Behavioral Ecology of Vocal Diversity

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9406217 Bradbury Abstract A major focus of research on vocal communication concerns why and how complex repertoires evolve in some organisms and not in others. Complex vocal repertoires are found in humans (e.g. speech), some other primates, cetaceans, many songbirds, and parrots. Comparative work over the last decades has shown that complex repertoires are used in recognition of individuals and associations, sharing of environmental information, declaring of intentions, and competition for mates (sexual selection). Sexual selection, alone or in combination with individual recognition, seems to account for many of the complex repertoires in songbirds. Nonhuman primates declare subtle variations in intention and have some simple environmental meanings. Cetaceans remain difficult to study, but there is now evidence of both sexually selected repertoires and social association signatures. Although both captive and wild parrots are known to develop complex vocal repertoires and continue to learn new signals as adults, nearly nothing is known about how their complex repertoires are used in the wild. Dr. Jack Bradbury and his students have located a study site in Costa Rica that hosts four species of parrots, has an open forest making direct observations feasible, provides an extensive road system for following the birds, and has sufficient control of poaching that the birds can be approached closely without perturbation. Birds will be outfitted with newly designed radio transmitters and followed intensively. All vocalizations will be recorded and correlated with social composition of groups, environmental contexts, and behaviors. Functions can be verified by playback of natural and modified calls to wild birds. Parrots are extremely responsive to such playbacks. Dr. Bradbury thus hopes to clarify the role of complex vocal communication in a group of animals that, although critical to the general understanding of vocal commu nication processes, has largely remained a mystery. The results will provide a basis for subsequent lab studies on brain-behavior relationships and allow contrasts with other avian and mammalian groups. Furthermore, the extensive ecological data to be collected in this study will be useful to Costa Rican conservation biologists.