Fig. 5. Changes in acceleration parallel to the body fuselage (surge) throughout single swimming strokes by a Brünnich's guillemot (BRGU 13) during ascent. Plots are of deviations from the mean acceleration during an entire stroke (including upstroke and downstroke), based on regression equations fitted to accelerometer recordings at 0.03125 s intervals (32 Hz). Some curves represent pooled groups of strokes with similar curves (numbers of pooled strokes in parentheses). Periods of gliding separated almost all strokes, and only clearly recognizable strokes with acceleration peaks >1 m s^–2 were included. Other conventions are as in Fig. 4.