Whether parents or their dependent offspring control provisioning and how resource allocation is mediated behaviourally are fundamental questions in the context of parent – offspring conflict. Vocalisations during feeding of chicks of a small long-lived seabird, the Wilson’s storm-petrel (Oceanites oceanicus), were recorded on King George Island, maritime Antarctic, to evaluate their information content and effects on regulating provisioning by the attending adult. A supplemental feeding experiment was conducted in order to verify empirical findings. During the control period chicks honestly signalled their nutritional need, they conveyed information about their body condition through the number and sound frequency of begging calls uttered during feeding sessions. Parents were responsive to the information communicated through solicitation behaviour and delivered larger meals to nestlings in a poorer state but within a certain range under the constraints of food availability. Adults attending artificial fed nestlings increased delivered meal sizes by 2 g, which equals one third of a usual feeding, as response to intensified begging of their supplemented chicks.