Early life antioxidants predict first-migration survival in the White Storks (Ciconia ciconia)

Early-life conditions can shape individual performance and survival in wild animals, particularly in species undertaking long-distance migration. We examined whether physiological parameters measured in the blood of nestling White Storks (Ciconia ciconia), including oxidative stress biomarkers, hematological indicators, trace elements, and pesticide residues-were associated with survival during the first migratory journey to Africa. Using data from 38 GPS-tracked juveniles in western Poland, we applied Cox proportional hazards models to identify predictors of mortality. The final model revealed that higher concentrations of catalase (CAT) and glutathione (GSH) were significantly associated with reduced mortality risk, suggesting a protective role of antioxidant capacity. These findings are consistent with the hypothesis that antioxidants mitigate telomere attrition, a process shown to predict survival in free-living birds. Thus, antioxidant status in early life may influence migration outcomes both by buffering oxidative damage and by preserving telomere integrity. Survival was also positively related to immune-hematopoietic balance and the proportion of arable land surrounding the natal nest, likely because open agricultural landscapes provide more favorable foraging conditions than forested habitats, whereas birds from more forested habitats had higher mortality risk. Our study highlights the combined importance of physiological resilience and landscape context in mediating early-life survival during one of the most demanding phases of the White Stork's life cycle.