1. NC Cooperative Fish and Wildlife Research Unit, Department of Applied Ecology; North Carolina State University; Raleigh NC 27695 U.S.A.
2. U.S. Geological Survey, NC Cooperative Fish and Wildlife Research Unit, Department of Applied Ecology; North Carolina State University; Raleigh NC 27695 U.S.A.
3. School of Environmental and Forest Sciences; University of Washington; Seattle WA 98195 U.S.A.
4. Department of Applied Ecology; North Carolina State University; Raleigh NC 27695 U.S.A.
5. U.S. Geological Survey Patuxent Wildlife Research Center; Laurel MD 20707 U.S.A.