Environmental cues play important roles in the regulation of an animal’s physiology and behavior. Photoperiod acts as an environmental zeitgeber for seasonal acclimatization of thermoregulation in birds. It has been demonstrated that an animal’s body weight, energy balance, and basal metabolic rate (BMR) all are affected by photoperiod. The present study was designed to examine changes of plasticity of body mass, metabolic organs and metabolism which were affected by photoperiod alone in Chinese bulbul (Pycnonotus sinensis). Adult Chinese bulbuls were live–trapped by mist net in Wenzhou Zhejiang Province (27?29′N, 120?51′E) from March to April 2008. Twenty Chinese bulbuls were transported to the laboratory and caged (60?60?30cm3) under natural photoperiod and temperature for one week to acclimate to laboratory conditions. Then the birds were randomly assigned into either long photoperiod (LD; 16L:8D) or short photoperiod (SD; 8L:16D) for 4 weeks at a constant temperature (28℃)(n=10 each group). Food was provided in excess of the birds’ needs and water was supplied ad lib. Body masses to the nearest 0.01g were determined immediately upon capture with a Sartorius balance (model BT25S). Body masses of the birds were monitored once a week. Organ masses to the nearest 0.1mg were determined immediately upon capture with a Sartorius balance (model BS110S). Energy intake was measured in metabolic cages. Food residues and feces were collected in the first day and once a week (every seven day) throughout the 4-week study period, and then oven-dried at 60℃ to get constant mass and separated manually. The caloric contents of food and feces were determined by oxygen bomb calorimeter (C200, Germany IKA). Gross energy intake (GEI), gross energy excrete (GEE), digestible energy intake (DEI), and apparent digestibility of energy (hereafter referred to as digestibility) were calculated as follows: GEI (kJ/d) = dry matter intake ((g/d) ? energy content of food (kJ/g); GEE (kJ/d) = day mass of feces (g/d) ?energy content of feces (kJ/g); DEI (kJ/d) =GEI-GEE; Digestibility (%) = DEI/GEI ? 100%. Metabolic rate (MR) was measured by using closed circuit respirometer, and temperature was controlled by water bath (? 0.5℃). After the acclimation, SD birds showed significantly higher body masses, organ masses (liver and small intestine) and basal metabolic rate (BMR) coupled with much higher digestibility than LD organisms. However, the energy intake, energy excrete and digestible energy intake of SD birds were lower than those in LD birds. To summarize, photoperiod affected body mass, organ mass (liver and small intestine), BMR and energy budget of Chinese bulbul. Furthermore, the more significant changes could be seen in SD Chinese bulbul. And the result of the domestication with photoperiod verified “the hypothesis of central restriction”, that is some of the metabolic existed in the Chinese bulbul body have positive correlation with the BMR, central organ is one of the function to change the BMR of Chinese bulbul.