Table 1.

Mass of either the testes or oviduct, plasma testosterone (T) concentration, and plasma estradiol (E2) concentration (± S.E.M.) for male and female zebra finches from mixed-sex housing. Subjects were treated with vehicle or Letrozole on a daily basis for three weeks. Subjects were also given subcutaneous implants that were either empty or filled with crystalline E2 for the duration of the study. Abbreviations: CTRL, vehicle plus empty implant; LET, Letrozole plus empty implant; LET+E2, Letrozole plus E2; N, group size. See text for statistical differences among groups. Adapted from Kabelik et al. [35].

	Females			Males
	CTRL	LET	LET+E2	CTRL	LET	LET+E2
N	6	5	3	6	5	6
testes or oviduct mass (g)*	0.073 (0.024)	0.023 (0.006)	0.43 (0.08)	0.048 (0.006)	0.042 (0.005)	0.003 (0.001)
T (ng/ml)*	0.033 (0.006)	0.28 (0.040)	0.016 (0.007)	3.47 (0.67)	3.84 (0.95)	0.023 (0.004)
E2 (ng/ml)*	0.023 (0.003)	0.030 (0.004)	1.82 (0.14)	0.033 (0.005)	0.052 (0.010)	0.99 (0.21)

*Testes mass, p < 0.0001

*Oviduct mass, p < 0.0001

*T level, males vs. females, p < 0.0001

*T level, treatment effect, p < 0.0001; posthoc: LET > CTRL > LET+E2

*T level, sex*treatment, p < 0.0001; posthoc: ♂ LET = ♂ CTRL > ♀ LET > ♀ CTRL = ♂ LET+E2 = ♀ LET+E2

*E2 level, treatment effect, p < 0.0001; posthoc: LET+E2>CTRL=LET

*E2 level, sex*treatment, p = 0.007; posthoc: ♀ LET+E2 > ♂ LET+E2 > ♂ LET ≥ ♂ CTRL ≥ ♀ LET = ♀ CTRL