1. New York Cooperative Fish and Wildlife Research Unit; Department of Natural Resources; Cornell University; 211 Fernow Hall Ithaca New York 14853 USA
2. U.S. Geological Survey; New York Cooperative Fish and Wildlife Research Unit; Department of Natural Resources; Cornell University; 211 Fernow Hall Ithaca New York 14853 USA
3. U.S. Geological Survey; Patuxent Wildlife Research Center; 12000 Beech Forest Road Laurel Maryland 20708 USA
4. Department of Environmental Conservation; University of Massachusetts-Amherst; 118 Holdsworth Hall Amherst Massachusetts 01003 USA