A Behavioral Investigation of the Thermal Solar Niche

Abstract

The means by which a species survives in different environmental conditions is central to thoroughly understanding its ecology, evolution, and conservation. As we face a warming climate, developing a more comprehensive picture of an animals’ energetic (specifically, thermal) limitations is critical. Although temperature is often considered the primary parameter governing an animal’s thermal state, water availability, wind, and solar energy are also important. The thermal effect of solar energy is often assumed but is rarely measured. Because behavioral adaptation can be a critical tool for survival in changing and highly variable climates, behavioral patterns in relation to environmental conditions such as solar energy serve as a central way to assess animal responses to climate change. To investigate this fundamental yet overlooked aspect of environmental stress on animals, I conducted a shade manipulation experiment to control the amount of solar energy exposure to free ranging house sparrows, Passer domesticus, and better understand the effects of solar energy, particularly at high summer temperatures, on animal behavior. As predicted, bird attendance increased with increasing shade relative to the surrounding exposed areas. In contrast to my predictions bird attendance also increased with increasing temperature. An interaction between temperature and the amount of shade was also an explanatory variable for house sparrow attendance, which demonstrates the complexity of thermal pressures on animals. This study shows that as we continue to assess and predict how animals respond to climate change, we should incorporate behavior and quantify additive thermal pressures such as solar energy.