Environmental contaminants in excrement of Iowa's nesting and wintering Bald Eagles (Haliaeetus leucocephalus)

Abstract

Bald Eagles (Haliaeetus leucocephalus) were rare only a few decades ago but have undergone a spectacular recovery range-wide. While their numbers have increased, there is concern about exposure of Bald Eagles to environmental contaminants. We collected excrement from nesting and wintering Bald Eagles in Iowa to examine their exposure to several contaminants and tested for differences as a function of space, time, and breeding status. We detected aluminum, copper, manganese, and zinc at levels above the quantitation limit (QL) in most excrement samples. These elements are all essential micronutrients normally found in living organisms. Arsenic and selenium are essential micronutrients for which fewer samples had levels above the QL. We also detected non-essential elements barium, cadmium, lead, and mercury in excrement samples, although only one sample had a cadmium level above the QL and only 26% of samples had lead levels above the QL. Geometric mean contaminant levels in excrement samples collected from nesting eagles during the spring were higher than for samples collected in the winter for aluminum, barium, copper, manganese, and zinc. The only difference we detected in contaminant levels in excrement samples was in manganese (higher for nest sites along the Mississippi River) and selenium (lower for nest sites along the Mississippi River) versus nest sites not associated with the Mississippi River. We also found that non-breeding eagles had higher levels of barium and manganese than nesting eagles. Our results can serve as a baseline for comparison with future studies investigating exposure of Bald Eagles to environmental contaminants. ABSTRACT.-Bald Eagles (Haliaeetus leucocephalus) were rare only a few decades ago but have undergone a spectacular recovery range-wide. While their numbers have increased, there is concern about exposure of Bald Eagles to environmental contaminants. We collected excrement from nesting and wintering Bald Eagles in Iowa to examine their exposure to several contaminants and tested for differences as a function of space, time, and breeding status. We detected aluminum, copper, manganese, and zinc at levels above the quantitation limit (QL) in most excrement samples. These elements are all essential micronutrients normally found in living organisms. Arsenic and selenium are essential micronutrients for which fewer samples had levels above the QL. We also detected non-essential elements barium, cadmium, lead, and mercury in excrement samples, although only one sample had a cadmium level above the QL and only 26% of samples had lead levels above the QL. Geometric mean contaminant levels in excrement samples collected from nesting eagles during the spring were higher than for samples collected in the winter for aluminum, barium, copper, manganese, and zinc. The only difference we detected in contaminant levels in excrement samples was in manganese (higher for nest sites along the Mississippi River) and selenium (lower for nest sites along the Mississippi River) versus nest s...