Song-syllable perception in song sparrows (Melospiza melodia) and swamp sparrows (Melospiza georgiana): An approach from animal psychophysics

Perception of song syllables by female song sparrows (Melospiza melodia) and swamp sparrows (Melospiza georgiana) was examined using operant conditioning techniques. Similarity matrices among song syllables were constructed from response latencies to detect changes in a repeating background of syllables. Multidimensional scaling (MDS) of these similarity matrices described the perceived relations among the syllable types for each bird. Both species distinguished in a similar way between song- and swamp-sparrow syllables extracted from natural songs. However, when selected features of the syllables were modified, song sparrows and swamp sparrows showed different patterns of perceptual confusion. These results illustrate the utility of MDS techniques for investigating the perception of complex vocal signals, as they demonstrate species differences in the perceptual significance of equivalent physical changes in such complex sounds. The findings also support the notion that swamp sparrows are more selective than song sparrows in the perception of species-specific song syllables.