1. Long Point Waterfowl and Wetlands Research Program/Bird Studies Canada; Port Rowan ON N0E 1M0 Canada
2. School of Renewable Natural Resources; Louisiana State University; Baton Rouge LA 70803 USA
3. Environment and Climate Change Canada; Canadian Wildlife Service; Ottawa ON K1A 0H3 Canada
4. Delta Waterfowl Foundation; Bismarck ND 58504 USA
5. U.S Geological Survey; Patuxent Wildlife Research Center; Laurel MD 20708 USA
6. Department of Veterinary Clinical Medicine; University of Illinois; Urbana IL 61802 USA