1. Dept of Biology; Acadia Univ.; Wolfville NS B4P 2R6 Canada
2. Dept of Integrative Biology; Univ. of Guelph; Guelph ON N1G 2W1 Canada
3. Canadian Wildlife Service, Environment Canada; Ottawa ON K1A 0H3 Canada
4. Bird Studies Canada; Port Rowan ON N0E 1M0 Canada