Patterns and trends in lead (Pb) concentrations in bald eagle (Haliaeetus leucocephalus) nestlings from the western Great Lakes region
Most studies examining bald eagle (Haliaeetus leucocephalus) exposure to lead (Pb) have focused on adults that ingested spent Pb ammunition during the fall hunting season, often at clinical or lethal levels. We sampled live bald eagle nestlings along waterbodies to quantify Pb concentrations in 3 national park units and 2 nearby study areas in the western Great Lakes region. We collected 367 bald eagle nestling feather samples over 8 years during spring 2006-2015 and 188 whole blood samples over 4 years during spring 2010-2015. We used Tobit regression models to quantify relationships between Pb concentrations in nestling feathers and blood using study area, year, and nestling attributes as covariates. Pb in nestling feather samples decreased from 2006 to 2015, but there was no trend for Pb in blood samples. Pb concentrations in nestling feather and blood samples were significantly higher in study areas located closer to and within urban areas. Pb in feather and blood samples from the same nestling was positively correlated. Pb in feathers increased with nestling age, but this relationship was not observed for blood. Our results reflect how Pb accumulates in tissues as nestlings grow, with Pb in feathers and blood indexing exposure during feather development and before sampling, respectively. Some nestlings had Pb concentrations in blood that suggested a greater risk to sublethal effects from Pb exposure. Our data provides baselines for Pb concentrations in feathers and blood of nestling bald eagles from a variety of waterbody types spanning remote, lightly populated, and human-dominated landscapes.
Key wordsBald eagle nestlings Blood and feather samples Censored data Haliaeetus leucocephalus Lead (Pb) pollution National Park Service
We thank the many employees and volunteers at the national parks that assisted with logistics and field sampling. We also appreciate the in-kind support of state, federal, tribal, and non-governmental partners. We thank D. Andersen, J. Glase, B. Lafrancois, C. Morris, D. VanderMeulen, and 2 anonymous reviewers for their technical review of earlier drafts of the manuscript. Use of trade names does not imply endorsement by the U.S. Government or the University of Minnesota.
Major funding was provided by the U.S. National Park Service, Great Lakes Inventory and Monitoring Network, the National Park Service Biological Resources Division, and the Minnesota Pollution Control Agency. The Wisconsin Department of Natural Resources and Ramsey County (MN) Parks and Recreation provided in-kind support for bald eagle occupancy and productivity flights. JEB was supported as a Research Fellow during data analysis and manuscript preparation at the U.S. Geological Survey, Minnesota Cooperative Fish and Wildlife Research Unit at the University of Minnesota.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.
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