Developmental and functional aspects of avian vocalizations will be treated. Field and laboratory studies on song development will be compared and the effects of live vs. tape tutoring on the sensitive phase, onset of subsong, time of song crystallization and quality of crystallized song will be discussed. Modes of cultural tradition will be reviewed including vertical, oblique and horizontal traditions, as well as traditions along sexual lines. Field and laboratory studies on the circannual cycles of neurogenesis in the HVC and RA song control centres in the brain will be compared and the results related to studies of vocal development. Evidence for stimulus filtering in vocal ontogeny will be reviewed and evidence for the effects of social interaction overriding ‘innate' preferences to learn conspecific song will be presented. These data will be interpreted in terms of Cody's ‘Character Convergence' hypothesis. The effects of vocalizations on gonadal recrudescence will be reviewed with emphasis on the synergistic vs. complementary roles of song vs. photoperiod discussed. Finally, evidence for the pituitary's circadian sensitivity to song vs. LD-cycle will be presented.