For more than 100 years, it was widely assumed that the majority of female birds were sexually monogamous. Charles Darwin himself seems to have started that little rumor. In 1871’s The Descent of Man, he is quite explicit: “The female, though comparatively passive, generally exerts some choice and accepts one male in preference to others.” Darwin was equally clear about the behavior of male birds: they were, like human males, often promiscuous.
Darwin’s ideas were so influential that for the ensuing century, the notion of female fidelity remained unchallenged. My 2008 book, The Wisdom of Birds, out in paperback this month, tells the story of how ornithologists eventually overcame Darwin’s assumption, along with other lessons we’ve learned from studying birds.
It’s likely Darwin knew it wasn’t true. He kept pigeons, and it was well known among pigeon fanciers that the birds engaged in extrapair copulation. Darwin also knew about a ...
