NASA believes that aircraft of the future can mimic the flight of birds, flying more efficiently and safely. This video shows what NASA has observed in the flight of an eagle that can be translated into a concept for a future aircraft. For example, just as a bird uses different feathers on its wings to control flight, aircraft wing shapes can be designed to change and adapt to constantly changing conditions of flight. Or, an aircraft can mimic the way a bird lands, greatly decreasing the amount of fuel and runway space required.

http://www.aero-space.nasa.gov/videos/eagle_morph.htm