Figure 3.

VIP mRNA expression in the anterior hypothalamus predicts individual variation in song rate (number of territorial songs exhibited during 10 min simulated territorial intrusions) of male (a–d; n = 24) and female (e–h; n = 13) white-throated sparrows. (a,e) Zero-order correlations showing the relationship between song rate and VIP expression in the anterior hypothalamus without correcting for other potential sources of variation in behaviour. VIP expression is plotted as the grey value of the region, corrected for background and averaged across measurements within individual. Partial correlations, shown in the shaded area, depict the relationship between song number and (b,f) VIP mRNA expression, (c,g) morph, and plasma (d) testosterone or (h) oestradiol levels when controlling for the effects of all other variables on behaviour. Multivariate models also included year, Julian day and in situ hybridization run as covariates. Filled circles denote tan-striped birds; open circles denote white-striped birds.