Fig. 1.

Timelines for the behavioral groups used in this study. (A) Experimental design for time-course analysis of FoxP1 and FoxP2 behavioral regulation. On the day of the experiment, female birds remained alone in sound attenuation chambers for 2 h (green bar). NS males were discouraged from singing by the experimenter sitting nearby for 2 h (black bar). UD males sang alone in the isolation chamber for variable periods of time (red bars). Arrows indicate the time points at which birds were killed. (B) Experimental design for song variability analysis. Songs sung after the 2 h time point were analyzed for song variability. Birds were not killed in this experiment.