You may know them as Alvin’s little friends who love to sing in the movie Alvin and the Chipmunks, but in reality, chipmunks really love to chirp and use their harmony to communicate with each other.

Here, we’ll explore the inside of the duck’s mouth and learn more about their bills and what they use them for. Then, we’ll check out their gizzard and find out just why ducks eat rocks. We’ll go over ...