Codex on the Flight of Birds is a relatively short codex of circa 1505 by Leonardo da Vinci. It comprises 18 folios and measures 21 × 15 centimetres. 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.
