EXPERIMENTAL-EVIDENCE FOR REGULATION OF FOOD DELIVERY TO STORM-PETREL, HYDROBATES PELAGICUS, NESTLINGS - THE ROLE OF CHICK BODY CONDITION

The existence of a possible feedback mechanism, causally relating the nutritional status of nestling British storm petrels to the subsequent rates of food provisioning by their parents, was examined using a supplementary feeding experiment. There were no differences in parental provisioning behaviour between experimental and control groups before the supplementary feeding regime commenced. Thereafter, chicks receiving supplementary food showed higher levels of body condition (attributable to the experimental protocol), and consequently received smaller and less frequent meals from their parents than controls. The total amount of food received by the experimental group (parental delivery plus supplementary food) was similar to the amount delivered by control parents, indicating compensatory regulation of provisioning. These results support earlier findings at the same colony but are in contrast to similar studies on other procellariiform species elsewhere. The demonstration of regulation of food delivery casts doubt on hypotheses relating slow growth and lipid accumulation of procellariiform nestlings to scarce and unpredictable food resources, and indicates that more recent explanations relating lipid deposition to chronic overprovisioning by the adults are untenable for this species. (C) 1995 The Association for the Study of Animal Behaviour