Flight Mechanics and Constraints on Flight Performance

Flight is the major mediator of migration in birds. Compared to other modes of locomotion, high travel speed and low energy for given range have encouraged the evolution of long-distance migration. Flight mechanics makes an important contribution to the study of migration, most obviously by computing flight performance (primarily power output and flight speed). The aerodynamic properties of flapping wings impose constraints on flight activity which are often overlooked or are poorly understood. It is usually taken for granted that birds can select freely from a range of flight speeds, varying wingbeat kinematics to ensure force equilibrium, but this has never been tested. From the mechanical properties of muscle it can be argued that birds should be able to fly efficiently only within certain ranges of wingbeat kinematics; since kinematics must vary with speed, muscle properties represent a potential constraint on choice of flight speed. This paper reviews approaches to the estimation and measure...