Abstract: Basal metabolic rate (BMR) is a key hub in the network of physiological mechanisms connecting life history traits. To understand the ecophysiological characteristics of migrator, we examined the physiological responses of Daurian redstart (Phoenicurus auroreus) to changes in temperature by measuring their body temperature (T_b) and metabolic rate (MR), and calculating thermal conductance (C) at temperatures (T_a) between 5 ℃ and 40 ℃. Ten Daurian redstarts (males) were used in this experiment, with an average body mass of 17.6±2.0 g. Food and water were supplied ad libitum. Oxygen consumption of birds was measured using an opencircuit respirometry system (TSE Instruments, Germany). T_b was measured during metabolic measurements using a lubricated thermocouple inserted in the cloaca, and the output was digitized using an Oakton thermocouple meter (Eutech Instruments, Singapore). C (mL O² g^-1·h^-1·℃^-1) at any given T_a was calculated from the formula: C=MR/(T_b-T_a). In the range of T_a from 5 to 35 ℃, T_b of Daurian redstarts remained constant, with an average of 40.3±0.1 ℃. The thermal neutral zone (TNZ) of Daurian redstarts was 25-35 ℃. The mean MR within TNZ (i.e. BMR) of the species was 50.25±1.35 mL O²·h^-1, which is 151% of the expected value from their body mass. When T_a was below 25 ℃, MR increased with the decline of T_a with a fitting equation of MR (mL O²·h^-1) =99.65-1.93T_a (r=-0.707, P<0.001). When T_a was higher than 35 ℃, MR increased with the increasing T_a, and reached 59.78±1.31 mL O²·h^-1 when T_a was 40 ℃. Average minimum C of redstarts was 0.17 mL O²·g^-1·h^-1·℃^-1 measured between 5 and 25 ℃, representing 111% of the expected value based on their body mass. The basic thermobiological characteristics of Daurian redstarts are high T_b, BMR and C, and wide TNZ, which might make them acclimatized to the environment and survive at cold areas.

Key words: Phoenicurus auroreus, basal metabolic rate, ambient temperature, thermoregulation.