SEASONAL AND DIURNAL VARIATION IN METABOLISM AND VENTILATION IN HOUSE SPARROWS

Abstract

Abstract Passerines that are year-round residents in temperate climates undergo seasonal acclimatization that facilitates maintenance of thermoregulatory homeostasis. These changes in thermoregulatory metabolism must be supported by equivalent changes in oxygen transport. We measured the effects of ambient temperature and time of day on metabolism and ventilation in House Sparrows (Passer domesticus) in summer and winter. House Sparrows were exposed to ambient temperatures (Ta) ranging from −12°C to 15.5°C in summer and 17.5°C in winter. Open-circuit respirometry was used to measure oxygen consumption (VO2) and ventilation was recorded using whole-body plethysmography. In both summer and winter, VO2 increased with decreasing Ta. VO2 was significantly higher during the active phase compared to the resting phase of the daily cycle in both summer and winter. Thermal conductance was significantly lower in nighttime birds compared to daytime birds. With increased oxygen demands, minute volume (VI) increase...