Honeyguides are those African birds that lead people to beehives, in exchange for some of the honeycomb. They parasitize other birds' nests, like cuckoos do. But honeyguides victimize birds who nest in tunnels, so it isn't just a matter of heaving the rightful chick over the side. The honeyguide chick uses a specially barbed beak to savage the other chick to death, and then take its place in its parents' feedings. A macabre arrangement, but that's nature.