Falcon feathers pop up during dive

Similar to wings and fins with self-adaptive flaps, the feathers on a diving peregrine falcon's feathers may pop up during high speed dives, according to a study published in PLOS ONE on February 5, 2014 by Benjamin Ponitz from the Institute of Mechanics and Fluid Dynamics in Germany and colleagues.

Peregrine falcons are one of the world's fastest birds and may reach up to 200 miles per hour when diving. Scientists studying the body shape and wing contour of the bird want to better understand how they reach these high diving speeds while maintaining maneuverability. Researchers trained peregrine falcons to dive in front of a 200 foot dam, and scientists captured 35 dives with a stereo high-speed camera system and hi-res camera. The images allowed researchers to reconstruct the flight path and body shape of the falcon during certain flight phases, and to build a life size model of the falcons. They then analyzed the aerodynamics of the model bird in a wind tunnel.

Source: Here