Fig. 4. Metabolic rate of post-absorptive European shags during diving (triangles) and when resting on the water surface (circles) at various water temperatures. There was a significant negative relationship between metabolic rate and water temperature during diving. The regression line shows the average relationship for all shags, which takes into account variability between subjects. It is best described by y=28.461-0.671x (r²=0.69, N=3 birds, n=25 trials), where y is metabolic rate during diving and x is water temperature. During resting, there was a non-significant trend for metabolic rate to increase with a decrease in water temperature (N=3 birds, n=12 trials).