Fig. 2.

Signal plasticity in entrainment experiments. a Duty cycle, chirp duration, chirp rate and time difference between signal onset and chirp onset (Δt) of a male entrained to a periodic conspecific signal gradually increasing in rate (bottom trace). Stable 1:1 phase-locked entrainment occurred up to signal periods of 1.39 s (vertical dotted line). b Chirp duration during entrainment (same as in a) as a function of Δt. Red squares duration of chirps produced during stable 1:1 synchrony, open symbols chirps generated after synchrony was lost. c Relationship between the average duration of leader chirps during synchronous entrainment and average duration of follower chirps (pacer period 2.0 s; 16 song bouts, 11 males). Slope of the regression line is 0.79 and correlation coefficient 0.606. Dashed red line indicates the absence of chirp plasticity. d Average duration of solo chirps, leader and follower chirps during synchronous entrainment (pacer period 2.0 s). Follower chirps were significantly shorter than leader or solo chirps (P < 0.001, paired t test, N = 11 males)