The explanatory power of the lift equation in the wingbeat kinematics, motor control, and evolution of animal flight

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The ultimate goal of my research program is to answer two intertwined questions: 1) How do birds incorporate sensory information from the head, body, and wings, and generate motor commands for controlling the flapping motion and dynamic shape of wings in response to aerodynamic challenges? 2) How do mechanisms of flight control shape the evolution of flight and diversity of flight performance in birds? Flying birds must modulate and balance force with extreme precision to perform different behaviours, but how birds do this is not well understood. Aerodynamic force is determined by air density (ρ), wing velocity (V), wing size (specifically area A), and a force coefficient (CF) that accounts for the wing’s shape and presentation as it encounters the oncoming air. Total force is equal to ½ρV2ACF, and this simple equation is broadly applicable in fluid mechanics. Previous studies of how animals modulate force considered only individual components of the force equation, but, through recent advances, we can now apply more challenging methods to examine these elements in concert. The force equation can be divided into two fundamental strategies for force generation: modulation of wing velocity (V), and morphing of wing size and shape (A and CF). My research group, one of the leading laboratories in avian flight, has recently proposed that this physical division of the force equation is reflected at multiple levels of avian flight control including anatomy, muscle physiology, and wingbeat kinematics. Our ultimate hypothesis is that the physiological and biomechanical mechanisms for modulating force through wing velocity and morphing determine individual performance and shape the evolution of major avian clades. The goal of this Discovery Grant application is to determine how birds simultaneously control wing velocity and wing morphing to modulate force production. We will investigate the representation of the force equation at three levels of biological organisation: 1) Evolutionary comparisons of force modulation in hovering hummingbirds. 2) Inter- and intra-specific trade-offs in wing velocity and wing morphing for modulating aerodynamic forces. 3) Neuromuscular control of wing velocity and wing morphing. This research will add significantly to our understanding of how flying animals modulate aerodynamic force. This approach will transform the field of animal flight by revealing how the aerodynamic force equation is expressed at multiple levels of biological organisation. This integrative research makes use of diverse approaches, and will provide a range of training opportunities for HQP. The discoveries have the potential to alter textbook understanding of muscle physiology, animal flight mechanics, and ornithology, and will also provide a guidepost for bioinspired engineering of aircraft and in robotics.