The Use of Standard Operative Temperature in the Study of the Thermal Energetics of Birds

Abstract

Standard operative temperature, Tes, is an index of sensible heat flow to the environment which may be used as the independent variable for plotting thermoregulatory responses to complex thermal environments. The metabolic rate of the White-crowned Sparrow is a single-valued function of Tes for different wind speeds and radiation levels. The evaporative cooling rate of the White-crowned Sparrow may be a single-valued function of Tes above the lower critical temperature for different wind speeds and radiation levels, as long as humidity is low. As Tes may be defined equal to the temperature of the usual darkened, free-convection laboratory enclosure, it may be possible to extrapolate certain classes of published laboratory data on thermal physiology to natural environments at the same Tes.