Every week at the Maui airport, a small helicopter gets loaded with 250,000 passengers. They're male mosquitoes, key players in a strategy that could be the last, best hope for Hawaii's endangered birds.
"We got mosquitoes to drop," Christa Seidl of the calls to the pilot. She wheels over a crate with several hundred cardboard tubes filled with mosquitoes. Soon, they鈥檒l be airdropped into Maui's high-elevation forests, the last refuge for endangered birds.
There were once more than 50 species of Hawaiian honeycreepers, small colorful birds that filled the native forests and have important significance in Native Hawaiian culture. Now, those forests are going silent. Only 17 species of honeycreeper are left, with some expected to go extinct in the wild as soon as this year.
Honeycreepers are disappearing because of avian malaria, transmitted by mosquitoes that were introduced to Hawaii by accident in the 1800s. With no immunity, native birds often die after a single mosquito bite.
Still, small pockets of birds have endured because the mosquito onslaught has been halted by an invisible line. Above 4,000 to 5,000 feet in elevation, temperatures are too cold for mosquitoes, so the birds there have remained safe. But as temperatures rise with climate change, the mosquitoes are advancing into the birds' last remaining refuge.
As a last-ditch effort to save the birds, a coalition of groups, including the National Park Service, the state of Hawaii and nonprofits like the Maui Forest Bird Recovery Project, is borrowing a strategy from public health departments. Where mosquitoes spread human diseases, modified mosquitoes that are unable to reproduce successfully are often released, helping to suppress the overall mosquito population.
Now, this strategy is being used for wildlife conservation for the first time, according to the coalition, known as . It's a sign of the more aggressive level of intervention that humans are engaging in to stem biodiversity loss as the climate gets hotter. The question is whether it can effectively suppress the mosquito population in time to save the birds.
"We are in an ongoing extinction crisis," says Chris Warren, forest bird program coordinator at Haleakal膩 National Park in Maui. "The only thing more tragic than these things going extinct would be them going extinct and we didn't try to stop it."
Inside the bird ICU
Hawaii鈥檚 honeycreepers are found nowhere else on Earth and make up an integral part of the ecosystem. The birds help pollinate Hawaii鈥檚 native plants, eat insects and support the forest. Those forests also filter the rainfall that provides drinking water to many communities.
As honeycreepers have steadily disappeared, conservationists have made a difficult call. When it鈥檚 clear a bird will vanish, the remaining few are brought into captivity for safe-keeping at the Maui Bird Conservation Center, which is part of the San Diego Zoo Wildlife Alliance.
鈥淲e call our program an intensive care unit,鈥� says Jennifer Pribble, wildlife care supervisor at the center. 鈥淭his is the last resort.鈥�
The cluster of buildings in upcountry Maui is home to some of the rarest birds on the planet. There鈥檚 the 'alal膩, the Hawaiian crow, which is extinct in the wild. The calls of the chatty, intelligent birds can be heard echoing between the buildings.
There's also the 'akikiki, a pale gray bird that鈥檚 likely to go extinct on its home island of Kauai sometime this year. In a tall enclosure, the tiny birds hop from branch to branch.
鈥淔ifteen years ago, the population was over a thousand,鈥� Pribble says. 鈥淭oday there鈥檚 anywhere from two to five birds left in the wild.鈥�
Just over 40 'akikiki in captivity represent essentially the entire population of the species, which is split between the Maui bird center and a facility on another island. So every bird matters. When the Maui wildfires hit in August 2023, a fire began not far from the center. Pribble, who lives at the facility, realized at 3am that the flames were just across the road, spewing embers.
鈥淚 had fire extinguishers and garden hoses and put the fire out,鈥� she says. 鈥淭hat was a long night.鈥�
To grow the population of the rare birds, the center has a breeding program, carefully pairing birds to ensure their genetic health. Every year, three to four 'akikiki chicks are born. But the birds can't be released into the wild yet. The only place that's safe is inside these buildings, which are carefully wrapped in mosquito screens.
Forests going quiet
In a dense Maui forest, Christa Seidl is looking for honeycreepers. But there are few to be found.
鈥淏efore mosquitoes and before disease, this forest would be a cacophony of bird song,鈥� she says looking up. 鈥淭here would be huge flocks of 'i'iwi and 'apapane.鈥�
This forest has been heavily changed, like many of Maui鈥檚 remaining forests. Invasive plants like ginger choke out the native trees. Animals not native to Hawaii, like deer and rats, have moved in. And the forest has become eerily quiet as Hawaiian birds have disappeared.
