Avian maternal hormones are thought to influence reproductive processes in an adaptive manner. Corticosterone (CORT)¹²³ , the principle avian stress hormone, has been shown to be transferred from maternal plasma to the yolk via passive diffusion⁴⁵ . Little is known about the role of CORT in offspring sex determination, however, recent studies, including those that involve experimental manipulation of maternal plasma CORT levels, have implicated the hormone in the mediation of avian offspring sex ratios⁶⁷⁸⁹ . The Australian native Gouldian Finch (Erythrura gouldiae) exhibits distinct head-colour morphs, and females paired with a male of a different head colour have previously been shown to exhibit higher circulating levels of CORT, produce more male offspring and incur higher female offspring mortality¹⁰¹¹¹² . Captive bred E. gouldiae eggs from both matched head colour pairs and mismatched head colour pairs, from two breeding seasons, were analysed to determine whole yolk CORT levels. Contrary to our hypothesis, we found that mismatched pairs, whose maternal circulating CORT levels should be high, produced eggs with yolk CORT levels significantly lower than eggs produced by matched head colour pairs. We also found an egg order effect, with first laid eggs having significantly lower levels of yolk CORT than second laid eggs. As variation in yolk CORT levels was also observed between breeding seasons and clutch sizes the adaptive significance of yolk CORT in this species is discussed.