Motor learning and adaptation in bird flight

Birds are capable of performing elaborate flight maneuvers in variable environmental conditions. While flight is an adaptable and skilled motor behavior, we know surprisingly little about how birds master this ability. Across species, skilled motor behaviors show practice-related changes or improvements in performance and understanding which features of a motor behavior change with learning can lend insight into the constraints, flexibility, and optimization of motor behavior. Here, we combined high-speed video recordings and pose-tracking software to analyze the kinematics of thousands of flights in zebra finches over multiple days of flight training and over different distances. Small birds, such as the zebra finch, use an intermittent flap-bounding flight style that alternates between flapping phases and flexed-wing bounding phases. We found that birds increase their flight speed and the time spent bounding and reduce variability in the bound position over ten days of flight performance. These motor changes to flight show savings, as performance is maintained even after two months without flight experience. Moreover, these same parameters are adjusted when birds fly longer distances, indicating that they may be key to flight flexibility. We built kinematic models to determine what features birds might be optimizing toward with learning and found that the data was best fit by a model simultaneously optimizing for minimum energy and flight duration. Taken together, our data highlight that flap-bounding flight shows hallmarks of skilled motor learning and lend new insight into the function of bounds.