Recent advances in the mechanistic understanding of avian responses to environmental challenges

Endothermic species have evolved strategies to maximize survival in highly variable or extreme environments. Birds are exemplary as they are among the most widely distributed endotherms on the planet, living in all manner of inhospitable environments. As an example, winter in temperate regions is characterized by cold temperatures and low food availability. Some birds have evolved to tolerate these conditions by seasonally increasing thermogenic capacity, increasing heterothermy, and displaying highly flexible phenotypes. Other species have evolved to avoid the inhospitable conditions of winter altogether by migrating—again requiring a unique set of physiological adaptations that allow success in this challenging endeavor. In these examples and in many others, the organismal requirements for success share similarities, but the underlying mechanisms, physiological requirements, and selection on those traits can differ significantly, as can their ecological and evolutionary impacts. In recent years, a suite of novel and established tools has become widely available and more accessible, allowing insights into long-standing questions. Genomic tools, new approaches to measure organismal performance, the use of citizen science data, easier access to metabolite assays or hormone detection, to name a few, have spurred rapid advances in our understanding of avian physiology. These new tools have been leveraged to investigate important questions regarding avian responses to our rapidly changing climate in an attempt to understand species resilience and limits.