Fig. 1. Illustrations of our field (A) and laboratory (B) sound-localization experiments. In the field (A; Experiment I), flight error (FE) was calculated for each trial as the mean angle subtending the `distance' between each perch location, and the axis between the starting perch and the playback speaker. Perch error (PE) was calculated as the angle subtending the `distance' between each perch location. PE describes how perches are distributed in Florida scrub habitat and we use FE (PE/2) as our best estimate for how towhees resolve azimuth the field. In the laboratory (B; Experiment II), we employed a two-alternative forced-choice (2AFC) task in which subjects were required to discriminate between two horizontally apposed speaker positions and fly to perches associated with each speaker. To gauge performance as a function of speaker separation angle, we calculated the percentage of trials in which subjects were able to fly to the perch associated with the speaker that played the sound stimulus.