In an effort to save endangered native forest birds, the multi-agency partnership Birds, Not Mosquitoes has been releasing sterile male mosquitoes on Maui.
The method, known as the "incompatible insect technique,” aims to reduce the numbers of disease-spreading, non-native southern house mosquitoes.
Avian malaria, spread by mosquitoes, is the number one threat to the endemic Hawaiian honeycreepers. Researchers say mosquito control is one of the last best options to save the birds.
Birds, Not Mosquitoes releases 500,000 male mosquitos a week via helicopter drops — and recently hit the 14 million mark. Unlike female mosquitoes, male mosquitoes don't bite, so they can't transmit diseases.
"Their main function is to go out and mate with wild females, and when they mate with wild females, the eggs that she lays won't hatch, and that results in an overall reduction in the number of new mosquitoes and thus the population of mosquitoes that are in the area being treated," said Christa Seidl of the Maui Forest Bird Recovery Project.
She said the team deploys the mosquitoes in specific permitted areas in East Maui.
"We have locations that we've identified that have mosquito populations but are also adjacent to endangered forest bird habitat that ideally we can reduce the number of mosquitoes in those locations, so that benefits the birds that are upslope."
Researchers monitor the mosquitoes by checking various carbon dioxide traps in the field. A team collects the trapped mosquitoes and identifies them by species and sex.
"We use that data over time between areas we treat and comparable areas we are not treating, so known as control sites, and we look at differences over time in the catch rates. And if we see significant differences that persist in those catch rates over time, we have stronger evidence that the mosquitoes are being suppressed in the locations we're deploying pods," Seidl said.
Scientists also hope to use drones alongside or in place of helicopters, which require good weather windows — not to mention pilot scheduling.
"With a drone operating internally, we can pretty much operate on demand when conditions are best," said Adam Knox of the American Bird Conservancy. "Also there's lower impacts in terms of emission and just environmental impacts."
The conservancy is working with vendors to custom-make the drones. Once testing is completed, the drones could replace helicopter drops at some suitable locations.
"Hawaiʻi was once an island of mostly birds, and we have an obligation, again it's our kuleana, to protect these species and allow them to persist here in Hawaiʻi," Seidl said.
A new documentary from Birds, Not Mosquitoes called “Vanishing Voices: Saving Our Hawaiian Forest Birds” is out now. Click here for showings.
This interview aired on The Conversation on Aug. 22, 2024. The Conversation airs weekdays at 11 a.m. on HPR-1. Tori DeJournett adapted this story for the web.
