A view of bird's eyes -- Pigeons lock their eyes in place during flight

Vision in most animals follows a fixate-and-saccade pattern. Birds fixate their viewing direction, then rapidly shift this gaze through head and eye movements. We used a head-mounted eye-tracking system in flying pigeons to relate eye to head movement and map eye position within the head. After take-off, the birds increased pupil size and adopted a fixed and consistent eye position in their head. In different visual environments, eye position returned to within 1{degrees} during flight. When flying, the birds positioned their eyes close to the primary horizontal axes of their vestibular systems. Because visual neurons share a common reference frame with the vestibular system, a consistent flight gaze position may actively align vision with mechanosensation and facilitate perception of self-motion. One-Sentence SummaryA head-mounted eye-tracking system shows that pigeons adopt a consistent eye-in-head position during free flight