Predicting and mitigating the threat of avian disease to forest birds at Hakalau Forest National Wildlife Refuge

A small orange and brown bird with a metal band around its leg is held gently by a hand
The endangered Hawaiʻi ʻAkepa is one of the smallest honeycreepers and is found in native ʻōhiʻa and koa forests above 4500 feet elevation, like in the Hakalau Forest National Wildlife Refuge. (Photo: Carter Atkinson, USGS)

Hawaiʻi’s native forest birds are known worldwide for their diversity and beauty. Unfortunately, many species are heading towards extinction because of bird malaria spread by mosquitoes introduced over a century ago. Remaining populations of these highly threatened forest birds tend to be at high elevations near the tree line on mountains, where cooler temperatures limit mosquitoes and malaria development. With rising temperatures in those upslope areas due to climate change, mosquitoes and disease are starting to be found at higher elevations. In addition to warming temperatures, increasingly dry conditions change stream flow allowing for the creation of pools that provide additional larval mosquito habitat in riparian areas where larval mosquito habitat has been historically limited. Research suggests that within a few decades’ changes in climate conditions for all habitat areas for Hawaiian forest bird populations will increase to levels that allow for the invasion of mosquitoes and malaria. Managers and researchers are turning to methods of controlling mosquitoes in these forests as a way of aiding native bird populations.

This project will research what key habitats in the forest are used for mosquito larvae and when those habitats allow mosquitoes to develop. There are three basic goals to the study: (1) collect physical data to understand and forecast climate change impacts, (2) determine the larval mosquito habitat and mosquito productivity of riparian corridors; and (3) develop a model that assesses the abundance of mosquitoes under a suite of management and climatic conditions. Field studies will be conducted in Hakalau Forest National Wildlife Refuge (where mosquitoes are rare) and nearby Laupāhoehoe Forest Reserve (where mosquitoes are abundant).

This work is designed to provide managers with better mosquito monitoring tools so that mosquito eradication measures have the most impact. The research will also help managers design longer-term approaches to predict how locations and times of year of mosquito outbreaks will shift as climate conditions continue to change. While this work will be focused on the U.S. Fish and Wildlife Service Hakalau Forest National Wildlife Refuge and the Laupāhoehoe Forest Reserve the work will be applicable to other areas in Hawaiʻi with imperiled native forest bird populations.





Dennis LaPointe
Research Ecologist, USGS Pacific Island Ecosystems Research Center