Diving-flight aerodynamics of a peregrine falcon (Falco peregrinus)

• Published in: PloS one 2014-02, Vol.9 (2), p.e86506-e86506
• Main Authors: Ponitz, Benjamin, Schmitz, Anke, Fischer, Dominik, Bleckmann, Horst, Brücker, Christoph
• Format: Article
• Language: English
• Subjects: Aerodynamics; Animal behavior; Animals; Biology; Birds; Cameras; Dams; Digital cameras; Digital imaging; Diving; Engineering; Experiments; Falco peregrinus; Falconiformes; Feathers; Flight; Flight paths; Flight, Animal; Flow; Flow (Dynamics); Flow separation; Fluid dynamics; Fluid-structure interaction; High resolution; High speed cameras; Image resolution; Mechanics; Models, Theoretical; Physics; Pictures; Reptiles & amphibians; Science Policy; Separation; Trajectories; Velocity; Veterinary Science; Wind tunnels; Zoology
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0086506

This study investigates the aerodynamics of the falcon Falco peregrinus while diving. During a dive peregrines can reach velocities of more than 320 km h⁻¹. Unfortunately, in freely roaming falcons, these high velocities prohibit a precise determination of flight parameters such as velocity and acceleration as well as body shape and wing contour. Therefore, individual F. peregrinus were trained to dive in front of a vertical dam with a height of 60 m. The presence of a well-defined background allowed us to reconstruct the flight path and the body shape of the falcon during certain flight phases. Flight trajectories were obtained with a stereo high-speed camera system. In addition, body images of the falcon were taken from two perspectives with a high-resolution digital camera. The dam allowed us to match the high-resolution images obtained from the digital camera with the corresponding images taken with the high-speed cameras. Using these data we built a life-size model of F. peregrinus and used it to measure the drag and lift forces in a wind-tunnel. We compared these forces acting on the model with the data obtained from the 3-D flight path trajectory of the diving F. peregrinus. Visualizations of the flow in the wind-tunnel uncovered details of the flow structure around the falcon's body, which suggests local regions with separation of flow. High-resolution pictures of the diving peregrine indicate that feathers pop-up in the equivalent regions, where flow separation in the model falcon occurred.