RT Journal Article SR Electronic T1 Metabolic power, mechanical power and efficiency during wind tunnel flight by the European starling Sturnus vulgaris JF Journal of Experimental Biology JO J. Exp. Biol. FD The Company of Biologists Ltd SP 3311 OP 3322 VO 204 IS 19 A1 Ward, S. A1 Möller, U. A1 Rayner, J. M. V. A1 Jackson, D. M. A1 Bilo, D. A1 Nachtigall, W. A1 Speakman, J. R. YR 2001 UL http://jeb.biologists.org/content/204/19/3311.abstract AB We trained two starlings (Sturnus vulgaris) to fly in a wind tunnel whilst wearing respirometry masks. We measured the metabolic power (Pmet) from the rates of oxygen consumption and carbon dioxide production and calculated the mechanical power (Pmech) from two aerodynamic models using wingbeat kinematics measured by high-speed cinematography. Pmet increased from 10.4 to 14.9 W as flight speed was increased from 6.3 to 14.4 m s–1 and was compatible with the U-shaped power/speed curve predicted by the aerodynamic models. Flight muscle efficiency varied between 0.13 and 0.23 depending upon the bird, the flight speed and the aerodynamic model used to calculate Pmech. Pmet during flight is often estimated by extrapolation from the mechanical power predicted by aerodynamic models by dividing Pmech by a flight muscle efficiency of 0.23 and adding the costs of basal metabolism, circulation and respiration. This method would underestimate measured Pmet by 15–25 % in our birds. The mean discrepancy between measured and predicted Pmet could be reduced to 0.1±1.5 % if flight muscle efficiency was altered to a value of 0.18. A flight muscle efficiency of 0.18 rather than 0.23 should be used to calculate the flight costs of birds in the size range of starlings (approximately 0.1 kg) if Pmet is calculated from Pmech derived from aerodynamic models.