Meeting Abstract
Water vapor in the air can influence heat exchanges between an animal’s body and its environment but, below the freezing point, as the air water vapor pressure is very low due to condensation, it is often assumed that the effect of humidity on small endotherm’s thermoregulation is negligible. However, a recent study showed that black-capped chickadees (Poecile atricapillus) from eastern Canada had higher maximal thermogenic capacity (Msum) on winter days with higher humidity. This suggests that the cooling effect of humid air might be perceived by birds even in cold environments. To test this hypothesis, we measured resting metabolic rate (RMR) of captive chickadees (n = 10) during exposition to two ambient temperatures (-10°C and 10°C) while receiving either dry air or air saturated with water vapor. Preliminary results show that birds had an RMR 43% higher when at -10°C than at 10°C but that RMR did not vary with humidity at any temperature. Our results therefore suggest that chickadees do not loose more heat when being exposed to humid air. Feather insulation may be involved in this process by preventing significant changes in water vapor of the air layer close to the skin.
