The Role of Tail Bending in Avian Aerodynamics and Flight Control

The avian tail plays a critical role in enhancing aerodynamics as well as flight control. In this study, high-speed 3D kinematic tracking of a lovebird (Agapornis roseicollis) was employed to capture detailed tail dynamics during maneuvering flight. A pronounced, time-varying spanwise bending behavior was observed to synchronize with wingbeat cycles and tail-spreading maneuvers. To evaluate the implications of this behavior, we developed a biomimetic robotic tail and conducted systematic wind tunnel experiments combining force measurements and time-resolved particle image velocimetry (TR-PIV). The PIV measurements elucidate that the spanwise bending causes vorticity to move from the central region toward the outside edges, which can substantially influence the aerodynamic forces and moments. Together with wing motion and variations in surface area, tail bending provides an additional aerodynamic mechanism for avian flight control.