1. Department of Biology, University of Minnesota, Duluth, 1303 Ordean Court, Duluth, MN 55812 USA and Natural Resources Research Institute, University of Minnesota, 5013 Miller Trunk Highway, Duluth, MN 55811 USA
2. Hawk Ridge Bird Observatory, 3980 E Skyline Parkway, Duluth, MN 55804 USA
3. Natural Resources Research Institute, University of Minnesota, 5013 Miller Trunk Highway, Duluth, MN 55811 USA
4. US Environmental Protection Agency, Great Lakes Toxicology and Ecology Division, 6201 Congdon Boulevard, Duluth, MN 55804 USA and Hawk Ridge Bird Observatory, 3980 E Skyline Parkway, Duluth, MN 55804 USA