The correlation between the degree of brain masculinization and song quality in estradiol treated female zebra finches.

Female zebra finches can be induced to develop a male-like song system by being exposed to a steroid as nestlings. After subsequent testosterone treatment they develop song whose quality depends on age and duration of early steroid treatment. This study compares the anatomy of two song nuclei with the birds' song quality. The capacity for song correlates with the volumes of the nucleus hyperstriatum, ventralis, pars caudalis (HVc) and the nucleus robustus archistriatalis (RA) and with the size of RA neurons.