Fig. 2

Effect of 4 weeks acclimation to two different temperatures and photoperiods on the body mass and metabolic rate of Eurasian Tree Sparrows (Passer montanus). Birds were acclimated to either a warm (W = 30 °C) or cold (C = 10 °C) temperature combined with either a long (L = 16 h of light) or short (S = 8 h of light) photoperiod. a Body mass (M_b). b Mass-specific metabolic rate and total metabolic rate as a function of body mass. c, d Basal Metabolic Rate (BMR) as a function of body mass following acclimation to either a long (c), or short (d), photoperiod. The allometric equations representing the linear curves are BMR = 0.35M_b^1.27 for all birds, BMR = 0.48M_b^1.14 for the long photoperiod and BMR = 0.22M_b^1.40 for the short photoperiod treatment. Data are means ± SEM, and bars with different letters indicate significant differences, *P < 0.05, ***P < 0.001