Measuring raptor prey-capture behavior during natural flight
1 Dept. Behavior and Brain Organization, Max Planck Institute for Neurobiology of Behavior, 53175, Bonn, Germany.
Birds of prey use a wide range of visual and behavioral strategies when capturing airborne prey. While many studies have tracked bird behavior during flight using a variety of approaches, a method for capturing behavior during flight, in combination with eye motion, with high resolution has not been developed. Here, we designed a head-mounted imaging system that allowed imaging of Harris’s Hawks (Parabuteo unicinctus) behavior as well as eye motion during prey capture in an outdoor arena. The high-resolution imaging system comprised of a light-weight, tether-free camera system that was mounted on the bird’s head and body. To maintain image stability throughout the entire flight, we designed a form-fitted hood enabling both a firm camera attachment, as well as a comfortable and unobtrusive fit for the bird to allow feeding. To elicit capture behaviors, we first trained Harris’s Hawks using a combination of falconry techniques and mock equipment with increasing dimensions and weights, allowing the birds to perform flights unaffected by the recording equipment. Using this approach we tracked the eye rotations during flight based behaviors that ranged from simple flights, between two stationary perches, to capturing airborne prey targets. The resulting high-resolution images were stable enough to allow quantification of eye and head rotations during flight, prey tracking and capture, and landing behaviors, without needing external ground-based camera systems. Together, we show that, by combining head-mounted camera and tracking systems with training, the behavioral and eye-motion strategies employed by birds of prey during flight can be quantified.