When you hear that “tweet, tweet” up in a tree, it’s not just a pretty noise—the bird is trying to send a message. This animated video explores how and why birds communicate using sound. From the soft notes used by Northern Cardinals to keep in touch, to the fast trills of a Swamp Sparrow attracting a mate, birds use sound to send all sorts of messages. Their specialized voicebox, or syrinx, helps them do it, allowing birds to sing complex songs quickly. From the woods to the grasslands you hear birds wherever you go, and once you tune in you can begin to decode the language of birds.