Sex differences in yolk hormones depend on maternal social status in Leghorn chickens ( Gallus gallus domesticus )

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Abstract
Maternal hormones are known to be present in avian eggs and can have beneficial effects on chick development. Recently, differences in avian yolk steroid concentrations between the sexes have been demonstrated, and in this context steroids have been proposed to be part of the avian sex–determining mechanism. In our study, we show that it is very unlikely that androgen concentrations alone are the decisive part of the sex–determining mechanism. We found that sex–specific differences in the yolk hormones strongly depend on the social rank of the mother. First, dominant females, but not subdominant females, allocated significantly more testosterone to male eggs than to female eggs. Second, subordinate females increased the testosterone concentrations of female eggs.