1.1 Body temperature and diurnal cycle of energy metabolism at different ambient temperatures (+2 to +25°C) were tested for 18 different hummingbird species from different biotopes and of different body-masses (2.7–17.5 g).2.2. The level of resting metabolism (night time) reaches 30–70% of activity metabolism values (day time). The mean is almost exactly 50%.3.3. The mean metabolism-weight regression line of the night time values follows the equation M = 0.67 × W0.73 (M = energy metabolism in kJ/hr, W = body weight in g). That of the day time values is M = 0.83 × W0.53.4.4. Resting metabolic rate of the hummingbirds is considerably higher than the theoretically expected value for nonpasserine birds, even when torpor values are taken into account.5.5. All species tested show torpor during night time, independent of ambient temperature, feeding situation or the environment (biotope) of the species.6.6. In comparison to the resting metabolic rate, metabolism during torpor decreases by 60–90% to a relatively constant level. This level is not (linearly) temperature-dependent (m = 0.008. r = 0.22), nevertheless many species show a minimum at ca 15–20°C.7.7. During torpor, body temperature normally reaches the level of the ambient temperature but never falls below 18–20°C. The normal values during the daytime range from 38 to 40°C and during night time from 35 to 37°C.