Testing Relationships between Energy and Vertebrate Abundance

Table 1

Possible factors affecting the strength of the energy/abundance relationship at both the intraspecific and interspecific levels. Q refers to the consumer resource requirements, R refers to the resource supply rate, I refers to intrinsic factors (e.g., biological traits), while E stands for extrinsic factors (e.g., environmental factors).

Variable	Intrinsic/Extrinsic	Possible factors (intraspecific level)	Possible factors (interspecific level)
Q	I	Age/Size structure of the populations considered	Body temperature, Phylogeny
	E	Average climatic conditions	Average climatic conditions
R	E	Competition intensity, predation level	Diet (when considering indirect measures of resource abundance such as satellite-based indices of primary productivity)
	I	Spatial location of the studied population within the distribution range of the species	Competitive skills, trophic position, social system