The Greater Honeyguide is the Jekyll and Hyde of birds. At least, that’s how Claire Spottiswoode tells it. The zoologist from the University of Cambridge has spent the past eight years studying the species’s dark side in the wooded savannas of southern Africa. Minutes after entering the world, Greater Honeyguide chicks turn murderous, using the barbed ends of their beaks to slay their nest mates. But the victims aren’t the young honeyguide's kin—they’re actually the offspring of the nest’s rightful owners, which now have the unfortunate task of raising a brutal brood parasite. More recently, Spottiswoode has been focused on studying the kinder side of the honeyguide. As adults, the pink-billed birds live up to their name, leading local hunters to wild beehives stashed in the cavities of baobabs and other tall trees. The men then scale the trunks, smash the hives, and make off with the sticky riches, leaving the wax and the calorie-rich larvae within for...