1. Western Transportation Institute, Montana State University, P.O. Box 174250, Bozeman, Montana 59717 USA
2. Eco-Kare International, 644 Bethune Street, Peterborough, Ontario K9H 4A3 Canada
3. Australian Research Centre for Urban Ecology, University of Melbourne, Melbourne 3010 VIC Australia
4. University of British Columbia, Biological Sciences Building, Room 4200, 6270 University Boulevard, Vancouver, British Columbia V6T 1Z4 Canada