Female cuckoos are renowned for their ability to dupe other birds into rearing their young - but new research shows they begin practising their confidence trickery early. Nick Davis, Rebecca Kilner and David Noble at the University of Cambridge have shown that, having ousted their fellow nest-mates, cuckoo chicks use vocal trickery to persuade their foster parents to feed one mouth as much as they feed four.
In tests a blackbird chick substituted for the host's brood secured only one chick's share of food. When accompanied by the recorded call of a cuckoo chick, however, it was given enough food to feed a whole brood. By mimicking a brood, the "si-si-si" call of the cuckoo ensures the fast delivery of plenty of food by parents even when there is only one mouth to feed.