The optimum flight speeds of flying animals

Conventional models of bird Eight combine metabolic, mechanical, and aerody namic components to calculate the rate of fuel consumption and power requir ed for flight, from which we may derive the optimal speeds Eying animals sh ould use in different situations. These models contain the implicit assumpt ion that the metabolic and mechanical components of power output are consta nt and show no systematic variation with speed. This assumption underlies t he optimum flight speeds, optimum climb protocol, maximum endurance and max imum Eight range predicted by these models. Here we consider alternatives to the assumption that power is independent o f speed and show that if the aerodynamic power output from a constant rate of fuel consumption varies with Eight speed, then the optima derived from c urrent models of animal Eight need to be revised. In some cases (e.g. optim um Right speeds) the current models give answers that are only quantitative ly wrong, but in some cases (e.g. optimal cruising altitude) current models give answers that are qualitatively wrong.