Leonardo da Vinci’s bird-inspired aircraft concept was an ornithopter.
An ornithopter is an aircraft designed to fly by flapping wings, rather than using fixed wings or a rotary rotor. Leonardo filled his notebooks with observations of birds and studies of wing structures, human muscle power, and mechanical linkages. His proposed machines generally placed a pilot in a position to operate large wings through pedals, levers, or other mechanisms.
Leonardo understood that human strength alone would make powered flapping flight extremely difficult. His designs therefore remained theoretical or experimental rather than becoming successful aircraft. Nevertheless, they show his effort to connect anatomy, engineering, and the physics of flight.
The word ornithopter applies to a whole class of aircraft, not one single Leonardo model. That makes it different from the aerial screw, which used a rotating helical surface, and from the parachute, which was intended to slow descent rather than create powered flight.