THE ENERGETICS OF LIFETIME REPRODUCTIVE SUCCESS IN THE ZEBRA FINCH TAENIOPYGIA-GUTTATA

Recent studies that have shown that variation in avian foraging behavi or can produce changes in reproductive success and survival have raise d the question of the role of energy budgets in determining reproducti ve behavior and other life history traits of birds. The study reported here describes how the daily energy budgets of breeding populations o f the zebra finch Taeniopygia guttata influenced the rate at which bro ods were produced, the size of broods that could be successfully suppo rted by their parents, and the subsequent survival of the parents. Thi s 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 d ifferences in the daily energy budget. Zebra finches with low rates of energy gain spent more time and energy foraging and had less energy a vailable for reproduction than did finches with high rates of energy g ain. A decrease in energy available for reproduction increased the tim e interval between successive broods while decreasing average brood si ze, juvenile survivorship and adult survivorship.