Figure 1: Circadian rhythms of locomotor and feeding activity from an intact pigeon. The pigeon was in an LD cycle for the first 5 days of this record (lights on - up arrow; lights off - down arrow) and in DD (horizontal arrows) for the remainder of the experiment. The records are double plotted to facilitate visual inspection of the data. Locomotor data for days 39-49 were lost due to a data acquisition hardware problem.