A field study of seasonal neuronal incorporation into the song control system of a songbird that lacks adult song learning

Adult songbirds can incorporate new neurons into HVc, a telencephalic song control nucleus. Neuronal incorporation into HVc is greater in the fall tha n in the spring in adult canaries (open-ended song learners) and is tempora lly related to seasonal song modification. We used the western song sparrow , a species that does not modify its adult song, to test the hypothesis tha t neuronal incorporation into adult HVc is not seasonally variable in age-l imited song learners. Wild song sparrows were captured during the fall and the spring, implanted with osmotic pumps containing [H-3]thymidine, release d onto their territories, and recaptured after 30 days, The density, propor tion, and number of new HVc neurons were all significantly greater in the f all than in the spring. There was also a seasonal change in the incorporati on of new neurons into the adjacent neostriatum that was less pronounced th an the change in HVc. This is the first study of neuronal recruitment into the song control system of freely ranging wild songbirds. These results ind icate that seasonal changes in HVc neuronal incorporation are not restricte d to open-ended song learners. The functional significance of neuronal recr uitment into HVc therefore remains elusive, (C) 1999 John Wiley & Sons. Inc . J Neurobiol 40: 316-326, 1999.