Curious about why bird diseases may show up in a seasonal pattern? See Citizen Science Reveals Annual Bird Migrations Across Continents, courtesy eBird and the Cornell Lab of Ornithology, which helps illustrate how avian influenza may show up in the US in spring and fall. Wild birds are great travelers, and Avian Influenza virus may spread read more Migratory Bird Patterns: Animation from Cornell Lab of Ornithology