Figure 40.10: The Sun Compass of a Homing Pigeon Requires That the Pigeon Interpret the Sun’s Position in the Sky Based on Knowledge of Time of Day A pigeon trained to fly south to find home was tested in the Northern Hemisphere. Here we see a bird’s eye view of the southern horizon, from east to west, with the sun passing overhead between dawn and dusk. (A) The pigeon with its circadian clock functioning normally. Using time-of-day information from its circadian clock, the bird flies at angle α to the right of the sun in midmorning but at angle β to the left of the sun in midafternoon. (B) The pigeon with its circadian clock entrained so that the clock says the time is midafternoon when the actual time is midmorning. The pigeon flies at angle β to the left of the sun and thus flies east instead of south.