Fig. 6

Seasonal analysis of song control areas. Androgen receptor mRNA expression (a). HVC: proper name, lMAN: lateral nucleus magnocellularis of the anterior forebrain. Green (HVC) and purple dots (lMAN) indicate mean estimates ± 95% CI, grey dots indicate individual data points. The volume (b) of the HVC was higher during breeding (N = 5) compared to the molt stage (N = 3, p = 0.04), but did not differ to nonbreeding (N = 6). Androgen receptor mRNA expression (c) in lMAN did not differ across seasons. There was a significant interaction effect between brain nuclei and seasons (p = 0.01), with androgen receptor expression in HVC being lower during molt compared to breeding and nonbreeding and to lMAN (breeding: N = 5, molt: N = 5, nonbreeding: N = 6). Males sung in response to the STI during breeding and nonbreeding, but not during molt