1. Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
2. Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4R2
3. Department of Ecology and Evolutionary Biology, Museum of Vertebrates, Laboratory of Ornithology, Cornell University, Ithaca, NY 14853, USA
4. Bird Studies Canada, Delta, British Columbia, Canada V4K 3N2
5. Environment and Climate Change Canada, Saskatoon, Saskatchewan, Canada S7N 0X4
6. Département de Biologie, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1
7. Ecosystem Science and Management Program, University of Northern British Columbia, Prince George, British Columbia, Canada V2N 4Z9
8. Alaska Songbird Institute, Fairbanks, AK 99708, USA
9. Oklahoma Biological Survey, University of Oklahoma, Norman, OK 73019, USA
10. Behavioral and Molecular Ecology Group, Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA
11. Beaverhill Bird Observatory, Box 1418, Edmonton, Alberta, Canada T5J 2N5
12. Ontario Ministry of Natural Resources, Peterborough, Ontario, Canada K9J 7BS
13. Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
14. Department of Environmental Studies, UNC Asheville, Asheville, NC 28804, USA
15. Department of Biology, Acadia University, Wolfville, Nova Scotia, Canada B4P 2R6
16. Department of Biology, Appalachian State University, Boone, NC 28608, USA
17. Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, LA 70118, USA
18. Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA 50011-1020, USA