What kind of winged aircraft did Leonardo da Vinci design by studying birds?

Leonardo da Vinci designed ornithopters, aircraft intended to fly by flapping wings like birds.

Leonardo closely observed bird anatomy, wing movement, balance, and airflow. His flying-machine studies included large wings operated by a person’s arms, legs, or mechanical linkages. The word ornithopter means a craft whose wings produce lift through flapping rather than through a fixed wing or a rotor.

Leonardo recognized that human muscle power was probably insufficient to flap wings large enough to carry a person. He still investigated the idea because bird flight offered clues about lift, propulsion, and control. His notebooks also contain concepts closer to gliders and rotary-wing machines, so not every Leonardo flying-machine drawing is an ornithopter.

No Leonardo ornithopter is known to have flown. The designs were theoretical investigations, not tested aircraft in the modern engineering sense. Their historical importance comes from combining anatomical observation with mechanical experimentation.