Fig. 7. Graphic representation of the different equations available to estimate rate of oxygen consumption from heart rate using the equations from Froget et al. (2001) when the animal is resting (solid line) or active (walking on a treadmill, grey line) or using the equation from the present study (broken line). The regression equations are derived from a hypothetical bird with a bill length of 123.8 mm and a body mass of 12.2 kg. The black circles represent the estimated rate of oxygen consumption when the animal is resting on sea water.