1. Wildlife Health Laboratory, Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA
2. Section of Epidemiology, Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA
3. Bird Population Studies, Laboratory of Ornithology, Cornell University, Ithaca, New York 14853, USA