Watch VoirFilms. Many factors are contributing to the decline in Hawaii’s forest bird populations, loss of habitat, climate change.. invasive species, but none more than disease. Avian Malaria and avian Poxvirus are spread by human introduced Mosquitoes. Historically, mosquitoes did not exist on Hawaii and native bird species never developed resistance to mosquito transmitted diseases. Because of this, mosquitoes have devastated many native bird populations.