By contrast, pigeons allowed to smell environmental odours during transportation and at the release site, although made anosmic prior to release, displayed unimpaired homeward orientation, but nevertheless showed impaired homing performance. These results are consistent with the view that local odours at the release site are critical for determining the direction of displacement (olfactory map) and suggest that pigeons consult the olfactory map also during their homing flight in order to be able to find their way home. [ABSTRACT FROM AUTHOR]