The roles of the sun and the landscape in pigeon homing

It seems reasonable to assume that pigeons use visual features in the lands cape for orientation when they are homing over familiar terrain. Experiment al evidence to prove or disprove this possibility is, however, difficult to obtain, Here, we link the problem with the observation that deflections of initial orientation caused by clock-shift are often smaller than predicted on a pure sun compass basis. We substantiate the hypothesis that consisten tly reduced deflections and increased angular scatter occur only when pigeo ns are released in familiar areas where a remembered pattern of landscape f eatures can conflict with the position of the sun. Repeated releases of the same individuals under clock-shift, or elimination of non-visual navigatio nal clues (odours), appear to strengthen the conflicting influence of famil iar visual landmarks. Accelerated returns of birds allowed to preview the s urrounding familiar scenery before release also support the conclusion that the visual environment is included in the homing system of pigeons. The la ndscape, however, not only helps home-finding, if it is familiar, but may a lso have a distracting influence that contributes to the great variability of initial orientation patterns.