Fig. 1. Pictorial representation of the experimental design used to evaluate effects of RU486 treatment in the Gambel's white-crowned sparrow. Spring migrants and wintering birds were held on 16 h:8 h L:D and 8 h:16 h L:D, respectively. (A) Experimental protocol designed to investigate the behavioral responses of birds to RU486 treatment under ad libitum food conditions. Treatment effects were tested by comparing birds one day before and one day after RU486 injections. Controls received vehicle injections. Birds were monitored for differences in locomotor activity (as determined by motion detectors in registration cages) and daily food intake. (B) Experimental protocol designed to investigate the behavioral and metabolic responses of birds to RU486 treatment during a food manipulation trial. On the morning following the second RU486 injection, food in chambers was removed for four hours. Birds in a second chamber continued to experience ad libitum food conditions. Locomotor activity and plasma metabolites were monitored during the trial. After food was replaced, locomotor activity and food intake were measured to determine how RU486 affects recovery. Controls continued to receive vehicle injections.