BUNDLE, M. W.; DIAL, K. P.: The metabolic power requirements of birds in flight

Measurements of the metabolic power required for birds to fly across their range of speeds, have produced power curves which can be broadly assigned to two categories: curves that are independent of speed and those that are roughly U-shaped. Tucker’s classic work with budgerigars is the primary example of a U-shaped power curve, while nearly all of the species measured since show flight costs that change little across the range of speeds for which measurements exist. While it is likely that other birds are subject to increased power requirements at either very low or very high flight speeds, empirical support for this statement is lacking. Previously, we have reported the strong agreement between the flight costs from four budgies flying in our wind-tunnel, to those originally reported by Tucker, further supporting the notion that budgies are the only birds known to conform with traditional aerodynamic theory. If this fundamental difference exists between budgies and all other volant birds, it may provide a convenient framework for which to investigate the factors that determine the cost and shape of avian power curves. To address the question of whether budgie flight during wind-tunnel experiments is fundamentally different than that of other species under similar conditions, we performed the following experiment. We trained, a closely related species to budgies, the cockatiel, and magpies to fly across a wide range of speeds while wearing a mask in order to collect their respiratory gases. In addition, we analyzed high speed film of these same birds flying with and without their masks on. Here, we present both metabolic and kinematic data from three species of birds, budgies, cockatiels and magpies flying across their range of flight speeds, in an attempt to address the mechanism behind the peculiarities of budgie flight.