Figure 1.

The relationship between adjusted oxygen uptake and dive duration in five cormorants foraging on either sedentary or motile prey. Oxygen uptake is adjusted to mean duration of the surface period (13.4 s), mean dive depth (5.6 m) and mean bird mass (2.1 kg). Regressions: sedentary prey, solid, =1.68x+60.4, R²=0.23; motile prey, dashed, =2.66x+37.6, R²=0.38. Grey lines indicate 95% confidence limits. The region of non-significance (see text) is the range of dive durations where the elevations of the two regressions are not significantly different. Inset: mean adjusted oxygen uptake+s.e.m. for dives for sedentary prey (filled bars) of 10, 20 and 30 s and for dives for motile prey (open bars) of 10, 20, 30 and 40 s.