Penguin chicks benefit from elevated yolk androgen levels under sibling competition.
Crested penguins (genus Eudyptes) have a peculiar hatching pattern, with the first-laid egg (A-egg) hatching after the second-laid egg (B-egg) and chicks from A-eggs typically having a much lower survival probability.Maternal yolk androgens have been suggested to contribute to the competitive superiority of the B-chick in southern rockhopper pengui