Fig. 2. The instantaneous horizontal speed (U; calculated from the displacement of point 11 in Fig. 1B) of the great cormorant during an average paddling cycle. Each symbol represents the instantaneous speed of one bird (mean of five runs). The solid line (black squares) is the mean of all birds (N=9). The acceleration of the body (power phase) occurs during most of the stroke phase (first six fields) followed by a deceleration until the next stroke phase. The X axis is the proportion of the cycle duration normalized by dividing the period of each phase (stroke, glide and recovery) by the mean duration of that phase (see text).