Table 1.

Results of mediation analysis

		a		b		c		c’		CI	df
Variable		Coefficient	P	Coefficient	P	Coefficient	P	Coefficient	P
Song	MeA	4.351	<0.001	5.630	0.017	10.417	0.022	−14.639	0.156	2.389, 45.956	22
	PVN	6.282	0.049	0.666	0.041	10.417	0.022	4.92	0.304	0.691, 12.117	22
Trips	POM	−16.680	0.037	0.093	0.003	−1.741	0.042	0.023	0.973	−3.503, −0.510	11

The effect of morph on singing in response to STI (c path, Fig. 4) was reduced and no longer significant (c’ path) when the ab path including ERα expression in the MeA or the PVN, which were both significant, was considered. Similarly, the effect of morph on provisioning trips was reduced and no longer significant when the ab path including ERα expression in the POM was considered. These results are consistent with the hypothesis that ERα expression in MeA, PVN, and POM fully mediates morph differences in behavior.