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

• Published in: PLoS ONE
• Main Authors: Ponitz, B., Schmitz, A., Fischer, D., Bleckmann, H., Brücker, C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: PLoS 2014
• Subjects: TA Engineering (General). Civil engineering (General); Falco peregrinus; peregrine falcon
• Online Access: https://openaccess.city.ac.uk/id/eprint/12938/; https://openaccess.city.ac.uk/id/eprint/12938/1/Diving-flight%20aerodynamics%20of%20a%20peregrine%20falcon%20%28Falco%20peregrinus%29.pdf; http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0086506; https://doi.org/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.