Birds sing from the heart. While other four-limbed animals like mammals and reptiles make sounds with voiceboxes in their throats, birds’ chirps originate in a unique vocal organ called the syrinx, located in their chests. No other animals have a syrinx, and scientists aren’t sure how or when it evolved. In a new study in the Proceedings of the National Academy of Science, an interdisciplinary team of developmental biologists, evolutionary morphologists, and physiologists examined the windpipes of birds, crocodiles, salamanders, mice, and cats to learn more about how syrinxes evolved. Their findings seem to confirm: the syrinx is an evolutionary odd duck. But it might have arisen from a reinforcement at the bottom of the windpipe that we still see in many other animals.