A. Oscillogram showing the structure of the calling songs of A. walkeri. Calling bouts are boxed by red brackets, and echemes are underlined with green bars. The oscillogram shows the varying lengths of the calling bouts, echemes, and echeme intervals. B. Time expanded detail of the first minute and five seconds of A, showing echemes underlined with green bars and echeme intervals underlined with blue bars. The time scale for both oscillograms is minutes:seconds.