25.3 Sunday, Jan. 4 13:45 How Birds Change their Gaze to Accommodate Rapid Transitions Between Flight Modes KRESS, D*; LENTINK, D; Stanford University, Stanford; Stanford University, Stanford email@example.com
Diurnal flying animals such as birds depend primarily on vision to coordinate their flight path during goal-directed flight tasks. To extract the spatial structure of the surrounding environment, birds are thought to use retinal image motion (optical flow) which is induced by motion of their head. During straight flight phases, proximity information can be obtained from optical flow, which is inversely proportional to the relative distance between surrounding objects and the head of the bird. In contrast, during turning flight, optical flow of surrounding objects is independent of proximity. It is unclear what gaze behaviors birds perform to support depth perception as they switch between flight modes. To analyze this, we measured the gaze behavior of rapidly turning lovebirds in a goal-directed task: take-off and fly away from a perch, turn on a dime, and fly back and land on the same perch. High-speed flight recordings revealed that rapidly turning lovebirds perform a remarkable stereotypical gaze behavior with saccadic head turns of up to 3000 degrees per second, as fast as insects. In between saccades, gaze orientation is hold constant. By comparing saccade and wing beat phase, we find that these superfast saccades are coordinated with the upstroke. During straight flight before the turn, lovebirds keep a high contrast edge in their visual midline. This visual behavior can be interpreted as object fixation. Similarly, before landing, the lovebirds fixate the landing perch. Our observations thus show that rapidly maneuvering birds use stereotypic gaze behaviors, including feature fixations to optimize visuo-motor flight control.