For a view of bird flight from an engineering perspective, and for an amazing embodiment of the principles involved, you must check out this link: http://www.coolestone.com/media/2342...e-a-REAL-Bird/. Be sure to have the sound up, and view full screen.
Although the narrative of the video relates only to the propulsion aspects of the bird's flight, some remarkable electronic controls must also have been employed to guide the flight and to return the bird to its handler. Quite amazing!
Interesting bit of engineering and planning...that machine really moves like a gull I also got a kick out of all the audience members trying to get "BIF" images with their point-and-shoot devices!