Codex on the Flight of Birds is a relatively short codex of circa by Leonardo da Vinci. It comprises 18 folios and measures. Now held at the Biblioteca Reale in Turin, Italy, the codex begins with an examination of the flight behavior of birds and proposes mechanisms for flight by machines. Leonardo constructed a number of these machines, and attempted to launch them from a hill near Florence. However, his efforts failed. In the codex, Leonardo notes for the first time that the center of gravity of a flying bird does not coincide with its center of pressure.