HEDRICK, TL; TOBALSKE, BW; DIAL, KP; BIEWENER, AA: Power Output of Cockatiels: A Musculo-skeletal and Aerodynamic Approach

Measurements of pectoralis muscle power output were obtained in cockatiels (Nymphaticus hollandicus n=5, 97.4g) trained to fly in a wind tunnel over a wide range of speeds (1 – 14 m/s). Pectoralis muscle force was measured via a deltopectoral crest mounted strain gauge, muscle strain via sonomicrometry and muscle activity via electromyography. Pectoralis force, work, and power were scaled using our estimates of aerodynamic power required at an intermediate flight speed (mean of 7 and 9 m/s) based on a 3D kinematic analysis of the flights. Contrary to published results using magpies, we observed a markedly U-shaped curve for pectoralis power as a function of speed; power output increased to a greater degree at high speeds (11 – 14 m/s). Muscle mass-specific power output was 207 W/kg at 1 m/s and 270 W/kg at 14 m/s. Minimum power speed was 7 m/s at 94 W/kg, maximum range speed was 9 m/s at 104 W/kg. The pectoralis power and estimated aerodynamic power curves were similar at speeds less than 11 m/s. At higher speeds, our model underestimated observed pectoralis power. This suggests that 1) the pectoralis muscle provides most of the power necessary for flight, even at slow speeds and 2) our estimated values for parasite and profile drag were too low. Pectoralis strain ranged from 32 to 45%, consistent with use of the pectoralis for work production. Fractional lengthening of the pectoralis decreased and fractional shortening increased as flight speed increased. Supported by NSF IBN-0090265.