© 1997 International Society for Behavioral Ecology
research-article |
Food division in the Arabian babbler nest: adult choice or nestling competition?
Department of Zoology, Tel Aviv University, Hatzeva Field Study Center D.N.Arava 86815, Israel
ABSTRACT
Many studies have found that food division among nestmates is negatively correlated with hatrhing order. The hypothesis that feedings are distributed according to the provisioners' selection is compared here with the hypothesis that feedings are divided as a consequence of nestling competition. Food distribution among Arabian babbler nestmates was negatively correlated with hatching order and was so skewed that many last-hatched nestlings died as a consequence of starvation. No feeding preference was found between any adult and any given nestling. No difference was found in feeding distribution among parents, partial parents, and nonparents. When an older foreign nestling was introduced into the nest, adults fed the newcomer more intensively than their own offspring, implying that feeding division among nestmates was not determined by die feeders but by the nestlings' relative ability to obtain food. In two-nestling nests, the older nestling obtained 62% of the feedings, on average. However, following selective feedings of the second-hatched nestling by the investigator, which equalized the two siblings' feeding amounts by the end of their second day, no difference was found between their feeding rates. The relative advantage of the older nestlings was eliminated by introducing a barrier into the nest. Under these conditions, feedings were distributed equally among the nestmates. Since neither hatching order, previous priority order, nor individual identification were used by the provisioning adults, the proximate factor determining food division among the neslings appears to be the result of nestling competition
Key words: Arabian babbler, hatching order, kin recognition, nestling competition, parental care, provisioning, Turdoides squamiceps.