Nestling Digestive Physiology and Begging

Abstract

As birds grow, increases in food intake rate are matched by increases in mass of the alimentary system and/or mass-specific enzyme activity. In overfed nestlings, digesta retention time seems to decline and food is digested less efficiently. These observations are consistent with the idea that digestive capacity limits food intake and thus growth. When this is so, successful information transfer between begging nestlings and parents reduces parental costs and increases family economy. Nestling begging signals and parental provisioning responses therefore represent a system with the potential to optimize nestling digestive efficiency. However, little is known about how begging signals reflect changes in food quality or increased nestling metabolic expenditures, and how parents might respond. Nestling digestion and the physiological mechanisms that control begging provide an important link between begging effort, nestling nutritional state and the information regarding offspring ‘need’ that parents have been selected to acquire from begging signals.