Winter energy requirements of blue grouse

We measured the effects of temperature (Ta) on the metabolic rate of 6 blue grouse (Dendragapus obscurus) during winter with indirect respiration calorimetry. The standard metabolic rate was 0.812 L O2∙(kg0.734)−1∙h−1 and was 24% higher than that predicted allometrically. The lower critical temperature (Tlc) of fasted grouse was −5 °C; metabolism increased linearly below −5 °C. The heat increment associated with a Douglas-fir (Pseudotsuga menziesii) diet lowered the Tlc by 5 °C From −5 to −20 °C, the metabolism of fasted and fed grouse increased by 30 and 12%, respectively. A positive winter energy balance was predicted for blue grouse from estimates of the field metabolic rate and the consumption and assimilation rates of a Douglas-fir diet.