Perception of sequential structure in budgerigar (Melopsittacus undulatus) warble song

Whether the sequential structure of bird song has perceptual significance has long been an interest of animal behaviorists. The long, rambling warble song of male budgerigars is acoustically complex and composed of a number of distinct elements uttered in streams lasting several minutes, usually accompanied by various courtship behaviors, such as head bobbing and beak touching. Recent work has shown that warble song may have a sequential structure, or patterned repetition of elements. This raises questions as to whether budgerigars can detect changes in natural warble streams and to what extent these capabilities are specific to conspecific song. Here, this study examined the perception of long bouts of warble song from male budgerigars. Using operant conditioning and a psychophysical procedure, the study probed the limits of the birds' ability to detect various changes in new and familiar sequences of warble elements. The study shows that budgerigars can detect sequence changes in short unfamiliar sequences of warble and in much longer segments of familiar warble sequences.