Figure 4 in Insect noise avoidance in the dawn chorus of Neotropical birds

Figure 4. Nonavian noise level at different frequencies up to 9 kHz. Each line displays the average background noise colour-coded for each 5 min time interval from 30 min before until 30 min after sunrise. Black triangles indicate peak frequency of songs from the 27 bird species recorded. Amplitudes of nonavian noise are given as negative values relative to the maximum input of the recording units.