Bioaccumulation of Trace Elements in White Storks (Ciconia ciconia): Effects of Age, Health, and Anthropogenic Exposure

Abstract

White storks (Ciconia ciconia) are recognized as effective bioindicators of environmental contamination due to their wide distribution and trophic flexibility. In this study, we analyzed blood concentrations of 47 essential, toxic, and potentially toxic elements in 189 white storks from central Spain, assessing the influence of age, health status, and anthropogenic pressure on metal accumulation. Birds were grouped into chicks, fledglings, and adults. Statistical comparisons were performed using non-parametric tests and general linear models (GLMs), depending on data distribution. Our findings indicate that age significantly affects metal accumulation, with fledglings exhibiting higher concentrations of lead (Pb, p = 0.0024), arsenic (As, p = 0.0012), cadmium (Cd, p = 0.0476), and manganese (Mn, p = 0.0467) compared to adults, suggesting increased exposure through parental feeding and trophic transfer. Health status was also a critical determinant: sick individuals showed significantly elevated levels of Cd (p < 0.0001), Pb (p < 0.0001), and As (p = 0.0166), supporting the role of metal toxicity in avian morbidity. In terms of anthropogenic exposure, storks sampled within 30 km of landfills exhibited significantly higher concentrations of As (p = 0.0002), Cd (p = 0.0118), and Hg (p = 0.0412). Individuals with foreign materials in the digestive tract also showed increased Pb (p = 0.0007) and Cd (p = 0.0008) levels. Conversely, no significant differences were found between individuals from areas of high versus low human population density. These results highlight the impact of environmental pollution on metal bioaccumulation in white storks and demonstrate the influence of landfill proximity and trophic exposure on contaminant burdens. Given their role as a sentinel species, our findings underscore the need for stricter waste management policies and continued biomonitoring efforts to mitigate toxic metal exposure in wildlife.