INTRODUCTION Konishi, while a student with Marler, showed that birds must be able to hear themselves sing to develop song normally. Fernando Nottebohm, also This special issue of the Journal of Neurobiology while a student with Marler, showed that the peis devoted to a consideration of the avian song ripheral control of song production is lateralized. control system. In the 20 years that have passed Nottebohm and his colleagues subsequently idensince Nottebohm et al. (1976) first identified foretified neural circuits in the avian forebrain that brain circuits that control song in birds, the song control song behavior. This important discovery system has emerged as a leading model in behavpaved the way for many investigators who have ioral neuroscience. To mark the beginning of the subsequently contributed to our understanding of third decade of study of this model, we invited song behavior and its neural control. several leading investigators to contribute to this The birdsong system offers several advantages volume. We set two goals for the authors: to reas a model for identifying neural mechanisms that view progress in their area of study and, more underlie biologically relevant behavior: important, to identify critical directions for future research. 1. Song is a learned behavior that is controlled The modern study of birdsong began with the by discrete neural circuits. work of William Thorpe (1958, 1961) . He 2. There are distinct phases in the development showed that chaffinches (Fringilla coelebs ) colof song, with well-defined sensitive periods. lected as nestlings and reared in the laboratory in One can relate the ontogeny of song behavior isolation from conspecific adult males produced to the development of the underlying neural very abnormal songs. If these young birds were circuits. exposed to tape recordings of wild chaffinch 3. Song is the product of stereotyped motor prosongs, however, they eventually produced normal grams, with hierarchical organization of the songs that matched those heard on the recordings. premotor and motor nuclei. These studies demonstrated for the first time that 4. Song behavior and the associated neural ciryoung birds must learn the song of their species by cuits are sexually dimorphic in most species. listening to adult conspecifics. Thorpe’s student 5. Gonadal steroid hormones have pronounced Peter Marler greatly expanded upon this early effects on the development and adult function work. Marler and his colleagues demonstrated the of the song control circuits, as well as on song existence of local geographic song ‘‘dialects,’’ behavior. that song learning is characterized by early sensi6. There is extensive plasticity of the adult song tive periods, and that birds have innate predisposisystem, including ongoing neurogenesis and tions to learn the song of their species. Masakazu seasonal changes in morphology. 7. There is pronounced species diversity in different aspects of song behavior, including the Correspondence to: E. A. Brenowitz