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Biologists try to beat the clock to save Maui’s endangered birds

Federal, state agencies seek to control mosquitoes that spread avian malaria

An i‘iwi perches on a mamane branch in Hosmer Grove in 2021. State and federal officials are proposing a project to suppress nonnative mosquitoes to help prevent avian malaria in Maui’s forest birds. A. BOONE / NATIONAL PARK SERVICE photos

A technique described as “mosquito birth control” is being proposed by federal and state conservation agencies as a way to prevent the extinction of Hawaii’s native forest birds as they fall victim to disease.

If the Hawaiian honeycreepers are to be saved, then “immediate action” needs to be taken to significantly reduce or eliminate nonnative mosquitoes that carry and spread avian malaria in East Maui, said Haleakala National Park superintendent Natalie Gates.

“We do not have time to wait on this,” Gates said during a virtual public meeting on Tuesday night.

Proposed by the National Park Service and the state Department of Land and Natural Resources, the project would use the “incompatible insect technique,” a mosquito suppression tactic that uses a common bacteria called wolbachia that affects their reproduction and ability to fertilize eggs.

“It’s the most promising tool we have to stop extinctions of our native forest birds,” DLNR entomologist Cynthia King said.

An amakihi takes a bite out of a pilo berry in Haleakala National Park in 2021.

There are only 17 of these species remaining statewide, including six on Maui. Of the six found in the Valley Isle, three are endangered: akohekohe, kiwikiu and i’iwi.

“The honeycreepers are found nowhere else in the world,” said Lainie Berry, forest bird recovery coordinator with DLNR. “Sadly, because of the increase in human activities, many of them have gone extinct. … If we don’t act fast, many of these species could go extinct in the next 10 years.”

While there are other threats to the Hawaiian honeycreepers — like predation, habitat loss, feral ungulates and competitive nonnative birds — disease, specifically malaria, is the most concerning, Berry said.

The southern house mosquito was introduced to Lahaina in 1826 and avian malaria followed soon after. This disease causes “rapid mortality” in honeycreepers, she said.

Some of the birds can die as quickly as nine days after being bit.

These mosquitoes cannot handle the cold, which is why they thrive in Hawaii’s climate.

Additionally, Berry said that increasing global temperatures and altered rainfall patterns are now allowing mosquitoes to travel to higher elevations where they once did not live, forcing forest birds to flock to even higher up.

“It’s threatening to wipe out the remaining honeycreepers in their last remaining safe habitat,” she added. “(East Maui) is where the forest birds are most critically endangered, so we wanted to address those areas first, but we do plan to widen the use of the tool to other areas.”

The mosquito birth control is being proposed to manage mosquito populations in a 100-square-mile project area in East Maui, which includes portions of the Hanawai Natural Area Reserve; Waikamoi Preserve; and the Hana, Makawao and Ko’olau Forest Reserves.

The technique involves giving mosquitoes the wolbachia bacteria, which can naturally live within the cells of insects and is found within 60 percent of insects worldwide. This bacteria cannot live in human cells, King said.

Only males will be used for the project. Males only feed on nectar and do not bite people.

“So if you flood a system with males that are incompatible because they have been given wolbachia, the likelihood is that only a small portion of those females will successfully find and reproduce with wild males,” King said. “So if you flood a system over multiple generations, you’re going to see a significant crash in mosquito populations.”

This tool has been used successfully worldwide for public health reasons to mitigate the spread of disease among people, she added.

If this project is approved for East Maui, however, this would be the first time that the incompatible insect technique has been used for conservation work to save endangered species, King said.

She’s hopeful that this tool will give them extensive results in about six months.

The treatment plan for conducting the proposed incompatible insect technique includes a release of mosquitoes at the “most effective” ratio of 20-to-1 about once a week to once per month at the project site area, said Chris Warren, National Park Service Forest Bird Program coordinator.

“You can’t just release as many mosquitoes as possible,” added Josh Fisher, invasive species biologist. “It costs money to produce those mosquitoes and you want to be efficient with your resources and use just what you need to make the tool effective.”

Incompatible male mosquitoes would be released through the help of “pedestrian ground crews” who will distribute the insects on foot, Warren said. Other methods include aerial release via helicopters dropping a long line down to the forest with an attachment that would release the insects, as well as through a drone release process, which has been effectively used for different species in the past.

While the goal is to reduce the number of mosquitoes at higher elevations within the project area, some incompatible males will be dispersed at lower elevations where they are breeding at greater numbers, Warren said.

Releases will likely be from May to October. The team would continue to monitor the technique and adjust the time, frequency and spacing.

“We aim to make this as efficient as possible as we learn how the mosquito populations are responding to those initial releases,” he said.

The project team is currently researching any anticipated impacts to other habits and species, health and human safety, visitor experience and cultural resources, and is open to any comments and suggestions that can be submitted online and via mail by Jan. 20.

Still, they do not anticipate any major disturbances and believe that a reduction in mosquitoes will only be to the birds’ benefit, Warren said.

Gates said there is some funding already secured from federal, state and nonprofit agencies to conduct this project if approved.

Up next, an environmental assessment will be prepared in the new year for the public to be able to review it by the summer of 2022. A final decision will be made on the proposal beginning September.

The next meeting will take place from 5:30 to 7 p.m. Jan. 6. To register, visit register.gotowebinar.com/register/7258589157911365390. The meeting will cover the same material as Tuesday.

For more information, visit parkplanning.nps.gov/HALE-mosquito. To submit a comment on the project, click the “open for comment” link, select “public scoping newsletter” and click the “comment on document” button to enter and submit. Comments can also be mailed to Superintendent, Haleakala National Park, P.O. Box 369, Makawao, HI 96768.

* Dakota Grossman can be reached at dgrossman@mauinews.com.

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