Studies examining an organism's response to environment change can yield insight into the adaptive value of phenotypic adjustments. It has been well believed that flexibility in a certain trait is adaptively and functionally important for organisms to cope with environment change. Basal metabolic rate (BMR) plays an important role in energy balance regulation in both small mammals and birds. The hypotheses of‘energy demand’of short-term adjustments in BMR proposes that birds are able to adjust the size of internal organs to cope with changes in food intake. In the present study, we examined the effect of temperature on BMR and evaporative water loss (EWL) in Chinese bulbuls (Pycnonotus sinensis). Birds were housed individually in cages (60 cm×60 cm×30 cm) under a 12L : 12D photoperiod at room temperature. Food and water were provided ad libitum. Subjects were adapted to the cages for at least one week, and then randomly assigned into either cold group, birds were exposed to 10 ℃ for 28 days or warm group, during which birds were exposed to 30 ℃ for 28 days. Metabolic rates (MR) and water content of air were measured using an open-circuit respirometry system (AEI technologies S-3A/I, USA) before and after the experiment. A‘U’tube (containing silica gel) was connected in series following the respiratory chamber and was weighed before the start and at the end of each measurement. After BMR measurements, birds were killed by decapitation and heart, liver, kidneys, gizzard, small intestine and total digestive tract were removed separately and weighed (to 0.1 mg). These organs were dried at 60 ℃ for 2 days to constant mass and weighed again (to 0.1 mg). BMR were (4.42±0.16) mL O₂ /g·h at 10 ℃ and (3.75±0.16) mL O₂ /g·h at 30 ℃. Difference in BMR after corrected for body mass was significant. When expressed as total BMR per bird (O₂ / h) it was also significant between the two groups. EWL averaged (0.30 ±0.02) (g H₂O/h) at 10 ℃ and (0.22 ±0.03) (g H₂O/h) at 30 ℃, and birds at 10 ℃ showed 36.4% EWL higher than at 30 ℃ (P < 0.05). In addition, birds at 10 ℃ had significantly larger sizes in liver, kidney, small intestine and total digestive tract than at 30 ℃. It suggests that energy requirements significantly increase in Chinese bulbuls at cold compared with birds at warm, which is likely associated with the increased sizes in the internal organs and digestive tracts. A significant elevation of evaporative water at cold may be partly due to the increase in oxygen consumption.