Fig. 5. Changes in body angle (open circles) and speed (filled circles) during descent and ascent, based on eight dives from two Brünnich's guillemots (BRGU), 14 dives from four common guillemots (COGU), nine dives from four razorbills (RAZO), 16 dives from three rhinoceros auklets (RHAU) and seven dives from two little penguins (LIPE). Maximum depths for these sample dives were all between 20 and 30 m. To illustrate the effects of current depth on body angle and swim speed, mean body angle was calculated for each of 1–2 m, 2–5 m, 5–10 m, 10–15 m and 15–20 m depths, and means ± 1 s.d. (vertical bars) across 1-s samples are shown. Statistical testing was done using all 1-s samples. Note that axes for descent and ascent differ.