Video: Seagull Robot Takes Off And Flies On Its Own, Just Like the Real Thing | Popular Science: "SmartBird flies like a seagull thanks to an active torsion system combined with a complex control system. Its wings each consist of a two-part arm wing spar with an axle bearing on the torso. The wings and tail are the only mechanisms creating lift, and Festo engineers had to figure out bird flight in order to do it.
The company explains: “First, the wings beat up and down, whereby a lever mechanism causes the degree of deflection to increase from the torso to the wing tip. Second, the wing twists in such a way that its leading edge is directed upwards during the upward stroke, so that the wing adopts a positive angle of attack.”"