Birds have an ability to fly through obstacles by shifting their shape in flight, which is difficult to reproduce in uncrewed aerial vehicles, commonly known as UAVs or drones. A new study from researchers at the University of Oxford and the University of California, Davis, published March 4 in Journal of the Royal Society Interface , shows how researchers can begin to approach this challenge, leading to insights into how birds fly and to improved UAV designs.
Kiran Weston and Professor Graham Taylor from the Oxford Flight Group, with doctoral student Huanglun (Adam) Zhu and Christina Harvey , assistant professor at the UC Davis Department of Mechanical and Aerospace engineering, used a combination of motion capture and wind tunnel modeling to see how a Harris’s hawk changes its wing and tail shape as it flies through a narrow gap.
Found in arid areas of the U.S. Southwest, Mexico and South America, Harris’s hawks hunt as a team, often flushing out prey and flying around trees and cacti. Like most birds, they can rapidly shift from gliding flight to tucking in their wings to avoid obstacles.
The researchers used motion capture imaging at Oxford’s flight hall to film a Harris’s hawk gliding from one perch to another. They placed a pair of soft poles in the flight path to create a narrow gap, encouraging the bird to tuck its wings as it flew through.
After analyzing the video, they constructed models of the hawk’s wing and tail at different points in the maneuver and tested them in the wind tunnel facility at the UC Davis College of Engineering. Models were made from resin 3D printing thanks to support from the UC Davis Engineering Student Design Center.
They found that when the hawk tucks its wings, it shifts from an unstable to a stable state. In aerodynamics, being unstable makes a flying object highly maneuverable, like a jet fighter, while being stable means it can maintain a steady course.
The results suggest that birds control their flight differently than traditional aircraft, as human-built aircraft usually do not shift between stable and unstable states in this way.
UC Davis has recently completed its own flight hall, the Center for Animal Flight and Innovation, equipped with motion capture and high-speed video technology. The center will bring new insights into bird flight and potentially, drone technology. Construction and equipment of the center was funded by a grant from the U.S. Army Combat Capability Development Command Army Research Laboratory.
Funding for the current study was provided by the Air Force Office of Scientific Research and the David and Lucile Packard Foundation.
Journal of The Royal Society Interface
Experimental study
Animals
Stability shifts in gliding flight: hawks morph from an unstable to stable state when navigating a gap
4-Mar-2026
The authors declare no competing interests.