ABSTRACT
R. L. Marsh explains the need for conclusive demonstration of the site of, control of, and mechanism of nonshivering thermogenesis in birds and proposes that existing data could be interpreted in alternative ways. While mammals employ a combination of shivering and nonshivering thermogenesis during exposure to cold, shivering thermogenesis has traditionally been assumed to be the main by which heat production can be augmented above standard levels in birds during both chronic and acute exposure to cold. The chapter argues that birds like mammals can develop nonshivering thermogenesis (NST) in response to cold-acclimation/acclimatization, pharmacological treatment or diet. Major muscle groups not only are involved in locomotion and shivering thermogenesis, they are also implicated as the site of nonshivering thermogenesis. NST is shown by measuring heat production by indirect calorimetry and shivering activity by electromyography or accelerometry. Diet-induced thermogenesis is well known in mammals as a facultative way for dissipating excessive energy input.
