(A) Volcano plot of differential expression of genes in chest feathers between ornamented (OR) males (black feathers) and control unornamented (UN) males (cream feathers), with significantly overexpressed genes (adjusted P < 0.05) plotted in red. Genes labeled in bold black are part of the melanogenesis pathway, and BCO2 is highlighted in orange for ease of viewing. (B) Total carotenoid concentration in red-backed fairywren (Malurus melanocephalus) back feathers, red-backed fairywren chest feathers, and white-shouldered fairywren (M. alboscapulatus) chest feathers. The color of the points represents the color of those feathers (red, cream, and black). Note RBFW chest feathers were sampled from both ornamented (black) and unornamented (cream) males. (C) A zoom-in of figure 4B to see differences in black and cream RBFW chest feathers. There were no carotenoids detected in unornamented (cream) RBFW chest or WSFW chest feathers and were therefore coded as “0” for these plots.