1. Environment Canada, Canadian Wildlife Service, Pacific Wildlife Research Centre, 5421 Robertson Road, Delta, British Columbia, Canada, V4K 3N2, Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada, V5A 1S6, and Chemistry Department, University of British Columbia, 2075 Westbrook Mall, Vancouver, British Columbia, Canada, V6T 1Z3