Mother birds leave chemical "messages" in their eggs that shape the behaviour of their chicks, research showed.

Nestlings respond to the signals by adjusting the way they beg for food, scientists found.

If chicks get a message that they will be reared by generous parents, they beg more vigorously after hatching. Those destined to be offered less food are not so demanding.

Responding to the messages helps chicks to thrive because they avoid either begging too little or wasting energy on unrewarded begging.

The Cambridge University researchers made the discovery in a study of canaries which involved switching eggs between nests. Study leader Rebecca Kilner said: "We've known for about 20 years that maternal substances in the egg can influence how chicks develop, but the common assumption is that they are a means by which mothers manipulate their offspring in a way that suits the mother more than the chick.

"What we've shown is the reverse: These substances are actually there to suit the chick. If we muck up the message in the egg experimentally, it is the chick that is penalised directly rather than the mother."

The research, which was funded by the National Environment Research Council, is published in the journal Science.