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

In the early 2000s, 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 for 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 haemolysis when forced to rear enlarged broods. This supports the hypothesis predicting the occurrence of developing programmes 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. As 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.

Nestling erythrocyte resistance to oxidative stress predicts fledging success but not local recruitment in a wild bird

Stressful conditions experienced by individuals during their early development have long-term consequences on various life-history traits such as survival until first reproduction. Oxidative stress has been shown to affect various fitness-related traits and to influence key evolutionary trade-offs but whether an individual's ability to resist oxidative stress in early life affects its survival has rarely been tested. In the present study, we used four years of data obtained from a free-living great tit population ( Parus major ; n = 1658 offspring) to test whether pre-fledging resistance to oxidative stress, measured as erythrocyte resistance to oxidative stress and oxidative damage to lipids, predicted fledging success and local recruitment. Fledging success and local recruitment, both major correlates of survival, were primarily influenced by offspring body mass prior to fledging. We found that pre-fledging erythrocyte resistance to oxidative stress predicted fledging success, suggesting that individual resistance to oxidative stress is related to short-term survival. However, local recruitment was not influenced by pre-fledging erythrocyte resistance to oxidative stress or oxidative damage. Our results suggest that an individual ability to resist oxidative stress at the offspring stage predicts short-term survival but does not influence survival later in life.