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

Graham N. Askew^1,*, Richard L. Marsh² and Charles P. Ellington¹

¹ Department of Zoology, Downing Street, University of Cambridge, Cambridge CB2 3EJ, UK and
² Department of Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA

View larger version (22K): [in a new window]   Fig. 1. Two-dimensional representation of the filming arena used to record the movements of the centre of mass of the quail during take-off. Two cameras were positioned normally at a distance A and B, respectively, from two calibrated screens. The two images recorded in the two cameras had dimensions represented by xmax, ymax and zmax, according to a right-handed three-dimensional coordinate system. The position of the centre of mass of the quail in the camera images was defined by the coordinates xim, yim and zim. The ‘real’ coordinates of the quail were calculated by correcting for parallax using equations 1–6. , , opening angles of the cameras; ', ', angles between the bird and the origin.

View larger version (28K): [in a new window]   Fig. 2. (A) Two-dimensional representation of a typical take-off flight in a quail, for the three coordinates describing its three-dimensional position (x, y and z), plotted with respect to time (t). Quadratic equations have been fitted to the position data, and the r2 values for these are shown. (B) Three-dimensional representation of the flight illustrated in A. The axes have been scaled such that they represent the size of the flight chamber. (C) Velocity of the centre of mass of the quail during take-off for the flight illustrated in A and B. The initial velocity of the bird (vmin) was 4.33 m s-1, and velocity increased to a maximum of 5.74 m s-1 (vmax) by the end of the flight. The rate of change of kinetic energy of the body was calculated using equation 9: (U1) The initial kinetic energy of the body is deducted in this calculation because at least some proportion of this may be contributed by the hindlimbs. , , , velocity of the centre of mass in the x, y and z directions, respectively.

View larger version (17K): [in a new window]   Fig. 3. Distribution of area (A) and mass (B) along the wing, which was divided into 11 strips of equal width, normal to the wing axis (C).

View larger version (26K): [in a new window]   Fig. 4. (A) Angle of wing segments over the course of the wing stroke. Raw data from the video recordings are shown by the + symbols. The lines are Fourier-smoothed data with three harmonics. (B) Muscle strain recorded using sonomicrometry and calculated as the change in muscle length relative to resting muscle length, LR. (C) EMG recordings of pectoralis muscle activity. (D) Moment of inertia of the wing segments and of the whole wing calculated on the basis of the mass of the wing strips and their distance from the shoulder joint over the course of the wing stroke. (E) Kinetic energy of the wing segments and of the whole wing calculated from the moment of inertia and angular velocity of the wing strips. Note, in D and E, that the calculations take into account both wings.

View larger version (15K): [in a new window]   Fig. 5. Wing position over the course of a wing stroke calculated from the Fourier-smoothed data showing the movements of the individual wing segments. (A) Upstroke; (B) downstroke. Relative time (ms) is indicated adjacent to the position of the wing tip and serves to give the sequence of successive wing positions. The movements of the wing tip, wrist and elbow joints, are also indicated (C).

View larger version (28K): [in a new window]   Fig. 6. Scaling of (A) pectoralis muscle power output and (B) net work per wing stroke with body mass Mb. Data are shown for the Phasianidae (open circles), pigeon and Harris’ hawk during take-off (from Table 5), for hummingbirds (Chai and Millard, 1997; Chai et al., 1997), ‘bees’ (euglossine bees, Euglossa imperialis; M. E. Dillon and R. Dudley, in preparation) and worker bumblebees (Cooper, 1993) during loaded hovering or loaded climbing flights. Scaling of (C) pectoralis myofibrillar power output and (D) net myofibrillar work per wing stroke (Wmyo) with body mass. In C and D, data are shown for the Phasianidae, pigeon, small hummingbirds and ‘bees’, calculated by assuming relative myofibrillar volumes of 0.85 (Kaiser and George, 1973; Kiessling, 1977), 0.47 (George and Berger, 1966), 0.50 (Suarez et al., 1991) and 0.55 (Casey and Ellington, 1989), respectively. Relationships that are significantly different from zero are denoted by *(P<0.05) and **(P<0.01).

View larger version (22K): [in a new window]   Fig. 7. Scaling of kinematic, morphological and muscle performance data in Phasianidae. (A) Total pectoralis muscle mass (Mp) versus body mass (Mb); (B) wing stroke frequency (n) versus body mass; (C) relative downstroke duration (DS%) versus body mass; (D) pectoralis muscle strain () versus body mass; (E) average shortening velocity (V) versus body mass. Data are from blue-breasted quail (Mb=43.6 g; this study), northern bobwhite (Mb=199.5 g), chukar (Mb=491.5 g), ring-necked pheasant (Mb=943.4 g) and wild turkey (Mb=5275 g) (Tobalske and Dial, 2000). Relationships that are significantly different from zero are denoted by *(P<0.05) and **(P<0.01).

View larger version (11K): [in a new window]   Fig. 8. Scaling of mean pectoralis muscle stress in the Phasianidae calculated from the mean take-off power, pectoralis muscle strain, muscle density and wingbeat frequency.