The Greater flamingo (Phoenicopterus roseus) is one of the most recognizable species breeding in the Ebro Delta Natural Park. In 2019, high per- and polyfluoroalkyl substances (PFAS) concentrations were found in two months old flamingo chicks. Motivated by these findings and the global concern for PFAS contamination, we monitored flamingos PFAS exposure over a five-year period. The study aimed to assess PFAS contamination patterns in chick's blood, temporal trends, examine potential effects on their body condition, and identify potential contamination sources by analysing PFAS in water. We collected a total of 148 flamingo blood samples from 2019 (n = 47), 2022 (n = 51), and 2024 (n = 50), and water samples (n = 8) within the Natural Park.

All chicks from the three studied years presented PFAS in their blood, indicating a chronic and early-life exposure to these contaminants to the breeding colony. ∑PFAS concentrations ranged from 4.53 to 576 ng/mL, and PFOS, PFOA and PFHxS were detected in all individuals. In 2024, mean ∑PFAS were of 55 ng/mL, lower than those detected in 2019 (78.2 ng/mL) and 2022 (81.7 ng/mL) (p < 0.05). The PFAS decline was driven by lower PFOA and PFHxS levels, likely reflecting recent European regulatory measures. The body condition of flamingos was found to be higher in those years with higher total precipitation during the breeding season (p < 0.05), likely due to a higher productivity of feeding sites. Notably, individuals with higher PFHxS and PFHpA concentrations exhibited reduced body condition (p < 0.05). PFAS were detected in all water samples indicating widespread contamination in the area, with the highest concentrations in agricultural fields which are important flamingo feeding areas. Overall, this study provides evidence of early PFAS exposure in a Special Protection Area for Birds and demonstrates the value of incorporating contaminant biomonitoring into conservation programs.