Gene expression profiles from two brain systems that govern singing behavior. A) PCA plot showing the separation of different brain regions on PC1 and PC2. B) PCA plot showing further separation of the brain regions on PC3 and some separation of the treatments on PC4. C). Heatmap of the 132 cDNAs in POA with significant changes across the treatments. The POA heatmap reveals waves of gene activation as starlings transition across the different photoperiodic states. D) Heatmap of the 590 significant cDNAs in HVC. This patterns shows a categorical shift between LD7 and LD21. E) Heatmap of the 194 significant cDNAs in Area X, also showing a categorical shift between LD7 and LD21. F) Heatmap of the 228 significant cDNAs in RA, which shows a mix of expression pattern types. Curly brackets on the left side of C) and D) indicate which groups of cDNAs were selected for GO analysis. Abbreviations: SD - short days for fifty-six days; CXT - castrated for seven long days; LD7 - intact for seven long days; LD21 - long days for twenty-one days; and LD56 - long days for fifty-six days.