EFFECTS OF HELPERS ON FEEDING OF NESTLINGS IN GREY-CROWNED BABBLER (POMATOSTOMUS-TEMPORALIS)

1. The benefits of helping behavior to recipients were studied by analyzing the factors that influence rates of feeding of nestlings by parents and helpers in Pomatostomus temporalis. 2. Considering the nestlings as recipients, no benefits were detected from helpers that would not have been received from the parents alone: total feeding rate was independent of the number of helpers. Total feeding rate was dependent on the energy needs of the nestlings and on environmental factors, such as temperature and rainfall. 3. Considering parents as recipients, benefits were detected in the form of energy savings. As the number of helpers increased, the feeding rates of parents declined in terms of both percentage (Fig. 1) and absolute feeding rates. The percentage of decline with each additional helper diminshed as the number of helpers increased up to four. With eight helpers there was little or no more savings to the parents than with four. 4. Helpers benefited from the presence of other helpers in the same way as adults, namely, by an energy savings (Fig. 1). 5. Feeding rates of nestlings by fathers and helpers were lower in the presence of dependent juveniles from a previous brood than in their absence. © 1978 Springer-Verlag.