Anand, Sachin; Le Pogam, Audrey; O'Connor, Ryan; Love, Oliver; Vézina, François

 - Abstract: The Arctic is warming nearly four times faster than the rest of the world, posing a serious threat for cold-adapted species living here. Species such as the snow buntings, a small Arctic breeding passerine, exhibit high cold endurance but poor tolerance to even moderately warm temperatures. Understanding the capacity of Arctic endotherms to acclimate rising temperatures is critical under the ongoing climate warming. One mechanism that can facilitate such adjustments is phenotypic flexibility, a reversible process that enables endotherms to modify their traits in response to environmental change. Seasonal acclimatization in thermoregulatory traits provides a pathway to study this flexibility, as it shows how organisms adjust to temperature variation in their environment. We measured seasonal acclimatization in heat tolerance traits i.e evaporative water loss, resting metabolic rate, body temperature in captive buntings housed outdoor aviaries exposed to the natural seasonal variations. We measured heat tolerance traits in both summer 2023 and winter 2024 to assess and compare the extent of acclimatization, with data analysis currently underway. Given their high cold tolerance, we predict buntings will exhibit limited variation in traits associated with heat dissipation. Studying the extent of phenotypic flexibility in Arctic endotherms to acclimate to warmer temperatures is a critical step to understand their capacity to face climate warming.