Wind, a common factor in the natural environment, affects the behavior and energy budgets of different small bird species in various ways. The present study examines the correlation between wind speed and duration on the energy budgets of Eurasian tree sparrows (Passer montanus). Ninety adult P. montanus were live-trapped by mist nets in Qiqihar, Heilongjiang Province, China (47° 29' N, 124° 02' E) from November to December 2012. After adapting to captivity for one week at Northeast Forestry University's Wildlife Conservation Medicine and Ecological Security Research Center, they were randomly assigned to one of nine groups, which were exposed to winds of different speeds (0.2-0.4, 1.2-1.4, 3.2-3.6 m/s) and durations (1, 2, 4 h/d) for one week in otherwise constant laboratory conditions, such as available food, temperature ((21.0±1.0) ℃) and natural light cycle photoperiod. Each group of birds inhabited the same birdcage living space, including two feeders and a water source, which provided unlimited food and water. The wind direction was set to blow from the feeder location in the birdcage to ensure that the birds could forage while facing windward. Winds of different speeds were created by electric fans at varied distances from each birdcage; an anemometer and a timer were used to measure wind speed and duration, respectively. Isolation measures were taken to ensure the experiments for each group did not interfere with the effects of wind on other groups. The body mass of each bird (BS210S balance, Sartorius Instrument Co., Ltd., Shenzhen, China) was measured to 0.01 g immediately after grouping and measured again at weekly intervals over the period of wind acclimation and testing. Body temperature was measured every day to 0.10 ℃, during which there was no wind. Food, water intake and fecal discharge frequency were recorded once a day. Meanwhile, food residues and feces were collected on a daily basis during the experiment and their caloric content was determined using an oxygen bomb calorimeter (GR-3500, Guangdong Instrument Corp., Guangdong, China).
After acclimation, we found the body mass and body temperature of P. montanus exhibited no significant changes with variations in wind speed and duration. The energy budgets were significantly different between the nine experimental groups, including significant differences in the mass of food and water intake, energy intake, cooling energy of water discharged, digestible energy and assimilation energy (P < 0.01), and the fecal discharge frequency, fecal mass and energy (P < 0.05). Each unit of cooling energy of water discharge, digestion rate and assimilation rate showed no obvious change with different wind conditions (P > 0.05). The energy budgets among groups were remarkably different without considering the effects of initial body weight. In this paper, as wind speed increased, water intake and cooling energy of water discharge in this species declined proportionally (P < 0.001). Variations in wind duration resulted in significant differences in energy intake, fecal energy and discharge frequency (P < 0.01) for wind durations of 2 or 4 h. However, the final consequence of wind speed and duration created no significant differences in the energy budgets of P. montanus under different experimental conditions, after the effects of initial body mass were eliminated, which was based on double-factorial analysis of variance on the combined action of wind speed and duration. To summarize, the wind environment of this study's setting, which simulated common local conditions, had no significant effect on the energy budget in P. montanus.