Trace element accumulation in hooded crow nestlings: tissue- and age-specific patterns and implications for avian...

Floodplain wetlands are dynamic ecosystems that may receive pollutants transported from upstream areas, but local exposure of wildlife to trace elements can vary depending on hydrology, bioavailability, habitat structure, and diet. In this study, we assessed the concentrations of potentially toxic non-essential elements (Cd, Pb, As) and essential elements (Cu, Se, Zn) in the blood and feathers of hooded crow (Corvus cornix) nestlings from a riverine wetland in Warta Mouth National Park, western Poland. Samples were collected at two developmental stages and analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Concentrations of Cd, Pb, and As were consistently low in both tissues, suggesting limited exposure and/or low bioavailability of these elements in the local food web used by this omnivorous wetland-associated species. Element concentrations varied with nestling age. Older nestlings had higher blood Cu and Se concentrations. In feathers, Cd and Cu concentrations were also higher in older nestlings, whereas Zn concentrations were lower than at the earlier growth stage. These age-related differences may reflect a combination of physiological regulation, growth requirements, tissue-specific deposition, feather development, and element-specific toxicokinetics. No significant relationships were found between blood and feather concentrations, indicating that these matrices provide complementary information on exposure during nestling development. Feather Zn concentration was positively associated with nestling body condition, whereas no such relationship was detected for potentially toxic non-essential elements. Our findings highlight the importance of considering tissue type, feather ontogeny, and nestling growth stage when interpreting trace element concentrations in avian biomonitoring.