The ability to digest different kinds of foods has an enormous influence on the kinds of foods chosen by animals, on how and when they feed, and on the rates at which they grow and reproduce. The influence of digestive studies on ecology and behavior, however, has been practically ignored. The application of digestive physiology has been hampered by a wide gap between detailed studies of digestion and absorption at the cellular and biochemical levels, and the measurement of food assimilation at the whole organism level. The analogy between the digestive systems of animals and chemical reactors provides a bridge that links measurements of digestive processes at the cellular and whole organism level into a integrative and predictive framework. Mathematical models based on chemical engineering principles will be used to generate and test productions about the digestive processes of birds feeding on nectar and fruit pulp. Our models also provide predictions about the feeding preferences of birds with different physiological traits, and thus provide a direct liaison between digestive processes and the ecologically relevant process of food selection. The digestive traits of animals are not fixed; within a span, they depend on acclimation to different diets. The influence of different diets on the digestive processes of birds with contrasting dietary habits, how changing a diet influences the ability to digest and absorb carbohydrates, lipids, and proteins, and how dietary changes influence these digestive processes at the cellular, organ, and whole organism levels, will be investigated. Chemical reactor theory will be used to integrate our results. In addition to providing a bridge between digestive physiology and ecology and behavior, our research will provide information on the digestive capabilities and limitations of birds in captivity, and in improving husbandry practices for both endangered species in zoological parks and animals with economic value.
