1. U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, 6201 Congdon Boulevard, Duluth, Minnesota 55804, U.S. Geological Survey, Biological Resources Division, Environmental and Contaminants Research Center, 4200 New Haven Road, Columbia, Missouri 65201, U.S. Fish and Wildlife Service, 3817 Luker Road, Cortland, New York 13045, and Cornell University, Division of Biological Sciences, Section of Ecology and Systematics, Cornell...