Fig. 8. The turning moments generated by the tail (solid black circles) and neck (open circles) as a function of the birds' position inside the obstacle course. The data are means ± s.d. from eight birds passing through the obstacle course at the highest difficulty level (0.36 m between the barriers, Fig. 1). Note the order of magnitude difference in the scale of the vertical axes. Red symbols are the angular acceleration of the body, which correlates with the moment of the tail. Vertical arrows denote the position of the vertical barriers. The horizontal axis is the same as in Figs 5, 6, 7 to allow equivalent evaluation.