Assessing mosquito populations in Kauaʻi to help limit the spread of avian disease and inform the conservation of Hawaiian forest birds

A hiker steps off a boradwalk snaking through a swampy area
With a warmer climate, mosquitos are breeding more rapidly in places like the Alakai Swamp on Kauaʻi, posing increasing threat of passing along diseases like avian malaria to endangered bird species. (Photo: DLaPointe)

Hawaiian forest birds play important roles in many ecological processes.  For example, 61% of native flowering Hawaiian plant species are either bird pollinated or dispersed through ingestion by birds. However, native bird communities across Hawaiʻi continue to decline despite efforts to control predators and enhance habitat. These declines are, in part, due to the mosquito-borne avian pox and avian malaria.

Scientific forecasts of the impact of avian disease on native bird populations under various climate change scenarios predict severe declines and species extinctions in all remaining forest habitat within the next 50 years. While little can currently be done to mitigate the effects of climate change on disease vectors, recent innovations in mosquito suppression and eradication may provide new tools to control or eliminate disease vectors from forest bird habitat. State and federal biologists across Hawaiʻi have made mosquito control a conservation priority and are currently focusing on developing the Wolbachia-based Incompatible Insect Technique (IIT) to suppress mosquito populations. This technique involves using naturally-occurring strains of the bacteria Wolbachia to cause mosquito incompatibility (where mosquito sperm and eggs are unable to form viable offspring) and infertility. Sustained releases of male mosquitoes infected with incompatible Wolbachia can help to suppress wild mosquito populations.

To meet regulatory approval for the use of Wolbachia and achieve successful suppression of mosquitos, key ecological parameters (population density, dispersal, and survivorship of the mosquitos) need to first be assessed. These parameters help to inform the number of Wolbachia-infected mosquitos to release as well as the location and timing of their release. This project will use Mark-release-recapture (MRR) techniques to gather information about mosquito populations in selected areas in Hawai’i. The MRR process includes capturing, marking, and releasing a portion of the population, and then later, capturing another portion and counting the number of marked individuals within the sample. This sampling will both improve the ability to detect and monitor mosquito populations and inform the use of IIT in the future for suppressing mosquitos. Results from this project will be directly useful to the conservation efforts of the U.S. Fish and Wildlife Service, the Pacific Islands Fish and Wildlife Office, and other resource management groups in Hawaiʻi.





Dennis LaPointe
Research Ecologist, USGS Pacific Island Ecosystems Research Center