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 x_max, y_max and z_max, 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 x_im, y_im and z_im. 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.

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