In June, the skies over Hawaii's forests witnessed an unusual sight: drones releasing biodegradable capsules, each carrying about 1,000 specially bred male mosquitoes. These mosquitoes do not bite and have been intentionally designed for one purpose: to stop the spread of a disease that is devastating native bird populations.

These male mosquitoes, raised in the laboratory, carry a bacterium called Wolbachia. When they mate with wild female mosquitoes that do not carry the same strain, the resulting eggs do not hatch. This biological strategy is being deployed to combat the growing problem of mosquitoes in Hawaii, which is pushing native birds such as Hawaiian honeycreepers to the brink of extinction.

Hawaiian honeycreepers, brightly colored and uniquely adapted birds found only in Hawaii, are essential for pollination, seed dispersal, and play an important cultural role. Once numbering over 50 species, only 17 remain today, most of which are listed as endangered. One species, the Akikiki, was declared functionally extinct in the wild in 2023. Fewer than 100 individuals remain of another species, the ʻakekeʻe.

Although habitat loss has played a role, the most immediate and deadly threat is avian malaria, a disease transmitted by mosquitoes. Mosquitoes are not native to Hawaii; they were first introduced in 1826, likely by whalers. Since then, they have triggered multiple waves of bird extinctions: many native species had no natural resistance.

Historically, some birds have found refuge in the cooler, higher forests of islands like Maui and Kauai, where mosquitoes could not survive. But due to climate change, temperatures in these mountainous areas are rising, allowing mosquitoes to extend their range upwards. As a result, birds are being pushed higher and higher until there is nowhere left to go.

"If we don't interrupt this cycle," warns Dr. Chris Farmer of the American Bird Conservancy (ABC), "we are going to lose our Hawaiian honeycreepers."

To avoid this outcome, conservationists have been working for years to find a safe and effective way to reduce mosquito numbers without harming Hawaii's delicate ecosystem. Pesticides are not ideal: they could also kill beneficial native insects like fruit flies and damselflies.

The solution they have chosen is called the Incompatible Insect Technique (IIT). It has been studied for decades, particularly as a method of controlling mosquitoes that transmit diseases like malaria, Zika, and dengue. In IIT, male mosquitoes raised in the laboratory with a specific strain of Wolbachia are released into the wild. When these males mate with native females, the eggs do not hatch, reducing the mosquito population over time.

In 2016, the ABC and the conservation coalition "Birds, Not Mosquitoes" began working on applying IIT to Hawaii. As the mosquitoes that transmit avian malaria are different from those that transmit human diseases, scientists had to find the right strain of Wolbachia for the southern house mosquito in Hawaii.

After years of research, regulatory hurdles, and community outreach (people had legitimate concerns about releasing millions of mosquitoes), the project progressed. In 2022, the mosquitoes were being raised on a large scale in California. In 2023, releases began on Maui using helicopters to drop capsules into honeycreeper habitats.

"We estimate the number of wild mosquitoes and try to release ten times more lab mosquitoes," explains Farmer. "The idea is to overwhelm the population, so the females mostly mate with the sterile males."

Each week, 500,000 of these modified mosquitoes are released in Maui and Kauai.

The biggest challenge has been Hawaii's isolated and mountainous terrain, coupled with unpredictable weather. Helicopters are expensive and have limited availability, as they are also used for firefighting and tourism. Many missions had to be postponed at the last minute due to storms or wind.

This is where drones come in. After testing them in harsh conditions and equipping them with specialized containers that protect the mosquitoes in transit, the drones began making mosquito deliveries in June 2025. According to ABC's aerial deployment manager, Adam Knox, this is the first time in the world that mosquito capsules have been deployed by drone.

Drones offer better scheduling, reduced operating costs, and less environmental impact: no pilot is needed on board, and they produce fewer emissions and less noise.

Farmer estimates that it will take about a year before the team can determine whether the IIT technique is effectively reducing mosquito populations. The hope is that this will give the endangered birds enough breathing room to recover, or at least survive long enough for other long-term solutions to be developed.

A recent study by the San Diego Zoo Wildlife Alliance and the Smithsonian's National Zoo supports this hope, noting that even though time is running out, it is not too late to save species like the ʻakekeʻe, if action is taken now.

Christopher Kyriazis, a postdoctoral researcher and lead author of the study, emphasized the urgency: "If you wait even a few years, the window to save these birds shrinks dramatically."

Although the technique has never been used on this scale or for conservation purposes before, Kyriazis believes it could work. If mosquito populations decline, bird populations may be able to recover, regain genetic diversity, and potentially develop resistance to avian malaria. One species, the ʻamakihi, has already shown early signs of evolving some resistance.

However, Kyriazis warns that even if a useful genetic mutation emerged now, it is unlikely to spread quickly enough to save the birds without help.

Meanwhile, conservation groups are also preparing captive populations of critically endangered birds like the Akikiki for possible reintroduction, if their habitats become safer.

Farmer, who has been deeply involved in the project, says the process is both emotionally exhausting and deeply motivating. Watching extinction happen is heartbreaking, but the tools to stop it now exist.

"If we don't save these birds in this decade," he says, "they probably won't be here at all in the future. That's what motivates us: the possibility of making a real difference."