Visual guidance of target-oriented flight behaviours in birds

• Main Author: Walker, J
• Other Authors: Taylor, G
• Format: Thesis
• Language: unknown
• Published: 2019
• Subjects: Birds; Aerial views; Visual guidance; Falco peregrinus
• Online Access: https://ora.ox.ac.uk/objects/uuid:8c9ee694-9734-45d8-a77f-1ac0b321849f

Birds are highly dependent on vision to guide their flight during goal-directed tasks. They shift their visual attention primarily through head reorientation, with limited eye movement; however, measuring head orientation in free-flying birds is a significant technical challenge. While the gaze strategies of some birds have been studied in considerable detail in laboratory environments, studies of visual guidance in natural environments have largely been limited to inferences based on GPS-derived flight trajectories. This thesis aims to advance our understanding of how birds use their visual system to guide target-directed flight, using novel instrumentation to measure the gaze strategy of homing pigeons (Columba livia) and peregrine falcons (Falco peregrinus) flying in their natural environments. We use GPS-derived flight tracks to explore the visual mechanisms available to pigeons to compensate for wind drift, finding that they partially compensate for lateral displacement caused by the wind performing better than a naive strategy requiring no knowledge of the wind. We then describe the development of a custom-built sensor, incorporating a GPS receiver and head-mounted inertial measurement unit (IMU), which measures bird position and head orientation. Using this instrumentation, we find that pigeons coordinate angular head saccades with their wingbeats. Our results also reveal that vertical head stabilisation is enhanced when flying with flock companions, largely via increased wingbeat frequency. The focus of pigeons’ visual attention during homing flight is measured with the sensor, allowing specific points of interest to be identified in the landscape that do not lie on the bird’s track. Finally, we find that in the closing phases of predatory pursuit, peregrine falcons continuously track their target position using either their frontally or laterally facing fovea. Refined iterations of the exploratory technique developed here have the potential to revolutionise our understanding of large-scale spatial ...