Chapter 45 - Regulation of body temperature: patterns and processes

Abstract

Birds regulate body temperature (Tb) around setpoint values through changes in metabolic heat production and evaporative heat dissipation, accompanied by behavioral adjustments of heat transfer via radiation, convection, and conduction. Although the active-phase Tbs of 38–42°C maintained during normothermy are broadly similar across taxa, there is substantial phylogenetic variation in heat tolerance and evaporative cooling capacity. There are also pronounced differences among orders in the capacity for hypometabolic states such as torpor, during which Tb may decrease to below 5°C. In terms of heat dissipation pathways, the last decade has seen the avian beak emerge as an important site of radiative and convective heat loss. The role of developmental plasticity in the ontogeny of thermoregulation, particularly as a determinant of heat tolerance later in life, is a field of enquiry with considerable relevance for predicting the performance of both domesticated and nondomesticated species under hotter future climates.