Among the many introduced threats to the Hawaiian fauna, avian disease is one of the most devastating. Before the arrival of Europeans, there were no mosquitoes or other blood sucking insects in Hawaii. This also meant that there were no mosquito-borne diseases.
The first mosquitoes were introduced to Hawaii in 1826 and at least four additional species have arrived. These introductions brought with them two mosquito-transmitted avian diseases that have proven to have immense impacts on the island avifauna, the avian pox virus (Poxvirus avium) and avian malaria(Plasmodium
Avian pox causes large tumor-like swellings on the soft parts of birds including the legs, feet and around the eyes and beak. Avian pox now has infected birds from sea level to tree line. Native birds are more susceptible to infection than introduced species since they did not evolve with such threats.
Due to the novelty of the disease, avian malaria spread quickly in native birds. With no prior exposure or natural immunity to this disease, malaria
probably swept through remaining lowland native bird populations quickly after its arrival, hastening the extinction of several remaining bird species and decline the of
Current native bird populations on the Island of Maui are restricted mainly to high elevation forests where the malaria plasmodium does not survive. In the 1960, mosquitoes were restricted below 2500 ft but today that threshold is at 4500 feet. Continued climate change is a imminent threat to these remaining bird populations.