This paper describes how climate variation in time and space can constrain community structure on a global scale. We explore body size scaling and the energetic consequences in terms of absorbed mass and energy and expended mass and energy. We explain how morphology, specific physiological properties, and temperature dependent behaviors are key variables that link individual energetics to population dynamics and community structure.

This paper describes an integrated basic principles model for mammal energetics and extends the model to bird energetics. The model additions include molar balance models for the lungs and gut. The gut model couples food ingested to respiratory gas exchanges and evaporative water loss from the respiratory system. We incorporate a novel thermoregulatory model that yields metabolic calculations as a function of temperature. The calculations mimic empirical data without regression. We explore the differences in the quality of insulation between hair and feathers with our porous media model for insulation.

For mammals ranging in size from mice to elephants we show that calculated metabolic costs are in agreement with experimental data. We also demonstrate how we can do the same for birds ranging in size from hummingbirds to ostriches. We show the impact of changing posture and changing air temperatures on energetic costs for birds and mammals. We demonstrate how optimal body size that maximizes the potential for growth and reproduction changes with changing climatic conditions and with diet quality. Climate and diet may play important roles in constraining community structure (collection of functional types of different body sizes) at local and global scales. Thus, multiple functional types may coexist in a locality in part because of the temporal and spatial variation in climate and seasonal food variation. We illustrate how the models can be applied in a conservation and biodiversity context to a rare and endangered species of parrot, the Orange-bellied Parrot of Australia and Tasmania.