Head-mounted camera for reconstructing outdoor behavior in freely flying birds

Capturing the fine details of behavior when animals perform complex tasks, such as prey pursuit and capture, in natural environments is a challenging endeavor. For birds of prey, commonly used tracking approaches, such as lightweight GPS and inertial measurement units, cannot simultaneously track the bird's position and the fine details of body part motion or moving external objects. Here we designed a head-mounted, tetherless, 4π camera system which, combined with a high-resolution environmental scan, enabled detailed three-dimensional measurement of both head position and orientation in freely flying Harris's hawks (Parabuteo unicinctus) performing aerial pursuit in the wild. This stable head-mounted imaging approach enabled reconstruction of flight trajectories in natural environments, detailed quantification of head motion, optic flow and target position, while the bird tracked and captured airborne targets.