AeroVironment released a video of flight tests of its tiny Nano Hummingbird flapping-wing UAV in February 2011. It was built under DARPA’s Nano Air Vehicle (NAV) program.
This vehicle, like a real hummingbird, hovers, maneuvers and flies under its own power, using its flapping wings for propulsion and control. The final concept demonstrator, built under Phase 2 of DARPA’s NAV program, has a wingspan of 16 cm and weighs just 19 grams — less than an AA battery. Carrying batteries, motors, a video camera and communication links, it is bigger than the average hummingbird, but smaller and lighter than the largest of the species.
The remote-controlled Nano Hummingbird met or exceeded the Phase 2 goals, the company said. It demonstrated precision hovering within a 2 meter-diameter “virtual sphere;” stable hovering in wind gusts up to 5 mph; hovering endurance up to 8 minutes without external power; transition from hover to forward flight up to 11 mph; and flying from outdoors to indoors and back through a normal doorway. 
Warwick, Graham. “AeroVironment’s Nano Hummingbird Flies!” 2.17.2011. www.aviationweek.com