Cuckoo mafia: Host birds only tolerate parasitic eggs in their nests when they fear retaliation

The brown-headed cowbird is nothing short of a nightmare for its hosts: If they eject the brood parasite’s eggs from the nest, it punishes them by destroying their entire clutch. Researchers have designed a mathematical model for analyzing the interaction between avian brood parasites and their hosts. The model calculations show that birds only accept a brood parasite’s eggs in their nests if they are forced to do so by threat of retaliation on the part of the invader.