1. Department of Natural Resources and the Environment, Cornell University, Ithaca, NY 14853
2. Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853
3. College of Veterinary Medicine, Cornell University, Ithaca, NY 14853
4. Department of Ecology and Evolution, Princeton University Princeton NJ 08544
5. Center of Excellence for Vaccine Research, Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CN 06269
6. Laboratory of Ornithology, Cornell University, Ithaca, NY 14850