This story appears in the January 2018 issue of National Geographic magazine. For the care and feeding of its offspring, the common cuckoo outsources. When she’s ready to lay an egg, a female Cuculus ...

SPOILER ALERT: This article contains minor spoilers for “Cuckoo,” now playing in theaters. Roughly 40% of cuckoo bird species are “brood parasites.” Instead of building its own nest, the cuckoo ...