Fig. 3. Number of high-frequency chirps (mean ± s.e.m.) produced during playback stimulation as a function of Df in male (A,B) and female (C,D) A. leptorhynchus (A,C) and A. albifrons (B,D). (A) Male A. leptorhynchus (N=11) produced significantly more high-frequency chirps to the –150 Hz Df than to the –5 Hz Df. (B) In a pattern opposite to that seen in A. leptorhynchus, male A. albifrons (N=16) produced significantly more high-frequency chirps to same-sex stimuli (within 20 Hz) than to opposite sex stimuli (±150 Hz). (C) Female A. leptorhynchus (N=9) produced almost no high-frequency chirps, and Df did not affect their production. (D) There was no effect of Df on the number of high-frequency chirps produced by female A. albifrons (N=15), although the trend was similar to the effect of Df seen in males. Data points with different letters differ significantly from each other Tukey's HSD, P<0.05. NS, no significant effect of Df (repeated-measures ANOVA, P>0.05).