Further Investigations of the Effect of “Flight During Clock Shift” on Pigeon Orientation

Abstract

Keeton and Alexander have shown that use of the sun compass by homing pigeons can be altered by giving the birds exercise flights at the home loft while they are undergoing 6-h phase shifting; such birds, when tested at a release site, usually choose bearings deflected much less than 90° from those of control birds. As a follow-up to these experiments, we used exercise in flight cages (1.8 × 7.3 × 1.8 m) to try to determine how much flight is necessary to produce such a result. All 16 of our cage-exercised groups had mean departure bearings intermediate between those of control birds and those of a group of normal clock-shifted birds. This is strong evidence that the very restricted flight in the cages was sufficient to alter the pigeons’ response to being clock-shifted. Less definitive, but nonetheless strongly suggestive, evidence indicates that exercise in cages aligned E-W was more effective than exercise in cages aligned N-S, probably because of the differing relationships to the home direction. In a second series of experiments, pigeons given repeated unidirectional training flights while living under clock-shifted conditions were found to choose bearings only slightly deflected from those of controls. When such birds were put back under a normal photoperiod and retested, their bearings were substantially deflected, suggesting that they had previously recalibrated their sun compass, though alteration of cue utilization may also have been involved.