Loge(daily energy expenditure in kJ day-1) measured using the doubly-labelled water (DLW) technique for free-living animals as a function of logeMb (in g) for (A) 73 small mammals and (B) 90 birds. Loge(daily energy expenditure in kJ day-1) measured using the doubly-labelled water (DLW) technique for free-living animals as a function of logeMb (in g) for (A) 73 small mammals and (B) 90 birds. See text for statistics. John R. Speakman J Exp Biol 2005;208:1717-1730 © The Company of Biologists Limited 2005