KILAUEA, Kauai — The future is bleak for Kauai’s last surviving native forest birds, researchers have long known.

But until recently, there was reason to hope that the decline of the akikiki — a tiny, imperiled honeycreeper with an estimated population size of fewer than 500 birds — had somewhat slowed when conservationists counted approximately the same number of birds in the high-elevation forest that is the species’ last frontier in both 2012 and 2018. 

“It made it look like …. maybe things weren’t quite so bad for the birds,” said Lisa Crampton, coordinator of the Kauai Forest Birds Recovery Project

This year the bubble of hope burst, however, when the number of akikiki breeding pairs located by conservationists numbered just three, compared to 35 pairs spotted by researchers four years ago.

In the last half-century, disease-carrying mosquitoes helped wipe out several Hawaiian forest bird species. Now the problem is accelerating. Courtesy: Leon Berard/2021

The new data suggests the species population may be smaller, and declining faster, than previously thought. 

“As scientists we’re supposed to be dispassionate, but they are our friends,” Crampton said during a virtual event geared at raising awareness of the birds’ dismal plight.

“It’s like you’re a nurse,” she said. “You’ve been taking care of these birds, trying to do everything you can for them and … you walk into your ward the next morning and they’re gone.”

Found only on Kauai, akikiki once inhabited forests from sea level to summit. Today the species is confined to the Alakai Plateau, where, historically, the climate at around 4,000 feet elevation was too cold for disease-carrying mosquitoes to thrive.

As the planet has warmed, however, mosquitoes have invaded new terrain, including the birds’ last refuge on Kauai. Increasingly, the birds are dying after being bitten by mosquitoes carrying a disease to which they are defenseless.

It’s a problem that started seasonally. But the climate has changed so much that now mosquitoes persist in the Alakai region year-round.

“The mosquitoes are taking over where we once had birds,” Crampton said. “We are really sounding the alarm bells at this moment in time for some of our most imperiled forest bird species.”

Of the eight forest bird species on Kauai, three are listed as endangered, one is threatened and three are in decline.

It’s not just a problem for Kauai’s forest birds, although the Garden Isle’s forested mountaintops are at a lower elevation than those on other islands and so the most dramatic effects of a mosquito invasion are being felt here first.

Only 17 forest bird species are left in Hawaii, down from more than 50 that evolved here over thousands of years, according to the Audubon Society. Hawaii’s surviving forest birds face numerous threats — deforestation, non-native predators such as cats and rats — but today the biggest one is avian malaria. 

Birth Control For Mosquitoes

In 2015, conservationists began collecting akikiki eggs from Kauai’s mountaintop forests and transporting them to the San Diego Zoo Wildlife Alliance, where there is now a captive flock of 41 akikiki — a sort of insurance policy against the species’ extinction. 

A lot of effort has been put into establishing a captive flock to help preserve the species in the long-term, even after akikiki die off in the wild. But the captive birds have so far produced only three offspring, raising concerns that the project may not work.  

Welsh artist Ralph Steadman depicted this mosquito as part of an effort to raise awareness for endangered species. Courtesy: Ralph Steadman

Absent the future development of a vaccine that would protect the birds from avian malaria, many scientists say the most effective intervention would be to control mosquito populations in the birds’ habitat by inhibiting their ability to produce fertile offspring. 

To do this, scientists would need to collect wild Southern house mosquitoes from the forests where the birds live and infect them with a bacteria called Wolbachia found in the reproductive tract of most insects. 

Scientists are finding that if they drain the Southern house mosquito of its natural bacteria strain and infect it with a different strain sourced from another species of Hawaii mosquito, they’ll achieve a form of mosquito birth control.

Scientists would then release into the wild a large batch of these male mosquitoes, which are infected with the different Wolbachia strain, to mate with wild females. The distinction in bacteria strains between the males and females would render their offspring sterile.

Since female mosquitoes mate only once, this incompatibility would send the wild mosquito population plummeting, achieving some relief for the birds.

And since male mosquitoes don’t bite, there would be no risk to the birds (and no added nuisance for humans) by releasing the batch of male mosquitoes into the birds’ mountaintop habitat.

The Race Is On

A multi-disciplinary group of scientists set out in 2019 to explore what it would take to make an historic effort at landscape-scale mosquito control in Hawaii a reality. 

Although the Wolbachia method of mosquito population suppression has worked as a public health tool to reduce the prevalence of human malaria elsewhere in the world, it has never been used as a conservation tool nor with the mosquito species that’s spreading deadly bird diseases in Hawaii.

The project is still in the planning and feasibility stages, according to Teya Penniman, coordinator of the multi-agency partnership Birds Not Mosquitoes

Akikiki spend much of their lives traveling in pairs or in groups through the forest, circling tree branches like a trapeze artist while coaxing bugs out of bark and clumps of moss. Courtesy: Kauai Forest Birds Recovery Project

The next step would be for the group to submit applications to the Environmental Protection Agency and the Hawaii Department of Agriculture for permits required to pioneer this emerging science on a landscape scale. 

In these approvals are won, the group anticipates they might be able to release into the wild a first batch of male mosquitoes that have been infected with the Wolbachia strain sometime in 2024 with expanded releases in 2025.

But extinction threatens to obliterate some forest bird species without swifter action, conservationists say. The akikiki, for example, may not persist beyond this decade, Crampton said.

So Penniman said the group is considering applying to the EPA for an emergency exemption that could speed up the regulatory approval process. 

“What we’re hearing from our friends and colleagues in the forest is, ‘That’s not fast enough. We’re going to lose species if it takes that long,’” Penniman said. “So we are really looking at what it will take to ramp that process up as much as we can.”

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