Thermoregulation and Oxygen Consumption during Terrestrial Locomotion by White-Crowned Sparrows Zonotrichia leucophrys gambelii

Publisher Website
Google Scholar
Abstract
We trained white-crowned sparrows to locomote (normal mixed gait) on the wiremesh substrate of a circular treadmill while we measured steady-state , evaporative water loss ( ), and intraperitoneal temperature ( ) at several treadmill speeds (0, 0.30, 0.35, 0.41, 0.46 km h⁻¹) and air temperatures ( , 10, 0, 12, and 25 C) at each speed. In birds at rest, increased as diminished, but was independent of when birds were locomoting. At any , increased linearly with treadmill speed (to a maximum of 44.1 C). At or lower, was a linear function of at all treadmill speeds but did not conform to this regression at ( at 0.35-0.46 km h⁻¹ was lower than expected). We hypothesize that is not a reliable index of thermal environment in this zone and should be replaced by the "operative temperature," . At all , was a linear function of treadmill speed, with a progressively diminishing slope that became zero at . The percentage of total heat lost by latent transfer increased with increasing but was independent of treadmill speed. From these data, we propose that the heat increment of locomotion progressively substitutes for the thermostatic requirement. At , is independent of treadmill speed, and it costs a white-crowned sparrow no more energy to move about and forage than it costs it just to sit still and shiver to produce thermostatic heat. This has important implications for the interpretation of ecological theories of optimal foraging.