Abstract
O2 consumption was measured to estimate basal metabolic rate in a variety of Malaysian birds. O2 consumption during the active phase of the circadian cycle was greater than during the resting phase. O2 consumption was lower than that of temperate species of the same weight by 30% during the active phase and 35% during the resting phase. Species that forage in the sun seemed to consume less O2 than those that forage in the shade.