Exposure of bald eagle nestlings to contaminants on National Park Service lands within the Chesapeake Bay
We examined breeding performance (N=921) and nestling exposure (N=25 nests) to heavy metals (cadmium, lead, mercury), polychlorinated biphenyls (PCBs - 91 congeners) and organochlorine pesticides (OCPs - 11 compounds) for bald eagles nesting on National Park Service (NPS) and associated lands within the Chesapeake Bay (2016-2018). Nesting pairs on NPS lands were consistently more successful and had higher reproductive rates compared to other pairs along the James/York River study area but these differences were not statistically significant. Mean reproductive rates were above the level believed to be required for population maintenance for all areas examined. Blood concentrations of heavy metals were generally low and varied between metals examined. Cadmium did not exceed the level-of-detection (LOD) for any sample. Detection frequencies for Lead and Mercury were 86 and 100% respectively. Lead concentrations (range = 0.21-0.88, geometric mean = 0.49 ?g/g ww) were low and no sample exceeded the level (<10 >?g/dL) believed to represent background for raptors. Blood concentrations (range = 0.106-0.903, geometric mean = 0.335 ?g/g ww) of mercury were toward the lower to middle range of values reported from other studies of nestlings. Broods reared around lakes or tidal-fresh reaches had higher concentrations than broods reared around high-saline waters. No samples approached the general threshold (>3.0 ?g/g ww) believed to result in possible reproductive impacts. Total PCB concentrations estimated during this study (range = 1.35-23.51, geometric mean = 6.34 ng/g ww) were on the low end of values reported from other regions. A cluster of the highest values were found within the lower James River. However, the highest values represented approximately 10% of the threshold (190 ng/g ww) suggested for reproductive impairment and 50% of the threshold (36 µg/kg) suggested for no-observed-adverse-effect-level (NOEL). Total OCP concentrations (range = 0.87-8.78, geometric mean = 2.68 ng/g ww) were lower than those reported from most other populations. p,p'-DDE was the most widespread pesticide compound and accounted for 93% of the total OCP values. Concentrations of p,p'-DDE (range = 0.6-8.78, geometric mean of 2.41 ng/g ww) were all below the level suggested for reproductive impairment (28 ng/g ww) and below the NOEL (11.4 ng/g ww) for productivity. Total concentrations of PCBs and OCPs were positively correlated (r=0.62, P<0.01) suggesting that these classes of compounds have common exposure pathways.