Measuring an organism's response to a changing environment can yield an insight into the adaptive value of phenotypic adjustments. However, it is not clear how an organism translates seasonal acclimatization to temperature acclimation. In the present study, we measured resting metabolic rate (RMR), evaporative water loss (EWL) and internal organ masses in seasonal acclimatized adult Chinese bulbuls (Pycnonotus sinensis) that were captured in winter and summer, and bulbuls that were acclimated to 10℃ (cold) and 30℃ (warm) in laboratory for four weeks. We also measured state 4 respiration and cytochrome c oxidase (COX) activity in liver and muscle of these birds. RMR was measured using an open-circuit respirometry system. State 4 respiration and COX activity in liver and muscle mitochondria were determined at 30℃ using a Clark electrode. Winter- and cold-acclimated birds showed significantly higher RMR, EWL and internal organ masses, as well as state 4 respiration and COX activity than their summer- and warm-acclimated counterparts. The adaptive adjustment of organ masses and cellular thermogenesis might partly contribute to the variability of RMR. The findings suggest that Chinese bulbuls exhibit adaptive adjustments in some physiological and biochemical traits in response to changes in seasonal environment and the changes in temperature only, which can be employed to cope with fluctuations in environmental conditions. These data test the hypothesis that physiological flexibility in energetic traits is a common feature of avian metabolism.