ADVANCES IN STUDIES OF AVIAN SOUND COMMUNICATION

Ground-breaking advances in the study of animal sound communication per se, and avian vocal behavior in particular, awaited instrumentation that enabled capture of sound signals for objective description and analyses. Once these technological advances became generally available, a groundswell of activity in vocal studies, bioacoustics, provided the ''raw material'' for hypothesis testing pertaining to various biological and evolutionary principles. All aspects of this field cannot be covered in one review. Thus, themes developed herein deal primarily with questions of vocal acquisition such as factors affecting song learning, the sensitive phase and stimulus filtering hypotheses pertaining to the learning process, the effect of vocal behavior on population dynamics, the effect of hormones on the song learning process and production, photoperiod and song as they are related to gonadal recrudescence, advances in the neurophysiological control of song acquisition and production, and the incidence of female song and function across taxa.