Data from: The oxidative cost of reproduction depends on early development oxidative stress and sex in a bird species

In the early 2000’s, a new component of the cost of reproduction was proposed: oxidative stress. Since then the oxidative cost of reproduction hypothesis has, however, received mixed support. Different arguments have been provided to explain this. Among them, the lack of a life history perspective on most experimental tests was suggested. We manipulated the levels of a key intracellular antioxidant (glutathione) in captive zebra finches (Taeniopygia guttata) during a short period of early life and subsequently tested the oxidative cost of reproduction. Birds were allowed to mate freely in an outdoor aviary during several months. We repeatedly enlarged or reduced their broods to increase or reduce, respectively, breeding effort. Birds whose glutathione levels were reduced during growth showed higher erythrocyte resistance to free radical-induced hemolysis when forced to rear enlarged broods. This supports the hypothesis predicting the occurrence of developing programs matching early and adult environmental conditions to improve fitness. Moreover, adult males rearing enlarged broods endured higher plasma levels of lipid oxidative damage than control males, whereas adult females showed the opposite trend. Since most previous studies reporting non-significant or opposite results used females only, we also discuss some sex-related particularities that may contribute to explain unexpected results