OVERCAST TESTS WITH CLOCK-SHIFTED PIGEONS

In order to investigate the pigeon's compass mechanism, a series of ov ercast tests with clock-shifted birds were run at two familiar release sites. While controls were able to assume a correct homeward directio n, the experimental birds' initial orientation cannot be explained eit her on the basis of a time-compensated sun compass or of a time-indepe ndent magnetic compass. Speculative explanations of our paradoxical re sults are attempted.