The mechanical power output of the flight muscles of blue-breasted quail (Coturnix chinensis) during take-off.

Blue-breasted quail (Coturnix chinensis) were filmed during take-off flights. By tracking the position of the centre of mass of the bird in three dimensions, we were able to calculate the power required to increase the potential and kinetic energy. In addition, high-speed video recordings of the position of the wings over the course of the wing stroke, and morphological measurements, allowed us to calculate the aerodynamic and inertial power requirements. The total power output required from the pectoralis muscle was, on average, 390 W kg(-1), which was similar to the highest measurements made on bundles of muscle fibres in vitro (433 W kg(-1)), although for one individual a power output of 530 W kg(-1) was calculated. The majority of the power was required to increase the potential energy of the body. The power output of these muscles is the highest yet found for any muscle in repetitive contractions. We also calculated the power requirements during take-off flights in four other species in the family Phasianidae. Power output was found to be independent of body mass in this family. However, the precise scaling of burst power output within this group must await a better assessment of whether similar levels of performance were measured across the group. We extended our analysis to one species of hawk, several species of hummingbird and two species of bee. Remarkably, we concluded that, over a broad range of body size (0.0002-5 kg) and contractile frequency (5-186 Hz), the myofibrillar power output of flight muscles during short maximal bursts is very high (360-460 W kg(-1)) and shows very little scaling with body mass. The approximate constancy of power output means that the work output varies inversely with wingbeat frequency and reaches values of approximately 30-60 J kg(-1) in the largest species.