Some animals produce more offspring than others do. Hormones like prolactin and corticosterone can exercise a crucial influence on the behaviour of birds in the breeding season and therefore on their reproductive success. Scientists from the Max Planck Institute for Ornithology in Radolfzell and their colleagues at the universities of Princeton and Edinburgh have now demonstrated that hormone levels not only play a key role during the breeding season, but already dictate, long in advance, how many eggs a breeding pair will lay, when they will lay them and how often. An animal’s hormonal constitution is thus of major significance for its reproductive success, and is possibly an important driving force of evolution. (Proceedings of the Royal Society B, January 19, 2011)
more in reproduction; it controls the number of eggs per