Thermoregulation and Metabolic Rates in Yakutia’s Small-Size Passerines in the Winter
The data on basal metabolism and thermoregulatory responses in small passerine birds in the winter, in the temperature range natural for Yakutsk, have been analysed. Common redpoll Acanthis flammea (Linnaeus, 1758), Eurasian tree sparrow Passer montanus (Linnaeus, 1758), and Eurasian bullfinch Pyrrhula pyrrhula (Linnaeus, 1758) were researched. In Common redpoll, the minimal metabolism rates (about 3.1 mlG<sub>2</sub>/g;h) were reported in ambient temperatures between 10 °C and 20 °C. At temperatures going down from 20 °C to -30 °C, oxygen consumption doubled at a rate of 0.06 mlO<sub>2</sub>/ g;h per 1 °C. In the Eurasian tree sparrow, the growth of metabolism began at the temperature decreasing to 10°C and continued to temperatures going down to -25 °C --30 °C. With the ambient temperature from decreasing from -20 °C to -30 °C, the metabolic rate was increasing by 0.06 mW<sub>2</sub>/g;h per 1 °C. The Eurasian bullfinch had a significantly higher level of minimal metabolism than the Eurasian tree sparrow, while the maximum metabolic levels were close in absolute values. The rate of metabolic growth in bullfinch was half as high as in Common redpoll and Eurasian tree sparrow.