Flight respiration and energetics

We use a comparative approach to examine some of the physiological traits t hat make flight possible. Comparisons of related fliers and runners suggest that fliers generally have higher aerobic metabolic capacities than runner s but that the difference is highly dependent on the taxa studied. The high metabolic rates of fliers relative to runners, especially in insects, are correlated with high locomotory muscle cycle frequencies and low efficience s of conversion of metabolic power to mechanical power. We examine some fac tors that produce variation in flight respiration and energetics. Air tempe rature strongly affects the flight metabolic rate of some insects and birds . Flight speed interacts with flier mass, so that small fliers tend to exhi bit a J-shaped power curve and larger fliers a U-shaped power curve. As bod y size increases, mass-specific aerobic flight metabolism decreases in most studies, but mass-specific power output is constant or increases, leading to an increase in efficiency with size. Intraspecific studies have revealed specific genetically based effects on flight metabolism and power output a nd multiple ecological correlates of flight capabilities.