• antioxidants;
  • growth;
  • oxidative stress;
  • reproduction;
  • vertebrates

The interest shown by ecologists in antioxidants and oxidative stress as potential modulators of life-history trade-offs has expanded greatly in recent years. However, we still know very little about natural variation in oxidative damage and antioxidant capacity in free-living animals. In this study, we describe the natural variation in three components of oxidative balance in nestlings and breeding females in free-living Great Tits Parus major and Common Starlings Sturnus vulgaris in central Italy, and relate these to breeding conditions and life-history traits. Our results suggest that there are associations among oxidative physiology, reproductive activity, growth pattern and season in wild birds, but that the nature of these associations might be species-specific rather than general across species.