Fig. 10. Normal forces during vertical maneuvers of great cormorants as a function of the position inside the obstacle course. Each black line is the net normal force generated by a single bird (out of N=8 birds). The net force is calculated by summing the forces normal to the instantaneous swimming direction from the motion of the body, tail, neck and foot propulsion. The forces are calculated for the birds passing through the obstacle course at the highest difficulty level (0.36 m between barriers, see Fig. 1). Filled and open columns denote centrifugal force and the component of buoyancy that is normal to the swimming direction, respectively. These forces are estimated based a mean body mass of 2 kg and the average instantaneous swimming speed, swimming direction and turning radius (see text). All forces are positive when they are directed above the bird's trajectory and negative when they are directed below it. The vertical arrows point to the position of the barriers on the adjusted horizontal axis. The horizontal axis is the same as in Figs 5, 6, 7, 8, 9 to allow equivalent evaluation.