Vocal learning is the ability to learn vocalizations through imitation, and is a rare trait shared by only a few lineages of mammals and three groups of birds. Songbirds more than any other animal model have been indispensable in elucidating the behavioral and neural mechanisms of vocal learning, and they share many key features with human speech cir-cuitry and development. The most highly studied songbird species is the zebra finch (Tae-niopygia guttata), whose song circuitry has been investigated through the many disciplines of genomics, neuroanatomy, neurophysiology, neuroendocinology, behavior, learning, and more. The brain circuitry that drives song learning and production, called the song system, is highly specialized functionally and molecularly, and strikingly sexually dimorphic. This dissertation aims to deepen our understanding of vocal learning and sexual disserentiation in the brain through the detailed molecular lens of transcriptomics.