Avian Behavioral and Physiological Responses to Challenging Thermal Environments and Extreme Weather Events

Birds occupy habitats ranging from Antarctic ice shelves and Arctic tundra to low-latitude deserts and lowland rainforests, and so are exposed to the full range of climates present on Earth. Cold, hot, or variable (on a variety of temporal scales) thermal conditions can present significant thermoregulatory challenges to birds, which typically must maintain body temperatures within narrow physiological tolerance limits. Such challenges may occur in all stages of the annual cycle and in all life stages of birds, so the ability to adjust to these conditions is required to maintain stable populations through time. For this Research Topic, we broadly define a challenging thermal environment as one necessitating behavioral or physiological adjustments to maintain body temperatures at levels appropriate for continued physiological function.Avian abilities to respond to extreme cold and heat are defined by thermoregulatory capacities for heat production or dissipation, respectively. Behavioral responses to temperature challenges can reduce the necessity for and magnitude of physiological adjustments, so together, physiological capacities and behavioral responses determine the probability of survival in thermally challenging situations. Moreover, thermal conditions experienced during reproduction can affect parental investment in the nesting effort and, independently, alter the course of nestling development, with potentially long-term consequences. Behavioral responses to these conditions as well as physiological responses at multiple levels of organization, from organisms to molecules, allow birds to tolerate thermal challenges. Our knowledge of the mechanisms by which birds respond, the time course for such responses, and the impacts on fitness, however, remain incompletely understood. Studies examining behavioral and physiological responses of birds to extreme and/or seasonally variable climates have been a research focus for decades, but recent advances in methods of me