Origin and development of homoiothermy: A case study of avian energetics

Abstract

The study is based on the results of the integrated measurement of the energy expenditure at rest and common activity in birds belonging to various systematic groups. Homeothermy has formed in birds and mammals independently and in different geological ages. However, in both groups it originated as a side effect of selection for aerobic metabolism improvement that provided a higher level of activity. Advantages of having high and stable body temperature, which were inevitably related with metabolism intensification, led to development of thermoregulatory adaptations such as fur and feathers.