Physics of Flight in Birds (and Hummingbirds)

Birds display remarkable features of aerial maneuverability and control of unsteady aerodynamic forces that, to date, have no technological parallel. Stability in flight requires force and moment balances attained via bilateral symmetry in wingbeat kinematics, whereas rapid changes in body roll, pitch, and yaw derive from bilaterally asymmetric movements of both wings and the tail to generate rapidly changing torques that enhance agility in rotation. Anatomical constraints on wingbeat kinematics can limit total force production and thus axial agility (e.g., linear acceleration) in some circumstances. Using the example of hummingbirds as a model system, I will introduce kinematic, aerodynamic, and biomechanical features of avian flight performance, outline experimental perturbations based on variable-density gas manipulations (e.g., altitudinal ascent), illustrate amazing control of flight through small apertures and in highly turbulent regimes, and broadly delineate future opportunities for evaluating the low-Reynolds number unsteady aerodynamics and fluid physics that form the basis of aerial control and maneuverability in this very diverse group of flying animals.