Meet the Cuckoo Mafia

Are you intimidated by this bird? Would you be if it destroyed all your unborn children? Some species of cuckoo and other birds are "brood parasites." This means that instead of raising their own young, they sneak their eggs into other birds' nests and let the adoptive parents do all the work. If you watch these parents taking care of hulking nestlings that are clearly a different species from their own young (and sometimes bully their adoptive siblings out of the nest), it's hard not to see the parents as suckers. But there's evidence for another possibility: that adoptive parents accept baby cuckoos into their nests because they fear violent retaliation if they don't. The "mafia hypothesis" is based on scientists' observations that great spotted cuckoos (above) and brown-headed cowbirds (another brood parasite) can retaliate against birds that oust their eggs. If a host parent tosses a cuckoo or cowbird ...