What type of aircraft did Leonardo da Vinci design by studying birds' wings?

Leonardo da Vinci designed an ornithopter as a human-powered aircraft inspired by birds' wings.

An ornithopter is an aircraft that flies by flapping wings, rather than by using fixed wings, rotors, or lighter-than-air gas. Leonardo studied bird flight, wing structure, balance, and air movement in numerous notes and sketches.

His designs were exploratory rather than working aircraft. Human muscles cannot provide enough sustained power for a person-sized flapping machine of the type he envisioned. Leonardo's studies nevertheless helped connect artistic observation with early aeronautical engineering.

An ornithopter should not be confused with Leonardo's aerial screw, which used a rotating helical surface and is often described as an early helicopter concept.