SOCIAL AND ACOUSTIC DETERMINANTS OF VOCAL LEARNING

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The aim of the proposed research is to define the roles of imitation and non-vocal social interaction in vocal learning. The subjects are songbirds, which employ a system of complex vocal signals and are among the few animals that exhibit vocal learning. Studies of avian vocal development have made major contributions to our understanding of the perceptual, endocrinological, and neuroanatomical bases of learning in higher vertebrates. The classic account of song learning, which provides the foundation for all this research, emphasizes the imitation of acoustic models as the primary means by which birds learn their songs. More recently, social interaction has been shown to exert major effects on the learning process. These two bodies of research have yet to be integrated into an updated account of vocal development that delineates the respective contributions of social and acoustic influences. The construction of such an account is the broad objective of the proposed research. Three experiments are proposed. Experiment 1 aims to determine what social interaction can contribute to vocal development in the absence of vocal input from a conspecific. Young starlings, Sturnus vulgaris, will be raised with devocalized companions and their songs compared with songs developed by birds reared in previous experiments either in isolation or with a wild-caught singing adult. Experiment 2 aims to identify specific aspects of the social environment that contribute to vocal learning. The behavioral interactions of young birds and their tutors will be observed, and multivariate techniques will be employed to test whether the behavioral measures can predict features of the young birds' songs--i.e., the extent to which they develop species-typical repertoires and syntax. Experiment 3 aims to develop a means of assessing the functional effectiveness of songs acquired under differing conditions of social and acoustic stimulation. This will be accomplished in two ways: (a) Songs recorded from starlings reared under differing conditions of social and acoustic stimulation will be played to estrogen-primed females. If the females exhibit precopulatory displays, as have been elicited in other species in response to playbacks, the number and intensity of the displays can be used as an indication of a song's effectiveness in mate attraction. (b) Starlings will be trained to discriminate between conspecific and heterospecific songs, using an operant procedure. They will then be presented with songs recorded from birds reared under varying experimental conditions. The subjects' categorization of a song will give an indication of its effectiveness in providing a basis for species recognition.