Epizootiology and Control of Avian Diseases
in Endangered Forest Bird Habitat
in South Kona, Hawaii

It is becoming increasingly clear that the accidental introduction of Culex mosquitoes, pox virus, and avian malaria (Plasmodium relictum) to Hawaii has been disastrous for most of Hawaii's endemic avifauna. Both epidemiological and experimental studies have shown that pox and malaria, and particularly malaria, are acting as significant limiting factors in mid and low elevation wet forests and continue to threaten the last high elevation populations of endangered forest birds.
The Alala (Corvus hawaiiensis) (right) is one of the most endangered forest birds in the Hawaiian Islands. Fewer than ten wild individuals are restricted to a single population on the southwest slopes of Mauna Loa Volcano on the island of Hawaii. This area, now part of Hakalau Forest National Wildlife Refuge, is also home to relict populations of endangered Akiapola'au (Hemignathus munroi), Hawaii Akepa (Loxops coccineus)(lower left), and Hawaii Creeper (Oreomystis mana) (lower right).

	The relative importance of avian malaria and pox in the decline of the Alala is still poorly understood. Anecdotal observations indicate that pox and malaria can be debilitating or fatal in juvenile crows, and may be a factor limiting recruitment of juvenile birds into the adult breeding population. The fact that Alala nest in mid-elevation (1,200-1,500 m) ohia-koa forests (left) where prevalence of malaria and pox in forest bird populations is highest and where mosquito vectors are common indicates that crows are at a high risk of becoming infected with these diseases.
Research that focuses on the epidemiology and control of these avian diseases is important because release of captive-reared, non-immune crows into existing habitats could be undermined if the introductions occur in areas or at times of the year when transmission of pox and malaria by the introduced mosquito vector (right) is intense. Natural recruitment of wild crows into the adult breeding population may be significantly reduced if non-immune juvenile birds are weakened by disease and made more susceptible to predators or environmental stress.
This study is addressing a number of important questions relevant to control of avian disease in Hawaii including 1) collection of blood samples from forest birds to identify low- and mid-elevation reservoir hosts for pox and malaria (upper right), 2) monitoring of adult mosquito populations (lower left) across elevational gradients to determine seasonal trends in population sizes, 3) detailed characterization of oviposition sites (lower right, arrow) for Culex mosquitoes and their relationship to habitat degradation by feral ungulates, and 4) evaluation of the effectiveness of environmental management for reducing mosquito populations.

Hawaiian Endangered Forest Birds

Epizootiology and Control of Avian Diseasesin Endangered Forest Bird Habitatin South Kona, Hawaii

Epizootiology and Control of Avian Diseases
in Endangered Forest Bird Habitat
in South Kona, Hawaii