DISSERTATION RESEARCH: The Adaptive Benefits to Vocal Mimicry in a Tropical Mixed-Species Flocking Bird

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

The adaptive benefits to vocal mimicry in a tropical mixed-species flocking bird. Avian vocal mimicry has sparked both a great amount of interest and an equal amount of frustration, as researchers have often been unable to demonstrate the adaptive benefits of this behavior. While it is tempting to think that mimicry of other species influences the behavior of these species to benefit the caller, this has rarely been shown (but see Chu, Behaviour, 2001). In the course of Goodale's dissertation work he has documented mimicry by the Greater Racket-tailed Drongo (Dicrurus paradiseus), a participant in mixed-species flocks of rainforest in Sri Lanka. Drongos have been observed to mimic in two contexts: when solitary they mimic the non-alarm vocalizations of other flocking species, and during mobbing they mimic the other species' alarm calls. In this study, Goodale will test the hypothesis that mimicry functions to attract other species, considering the alternate hypotheses that mimicry is a way of increasing a sexually selected repertoire or a non-adaptive by-product of vocal learning. To do this, he will a) track and tape record drongos inside and outside of flocks, b) elicit responses from drongos with models of perched Accipiter hawks, and c) conduct playback trials measuring the response of heterospecifics to drongo mimicked and non-mimicked vocalizations. The study can serve as a foundation to investigate the cognitive processes involved in this highly context-dependent behavior. It is also a fitting conclusion to a dissertation investigating inter-specific communication in mixed-species flocks.