Still, there are pockets of forests still filled with the sounds of native birds. At higher elevations, the southern house mosquito, which carries avian malaria, hasn鈥檛 been able to advance because temperatures were too cold. With climate change, that all changed.
鈥淚t鈥檚 increasing in temperature, and that鈥檚 allowing mosquitoes to creep increasingly upslope and now invade habitats that were once the last remaining refugia for a lot of our native birds,鈥� Seidl says.
Her team has watched it happen in real-time. One of the next honeycreepers headed toward extinction is the kiwikiu, a small yellow bird with a parrot-like beak. Today, there are only around 100 left in the wild. With most of Maui鈥檚 forests cut down for ranching and agriculture, the Maui Forest Bird Recovery Project began a lengthy effort to restore new habitat for the birds that was safe from mosquitoes. Over a decade, they planted tens of thousands of trees.
In 2019, 14 kiwikiu were released into the new reserve. Within weeks, almost all of them died. A spate of hot weather had allowed mosquitoes to move in, spreading avian malaria.
鈥淚t was really hard,鈥� says Hanna Mounce, program manager at the Maui Forest Bird Recovery Project. 鈥淲hen failure is extinction and we want to know we鈥檝e done every single thing that we possibly can, even if we do end up losing some of these species, it鈥檚 still incredibly difficult.鈥�
Making mosquito couples incompatible
After that, Seidl says the bird conservation community realized it needed to broaden its strategy. 鈥淲e realized there was no longer any running from the mosquitoes,鈥� she says. 鈥淚f we don't do anything, we will lose many of our native species.鈥�
So, they looked to mosquito-control efforts already going on around the globe. Since mosquitoes spread human diseases like dengue and Zika, public health programs have targeted them using new technology. One technique is to release mosquitoes that help to suppress the population because they can鈥檛 successfully mate.
The method, known as 鈥渋ncompatible insect technique,鈥� . Just like humans, insects also have bacteria living inside their bodies. One kind, known as Wolbachia, is already found in Maui mosquitoes and it alters their reproductive cells. When two insects both have the same strain of Wolbachia, they can successfully reproduce. But when a male and female have a different strain, their eggs don鈥檛 hatch.
鈥淭his technique has been used all over the world to reduce mosquito populations,鈥� Seidl says. 鈥淭hey鈥檝e used it successfully in China, Mexico. There鈥檚 programs ongoing in California, Florida.鈥�
So far, 10 million male mosquitoes have been given a different strain of Wolbachia and released by helicopter in high-elevation forests on Maui. Since females only mate once, mating with a modified male mosquito ensures they don鈥檛 have offspring, helping shrink the overall population.
鈥淲hat the previous studies have really shown is that this tool works, but the biggest issue with this is: can we apply the tool effectively enough to reduce the mosquito population?鈥� says Warren of the National Park Service.
Since mosquitoes only live a few weeks, the helicopter releases must be ongoing to keep the population down, often in locations that are difficult to access. The project will need continual funding, which so far has . It鈥檚 already from a group opposed to the releases. To measure its effectiveness, the team hopes to start seeing reduction in mosquito levels after the summer months, when mosquito populations typically boom.
A hope for immunity
With some honeycreeper species only having years left until extinction, time is running out for the strategy to work. Warren says it鈥檚 difficult to fully understand how biodiversity loss will affect an entire ecosystem.
鈥淔rom a biodiversity standpoint, I鈥檝e likened it to a Jenga stack,鈥� Warren says. 鈥淵ou keep pulling things out and you don鈥檛 see a big change. And then at some point you do, because at some point there鈥檚 so little left that it all comes tumbling down.鈥�
The disappearance of honeycreepers would also mean the loss of species found nowhere else.
鈥淥ur world will just become less colorful, less diverse as we continue to let species go extinct,鈥� Seidl says.
Ultimately, the hope is that Hawaii鈥檚 honeycreepers will develop immunity to avian malaria, as birds in other places have done. And there鈥檚 already been a sign it could be possible. Recently, , far from where he was released, having survived malaria.
鈥淚 don鈥檛 know how he did that,鈥� Mounce says. 鈥淏ut he not only survived malaria, he鈥檚 had a successful hatch and fledged a chick last year and has a female this year. He鈥檚 doing great. I don鈥檛 think we can rely on enough of them making it through on their own, but the fact that some of them can, they鈥檙e helping us.鈥�
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