Fig. 5. Temporal changes in heart rate (beats min^–1; bottom), and depth (m; top) occurring during diving relative to the point of submergence and the points of surfacing, for long dives (240–250 s; red traces) and short dives (150–140 s; black traces). Each point is the mean ± S.E.M. of the mean values from 7 birds. The blue horizontal lines are mean ± S.E.M. of heart rate when ashore.