IBAs - Bald Eagle Monitoring

Bald Eagle Biosentinel Project

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Audubon Minnesota is working with the National Park Service in the collection of blood and feather samples from nestling bald eagles along the Mississippi and St. Croix Rivers. These samples will be analyzed for their levels of targeted “persistent, bioaccumulative, toxicants.” Because of the bald eagle’s place at the top of the food chain they have proven to be good biosentinels of ecosystem health. Our study area includes the Mississippi National River and Recreation Area and the St. Croix National Scenic Riverway and in 2008 we extended sampling to the southern end of Lake Pepin.

We collect blood and feather samples from nestlings at about 5 to 9 weeks of age as well as addled (non-hatched) eggs if we find them. We sample every eaglet in a nest when possible, take measurements and band the birds as well. Typically we analyze only one sample from each nest, the added samples will provide an archive for assessing emerging contaminants in the future. Nests are sampled on the Mississippi River from Anoka through Lake Pepin and on the St Croix River between St Croix Falls and the confluence with the Mississippi along with 1 nest on the Minnesota River in Ft. Snelling State Park.

Contaminants that are deposited on land will often accumulate in aquatic systems because of transport in runoff, stream flow, and ground water. Hence, this monitoring program focuses on aquatic systems to monitor ecosystem health and to observe actual effects in wildlife. Our focus is on monitoring 6 contaminants; lead, mercury, DDT (including DDE & DDD), PFCs (16 telomers including PFOS and PFOA), PBDEs (9 congeners), and total PCBs. These 6 chemicals account for most of the impairment listings for the two river systems or have been identified as new and emerging compounds of concern. They are also some of the most toxic and pervasive compounds in the upper Midwest.

The National Park Service is doing a parallel study on the Apostle Islands and south shore of Lake Superior. We have summary results available from the first 3 years of the study. We found unmetabolized DDT in one of the 26 river nests we sampled in 2006 and 2007. The unmetabolized DDT suggests a recent, unknown source of this chemical, which was banned in North America in 1972. Mercury concentrations were lowest in the Greater Twin Cities and highest along the upper portions of the St. Croix and Namekagon Rivers where extensive wetlands contribute to methyl mercury production. Lead was highest in nestlings from the Twin Cities area, but generally low elsewhere. We found PBDEs in all nestlings sampled and our data suggest a near doubling along the south shore of Lake Superior over the last five years. Levels of PFOS were highest in the Greater Twin Cities area, followed by the Lake Superior nests, and lowest in the upper St. Croix River system.

Funding for the 2008 portion of the study was provided by the Minnesota Pollution Control Agency, the Weesner Foundation, and the National Park Service. All previous funding was provided by the National Park Service. We received valuable assistance from the Minnesota and Wisconsin DNRs, Ramsey County Parks, the Red Wing Conservation League, the Red Wing Environmental Learning Center, the Prairie Island Tribal Community, Carpenter Nature Center and Upper River Services.

More information on this project can be found here.