Birds inspired Leonardo da Vinci's flapping-wing flying-machine designs.
Leonardo carefully studied birds because he believed their anatomy and wing movements could reveal how humans might achieve flight. His notebooks contain observations about feathers, joints, balance, air resistance, and the relationship between wing motion and lift.
The resulting ornithopter concepts use flapping wings rather than the fixed wings of a glider or airplane. Some designs imagined a pilot powering the wings with arms and legs, while others used mechanical arrangements to amplify human effort. Human muscles, however, cannot provide the power needed for a practical man-carrying flapping machine.
Leonardo's work was not based on modern aerodynamics, and he never demonstrated a successful human-powered aircraft. Still, his bird studies helped establish a lasting connection between biology and flight engineering, now called biomimicry.