What bird-inspired flying-machine design did Leonardo da Vinci study?

Leonardo da Vinci studied an ornithopter, a flying-machine concept designed to imitate the flapping wings of birds. The word ornithopter comes from Greek roots meaning bird and wing.

His notebooks contain many observations of bird anatomy, wing movement, and flight. He explored machines with wings operated by human muscle, including designs in which a pilot would use pedals, levers, or body movement to drive the wings. These studies were part of his broader investigation of air resistance and animal motion.

Leonardo’s human-powered ornithopters were not built into successful aircraft. A person cannot generate enough sustained power through muscle alone to flap wings of the necessary size. His work nevertheless contributed to the history of aviation by treating flight as a problem of mechanics, observation, and experiment.