“To answer this question, I knew we were going to need what amounts to facial recognition software for eggs,” says Stoddard. The differences in pattern and color in these host egg types are so subtle that they often can’t be detected by human observation. “You can’t pick up the difference by eye—you really need a computer to analyze them,” she says. So Stoddard teamed up with a computer scientist, Chris Town of the University of Cambridge, and created NaturePatternMatch, software that identifies features on an egg that are likely important to a bird.