The great majority of life on earth is dependent upon the sun; solar radiation is converted into edible carbohydrates by plants (via photosynthesis), these feed the primary consumers and they, in turn, become prey for animals higher on the food chain. Exceptions to this sequence are organisms deep within the earth or on the sea floor that feed on nutrients released by geothermal processes.
Across the Northern Hemisphere, the peak of energy transfer from the sun to the Earth occurs during the months on either side of the summer solstice, which falls on or about June 21. However, when it comes to the efficient transfer of energy to plants and animals, this period begins and ends a few weeks earlier (i.e. from early May to mid July). It is during this period when moisture is still abundant, leafy plants are exploding and the insect swarms have yet to do much damage. Taking advantage of this natural abundance, most herbivores and their predators give birth in May and June.
By mid July, excessive heat, decreasing moisture and insect predation begin to take a toll on the vegetation and the energy transfer is diminished accordingly. Of course, plants and animals have since stored much of the energy that they received during the peak season in the form of new growth, fruits, nuts and fat and will draw on this bounty during the darker and leaner months of the year.
