1. U. S. Fish and Wildlife Service; Cheyenne WY 82009 USA
2. Environmental Studies Program; University of Colorado Boulder; Boulder CO 80309 USA
3. Department of Biology; University of British Columbia Okanagan; Kelowna BC V1V 1V7 Canada
4. School of Environmental and Forest Sciences; University of Washington; Seattle WA 98195 USA
5. Department of Biology; University of Maryland; College Park MD 20742 USA
6. Department of Biology; University of Utah; Salt Lake City UT 84112-9057 USA
7. College of Sciences, Koç University; Rumelifeneri, Sariyer 34450 Istanbul Turkey
8. Bird-Life International; Cambridge CB3 0NA UK
9. US Geological Survey, Wyoming Cooperative Fish and Wildlife Research Unit, Department of Zoology and Physiology; University of Wyoming; Laramie WY 82071 USA