Food Limitation of Avian Reproduction: An Experiment with the Cactus Wren

Abstract

Food limitation of reproduction during the nestling stage was tested by supplementing food only during this stage in Cactus Wrens. Parents offered supplemental food fed their young more (volume per unit time) than unsupplemented parents in 2 yr of experimentation. In 1986, food—supplemented nestlings had greater mass and linear measures, whereas in 1987, most food—supplemented nestlings had greater mass, but not linear dimensions, than their controls. In 1986, survivorship of young both in the nest and during 4—6 wk after fledging, was greater with food supplementation than without. In 1987, survivorship differences were not significant. Food supplementation enhanced annual reproduction of parents because more food—supplemented Cactus Wrens laid second clutches than controls in 1987, the only year when this was examined. We conclude that food availability during the nestlings stage can limit present reproduction, enhance the likelihood of additional reproduction, or both, in Cactus Wrens.