For the John Templeton Foundation, I wrote about the intricate and deceptive world of bird nest parasitism.
In Greek mythology, Zeus woos a reluctant Hera by transforming himself into a cuckoo and appearing out of a storm as a battered and forlorn creature in need of shelter. She takes the bird in and he thus consummates the marriage that will populate Olympus with a wealth of secondary deities. In nature, the cuckoo often takes a more direct and duplicitous approach to reproductive success. Several dozen cuckoo species are what are called obligate brood parasites — they don’t build their own nests or raise their own chicks, instead laying their eggs in other birds’ nests to be cared for by unwitting foster parents.
Obligate brood parasitism fascinates us for its highly visible metaphors of deception, reproductive trickery (it’s where we get the word cuckold), and bullying. It’s also one of the few cases of parasitism where the parasite is generally bigger than the host. In biology, brood parasites and their hosts present a classic evolutionary arms race, where hosts improve their ability to recognize and evict alien eggs and chicks — or better yet, to keep them from arriving in their nests in the first place. The parasites, meanwhile, are pressured to become more undetectable, unavoidable, or both.