By Tanya Lewis, Staff Writer | March 20, 2014 03:26pm ET
Everyone knows cuckoos are the freeloaders of the animal kingdom, laying their eggs in other birds' nests. But such slackers may not be total parasites.
A study of great spotted cuckoos and the carrion crows that raise the cuckoos' young finds that young cuckoos secrete a noxious substance that repels predators that come to attack the nest. These results suggest cuckoos and crows have a mutually beneficial relationship.
Researchers were studying carrion crows in Spain when they noticed a strange pattern. When cuckoos were present at a crow's nest, the nest had lower chances of being predated by feral cats and birds of prey. And when threatened, the baby cuckoos released a stinky secretion, which seemed to deter the predators.