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(P854) Assessing Risks to Resident Great Horned Owls in the Kalamazoo River Floodplain: The Exposure Assessment.
Strause, Karl1, Zwiernik, Matthew1, Moseley, Pamela*,1, Villeneuve, Daniel1, Blankenship, Alan1, Giesy, John1, 1 Michigan State University, E. Lansing, MI, USA
ABSTRACT- The Baseline Ecological Risk Assessment (BERA) for the Kalamazoo River site identifies resident great horned owl populations as one of the environmental receptor species with the greatest potential risk from terrestrial-based dietary exposure to PCBs. To verify modeled exposures to resident great horned owl populations at the site, site-specific exposures to PCB-containing floodplain soils were measured for nesting pairs of owls. Worst-case exposures to floodplain soils were successfully obtained by deploying over 40 artificial nesting platforms in a 70 mile reach of the Kalamazoo River floodplain, including two discrete exposed sites and two discrete control locations. By employing a comprehensive array of habitat assessment, population survey and site observation techniques to select nest locations, MSU biologists achieved occupation rates of 15% and 23% for the 2001 and 2002 field seasons. Rigorous nest observation activities provided for the collection of 14 egg samples and 12 blood samples from active owl nests, including multiple instances of re-nesting that provided tissue-based chemical exposure measurements from both fresh eggs and nestling plasma for the same breeding pair of birds. Nest site investigations also successfully located adult feeding perches (perch trees) associated with each active nest. Collection and forensic analysis of over 70 owl pellet and prey remains samples (n >500 discrete prey items) from active nests and feeding perches provide for accurate, site-specific characterizations of owl foraging habits and diet composition. Site-specific dietary composition (73% mammals, 27% birds) varied greatly from the proportions utilized in the BERA model. Dietary links to the aquatic system are identified (muskrat) along with a varied passerine component. These findings provide the basis for field collections and chemical analyses of prey species in owl forage and an estimate of potential average daily dose through ingestion of contaminated prey.
Key words: PCBs, Great Horned Owls, Ecological Exposure Assessment, Superfund
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