From the website:

Image library of songbird nuclei—Area X, HVC, and RA—allowing comparisons examining sex differences and effects of various doses of estrogen given to females in posthatch development. Bird Song System is an instructional tool for teaching neurophysiology that requires only a computer.  Bird Song System is available for free, along with student and instructor tutorials.  Module teaches about organizational effect of gonadal steroids on brain development and use of ANOVA and post-hoc tests.