Flight is the most common form of animal locomotion, and much is to be learned about evolution of flight design and performance. Avian flight performance appears to vary with body size in a systematic fashion, with small animals capable of hovering and flying over a wide range of speeds and larger birds being forced to locomote using an increasingly narrow window of flight styles, until the largest are rendered flightless. Although frequently cited, fixed-wing aerodynamic theory poorly describes or at least inadequately predicts features of avian locomotion. Important questions yet to be resolved concerning avian locomotion are: (1) how and why do animals of differing body sizes differ in performance?, (2) what are the metabolic (i.e., fuel consumption) and mechanical power (i.e., horse-power) costs during flight and can we accurately measure muscle (i.e., the motor) efficiency?, and (3) how do three-dimensional configurations of flight surfaces change over a range of flight styles and speeds? Locomotion is involved in nearly every aspect of animal life including, dispersal, food acquisition, predator avoidance, and finding mates. Locomotor agility, speed, power, and maneuverability typically differ among species, allowing them to successfully occupy differing environmental conditions. Results from the proposed studies will elucidate aspects of avian form and function, as well as have broader implications for the evolution of vertebrate biodiversity, body size, and locomotor strategies. Moreover, as we advance our knowledge of the biomechanical bases of locomotion in animals, it can provide important insights into design features of human-made locomotor machines, as was done by the great aeronauts of aviation history.
