12 March 2010
Vol 327, Issue 5971

About The Cover

Cover image expansion

COVER Substances deposited by a mother bird into her eggs influence how intensely her offspring beg for food after hatching. In canaries, these substances are effectively a prenatal signal of parental generosity. In contrast to the common assumption, they function primarily to serve the evolutionary interests of the offspring rather than the mother. See page 1373. Photo: Fernando Trabanco