Fig. 4
HR oscillation during blue petrels’ respiration. A ECG trace showing heartbeats and cyclical noise consistent with respiration. Dashes in the upper left corner compare the second and the fifth RR intervals and highlight the RR difference at successive phases of the respiration cycle. B Dot plot of instantaneous HR versus time showing cyclical changes of HR suggestive of RSA. C Comparison between basal HR during incubation and minimum and maximum HR during a respiration cycle (n = 6). ***p = 0.0004, F = 44,84 by one-way ANOVA; **p = 0.0031 and **p = 0.0031 with Dunnett’s multiple comparisons test of minimum or maximum versus basal HR during egg incubation; n = 6