Perception of vocal signals by budgerigars (Melopsittacus undulatus).

Budgerigars were trained with operant techniques to discriminate examples of species-specific contact calls. Results show that these birds are capable of learning and remembering for long periods of time both species-specific vocalizations and other complex acoustic signals. While both temporal and spectral cues are important in the discrimination of species-specific calls by the budgerigar, spectral cues occurring in the region of 2 to 4 kHz appear to be critical. These findings are consistent with what is known about spectral resolving power in the budgerigar from critical band, critical ratio, and psychophysical tuning curve experiments. Differences between budgerigars and humans in the filtering properties of the peripheral auditory system may account for species differences in the perception of complex bird calls. In further tests for perceptual categories, multidimensional scaling procedures confirm that contact calls sound different to budgerigars than they do to humans. In addition to providing more evidence for special tuning in the spectral region of 2-4 kHz, these experiments also support the notion of a generalized, flexible, and highly sophisticated perceptual learning system in the budgerigar for the processing of vocal signals.