Begging in Nestling Birds

Abstract

Interest in nestling begging arises from the theoretical conflict over resource allocation between parents and their offspring. This conflict was first proposed by Trivers (1974), who suggested that an individual offspring is selected to obtain a greater proportion of resources than the parent is selected to give. That is, a parent is equally related to each offspring in each brood by half, whereas a nestling is more highly related to itself (i.e., 1.00) than to its present or future siblings (i.e., 0.50-0.25, on average). Conflict between parent and offspring can be expressed throughout the period of parental care from conception through independence, during which offspring are selected to elicit parental investment for a period exceeding the optimum for the parent. Trivers (1974) suggested an offspring is able to “compete” effectively with its parent through psychological manipulation. By begging until its needs have been met, the offspring indicates its degree of distress (for example, its requirement for food) and thereby encourages a higher level of parental investment. In such a system, any offspring signaling a “dishonest” (excessive) level of need would benefit from receiving a level of parental