INTRODUCTION

A major focus in the study of bird song over the past three decades has been on the involvement of learning during development. At a basic level, two models of learning mechanisms have been proposed: instructive and selective (Jerne 1967; Changeux et al. 1984). In an instructive model, environmental stimulation adds information not already present in the behavioral repertoire. When a young bird memorizes a novel song, it is instructed. In contrast, in a selective model, learning consists of the selection of behavior(s) from a pre-existing repertoire as a function of experience. At the time of stimulation, the animal already possesses the potential or ability to perform the behavior. Therefore, the test to distinguish between the two models is to present a novel stimulus and to record whether it is learned.

Research on song learning has been guided largely by an instructive model of learning, embodied in the sensorimotor model first proposed in Konishi's (1965) study of song development in the white-crowned sparrow (Zonotrichia leucophrys). The sensorimotor model includes two stages: a sensory (instructive) phase in which songs are memorized, and a sensorimotor phase in which the bird compares its own song, via auditory feedback, to the memory trace acquired earlier.

One consequence of song learning is the formation of geographic “dialects” in which males at one location sing similar songs that differ from those of the same species at other locations. If vocal plasticity in birds is mediated solely by an instructive mechanism, then song matching dialects arise when males breed in the same area where they acquired their song(s).