Much attention has been focused on climate warming and the dangers of an increase in prevalence of mosquito-borne pathogens around the world, including zoonosis shared between humans and animals. Avian malaria has increased at upper elevations in Hawaii, even at elevations too cool for malarial development in the mosquito vector. Three haplotypes of avian poxvirus occur in Hawaii, and a virulent one (canary pox) shares the same vector as avian malaria in Hawaii, so it too should increase in incidence, driven by the greater vector capacity of upper elevation populations of Culex quinquefasciatus. It is possible to test this prediction with Hawaiian birds at 1900m elevation, and we show that mosquito –transmitted poxvirus now effectively limits population size of species within the entire community. Although molecular methods greatly increase the precision by which conservation biologists can identify ongoing threats, action to halt or reverse the damage caused by introduced pathogens will require adopting diverse strategies, including the culling of alien species to reduce competition for resources and allow time for disease resistant genotypes to spread. Hawaiian birds are teaching us new insights into how evolutionary reversals in morphology and behavior can be tracked using accurate molecular taxonomies that nest haplotypes island by island, but these populations are, unfortunately, continuing to disappear before our eyes.