Birds daily execute complex maneuvers out of reach for current UAVs of comparable size, and these capacities are a least partly linked to efficient flapping kinematics. This article describes research efforts contributing to the ROBUR project that aims at producing a bird-sized UAV relying on such advanced kinematics. First, a multi-objective evolutionary algorithm was used to provide insights about the range of key mechanical parameters required for a 0.5 kg UAV flying horizontally at different speeds. Optimization lead to a minimum energy consumption of 20-50 W/kg for a 10-12 m/s speed, with wing-beat frequencies between 3 to 5 Hz. The corresponding simulations indicate that wing folding would substantially decrease the power consumption (25-44%) at medium to high speeds. Then, these results guided the design of a parallel flapping-wing mechanism based on two connected rod-crank devices. Wing motion is produced by four position-controlled brushless motors and the corresponding kinematic model is described in this article. Wing folding mechanism design will be the subject of future work.