Meeting Abstract
The snow bunting (Plectrophenax nivalis) is an Arctic-breeding passerine that experience relatively harsh wintery conditions throughout the year. Although the species is well adapted for these environments, our recent work suggest that the species tolerance to moderate summer heat, especially when actively flying, might be low. Since the Arctic is warming faster than the rest of the globe, it is expected that summer temperatures at the time of chick provisioning might limit the birds’ scope for physical activity. Heat stress could therefore affect individual performance and reproductive success. Working at the northern edge of their breeding range (Alert, 82°N, Nunavut), we aimed at determining the limits of thermal tolerance in snow buntings and predicting the ambient temperature at which sustained locomotor activity (e.g. flight or chick provisioning) could lead to hyperthermia in chick-rearing birds. This required field measurements of basal metabolic rate (BMR), maximal thermogenic capacity (Msum) as well as minimal and maximal conductance (Cmin and Cmax). Our results show that inactive snow buntings have a surprisingly high heat tolerance (ambient temperature of 36°C) and a high cold tolerance (< -90°C) in standardized conditions. However, our data also show that for a sustainable activity level representative of the chicks provisioning period (4 X BMR), the additive effect of heat and activity could push the birds above their heat tolerance limit at a much lower temperature (12°C in summer), potentially forcing them to reduce provisioning efforts. Since buntings already experience this temperature during the Arctic summer, our data suggest that the species might be very limited in its capacity to cope with the predicted increase in Arctic temperatures in the nearby future.
