JOSEF K. SCHMUTZ,' Department of Zoology, University of Alberta, Edmonton, Alberta T6G 2E9, Canada; RICHARD W. FYFE, Environment Canada, Canadian Wildlife Service, Room 1000, 9942-108th Street, Edmonton, Alberta T5K 2J5, Canada; DAVID A. MOORE, Alberta Energy and Natural Resources, Fish and Wildlife Division, Brooks Wildlife Centre, P.O. Bag 1540, Brooks, Alberta TOJ OJO, Canada; and ALAN R. SMITH, Environment Canada, Canadian Wildlife Service, Prairie Migratory Bird Research Centre, 115 Perimeter Road, Saskatoon, Saskatchewan S7N OX4, Canada.