Fig. 12. Towhees tend to produce low sound frequencies in `tow-hee' calls with a small beak gape but produce high sound frequencies with a large beak gape. Plotted are measurements of beak gape and measurements of peak sound frequency obtained from audio frames corresponding with video frames. (A) Calls recorded in Florida (362 frames from 50 calls produced by seven subjects). (B) Calls recorded in Indiana (854 frames from 97 calls produced by 6 subjects). Sound frequencies above the dashed line (3.75 kHz) seem to be attenuated as towhees close their beaks (Fig. 5). Arrows depict directional pressures that are described in the text.