Falling on deaf ears: the adaptive significance of begging in the absence of a parent

Abstract

Nestling begging is widely accepted as a form of communication through which an offspring can indicate to its parent its requirement for food. The honesty of this information is thought to be maintained by the cost of the signal, yet the success of the interaction is dependent on the presence of both the signaller and receiver. This study investigates the incidence of begging events occurring in the absence of a parent in southern grey shrikes, Lanius meridionalis. These 'parent-absent' begging events were found to represent 15% of all begging events and a significant decrease was recorded with increasing nestling age. The effects of sensory development and learning as nestlings age are discussed in the context of parent-absent begging in open- versus cavity-nesting species. Latency to respond to previous parental stimuli was not associated with the occurrence of these begging events and there was some evidence that hunger was the motivation to beg in the absence of a parent. However, parent-absent begging events were found to occur in clusters, with the interval preceding the first event being significantly longer than the interval between subsequent events. If not associated with state, this might suggest reduced predation risk and/or energetic cost if begging occurs soon after a previous begging event. Study of begging in the absence of parents may therefore provide important and original insights into the nature of begging, and should form part of future work on offspring solicitation.