Fig. 5. Changes of (A) the foot stroke frequency, (B) the duration of power stroke (open symbols) and glide (closed symbols) and (C) the maximum acceleration of surges (open symbols) and heaves (closed symbols) during descent phase for 17 deep (>40 m) dives from three birds. Different symbols indicate different birds. Effects of depth on the frequency of strokes, duration of power stroke and glide, maximum heave acceleration were significant. To demonstrate these effects, linear regression lines are also given.