Figure 1.

Sound spectrograms of some of the test stimuli used in playback experiments. Normal (N), isolate (I), and savannah sparrow song (S) were presented in the first experiment. Reversed song (R), whistle songs (W), buzz songs (B), and trill songs (T), as well as N and S, were tested in the second experiment. Buzzes have a larger bandwidth and more amplitude modulation than whistles. Trills are repeated series of discrete frequency-modulated (FM) sweeps. Note that the song sparrow song contains short whistles and a trill. (Scale bar represents 1 second.)