Models to predict feeding behavior at the level of consumption and use of energy involve either details of internal (physiological) controls or economic principles of regulation based on optimal (evolutionary) foraging theory. These two approaches will ultimately be related, but the former requires more information for specific predictions. The latter can provide predictions based on selected criteria for regulation. Meal sizes and feeding frequencies of hummingbirds are examined relative to two regulatory, criteria: maximizing rate of net energy gain and maximizing efficiency (intakes/expenditures) through a “crop emptying” model that incorporates energy intake from food and energy expenditures for short-term (meal to meal) maintenance and longer-term (overnight) energy storage. Experimental results suggest that the feeding behavior of hummingbirds is differentially sensitive to short-term and daily uses of energy. Changes in overnight energy storage requirements result primarily in changes in meal size, while changes in meal to meal maintenance requirements result primarily in feeding frequency changes. The economic models predict these responses. The feeding behavior of hummingbirds also appears to be sensitive to food quality, time spent flying to and from a food source, and costs associated with the weight of ingested food.