The Energetics of Lifetime Reproductive Success in the Zebra Finch Taeniopygia guttata

Abstract

Recent studies that have shown that variation in avian foraging behavior can produce changes in reproductive success and survival have raised the question of the role of energy budgets in determining reproductive behavior and other life-history traits of birds. The study reported here describes how the daily energy budgets of breeding populations of the zebra finch Taeniopygia guttata influenced the rate at which broods were produced, the size of broods that could be success-fully supported by their parents, and the subsequent survival of the parents. This was examined by experimentally altering the net rate of energy gain of four populations of randomly chosen zebra finches. The experimental design increased the amount of time spent searching for food without altering the amount of food available or consumed, which resulted in differences in the daily energy budget. Zebra finches with low rates of energy gain spent more time and energy foraging and had less energy available for reproduction than did finches with high rates of energy gain. A decrease in energy available for reproduction increased the time interval between successive broods while decreasing average brood size, juvenile survivorship, and adult survivorship.