Initial Orientation of Anosmic Homing Pigeons Based On Information Gathered At Familiar Release Sites Remains Homeward Directed Following Clock-Shift

In addition to their well described map and compass mechanisms, homing pigeons can also rely on information gathered during previous visits to a release site (familiar-site information) to orient home from that location. In the present study, we wished to clarify the nature of the spatial information acquired during visits to a release site. Clock-shifted homing pigeons, rendered anosmic such that they could only rely on familiar-site information to orient homeward, failed to display the typical shift in initial orientation indicative of sun compass use as displayed by controls. This result indicates that familiar-site information can be used not only for recognition of previous visited locations, but also to guide a pigeon's orientation response. However, there was an increase in scatter in the vanishing bearings of clock-shifted pigeons whose initial orientation was based on familiar-site information, suggesting that the solar cues were part of the available familiar-site information. Finally, clock-shifted pigeons who could rely on both their navigational map and familiar-site information for initial orientation behaved in a manner suggesting primary use of their navigational map with additional reference, at least to a limited degree, to familiar-site information.