Perception of alterations in natural budgerigar (Melopsittacus undulatus) warble: Implications of animal “syntactical capability.”

Abstract

The warble song of male budgerigars (Melopsittacus undulatus) is an extraordinarily complex, multisyllabic, learned vocalization that is produced continuously often for minutes at a time. Previous work has shown that warble elements form acoustic and perceptual categories for budgerigars and these birds can detect ordering changes in artificial sequences of warble elements. Using operant conditioning and a psychophysical paradigm, we examined the sensitivity of budgerigars for detecting different types of insertions (e.g., targets) in a running background of warble up 1000 elements in length. When the inserted targets are warble calls taken directly from the background, budgerigars show a species-specific ability to detect them solely based on sequence violations in the natural ordering of warble elements. Moreover, budgerigars, but not other species, are especially sensitive to temporally reversed warble elements inserted in natural warble sequences, indicating that the acoustic details of warble elements are also perceptually significant to budgerigars besides sequential cues. Although it is still unclear whether budgerigars perceive their warble as a rule-govern sequence or a pattern-based vocalization, the findings here open the door to studies of serial order learning in a natural, non-human communication system. [Work supported by NIH/NIDCD R01DC000198 to R.J.D.]