16-06-2025
Drones drop mosquitoes over Maui to save honeycreepers
Conservationists working to save Hawaii's endangered, native birds are now using drones to deliver lab-reared, male mosquitoes over Maui.
The male mosquitoes have a special purpose—to mate with wild females in the forests while carrying a naturally occurring bacteria that results in sterile eggs, thereby breaking the breeding cycle and reducing the population.
Scientists hope this 'incompatible insect technique ' will reduce the overall mosquito population in order to combat avian malaria, the primary cause of decline in Hawaiian honeycreeper species. Over time, they hope these native bird populations will then have a chance to recover.
'Reducing invasive mosquito populations is absolutely critical in preventing the extinction of Hawaii's vulnerable honeycreepers, ' said Chris Farmer, the American Bird Conservancy's Hawaii Director, in a statement. 'We have the technology to break the avian disease cycle in Hawaii, and a fighting chance to restore populations.'
He called the drone deployment a milestone, saying he expects the new technology to expedite the delivery of millions of mosquitoes, with more flexibility.
The first drones were deployed over Maui in April, according to drone pilot Adam Knox, after some engineering to figure out the best way to release them over the remote terrain.
Knox is testing out three different types of drones for the release of the mosquitoes, which are released inside of cone-shaped pods made of biodegradable paper pulp. Each pod contains about 1, 000 mosquitoes.
These pods are placed inside of a special transport box attached to the drone—sort of like a cooler—that keeps the pods at a controlled temperature due to the sensitivities of the male mosquitoes. Several pods are released at a time.
In order to release the pods, Knox, ABC's aerial deployment of mosquitoes project manager, had to work with his team to figure out a release mechanism that would work over mountainous terrain with significant elevation changes, strong winds, frequent rains, and mist.
The drops have to be consistent while flying over thousands of acres despite these challenges.
Knox said the test flights have shown it can be done by drone, which can be more flexible than manual drops via helicopter, without risks to humans on aerial flights.
It is the first known instance of specialized mosquito pods being dropped by drones.
'There is a whole new world out there in terms of utility with this tool, ' Knox said. 'This opens up a lot of possibilities now and into the future.'
Knox expects to continue refining the process, and to test out the drones over Kauai as well, in the near future. Manual drops via contracted helicopters, meanwhile, have been ongoing since November 2023, twice a week, and will continue.
Conservationists are racing to save several Hawaiian birds—specifically native honeycreepers—on the brink of extinction.
Last summer the akikiki on Kauai was declared, meaning only a handful were left in the wild and that the species could not sustain itself in the wild. Some akikiki, however, are being raised in captivity by the San Diego Zoo Wildlife Alliance.
Scientists believe if no action is taken, mosquitoes could cause other Hawaiian bird species to quickly decline and vanish.
Farmer said at least 33 species of honeycreeper are now extinct, and many of the 17 that remain, including the kiwikiu and akohekohe on Maui, and the akekee on Kauai, are highly endangered.
The kiwikiu, or Maui parrotbill, found on the slopes of Haleakala, have a population of less than 150 individuals. The akohekohe, or crested honeycreeper, also found in the high-elevation forests of Haleakala, have a population of fewer than 2, 000.
Due to climate change, mosquitoes have begun to move to higher elevations than in past years, he said, encroaching on the last remaining refuges available to surviving honeycreepers.
The birds are facing numerous obstacles to survival, including habitat loss and degradation due to grazing by hoofed animals, along with invasive predators such as rats that prey on their eggs and chicks.
The No. 1 drivers of the extinction crisis are believed to be mosquito-borne diseases such as avian malaria and avian pox. Scientists say a single bite from an infected mosquito could be fatal to a honeycreeper.
Reducing mosquitoes After years of study and analysis—and a—a multi-agency group made up of ABC, the U.S. Fish and Wildlife Service, Hawaii Department of Land and Natural Resources and others, embarked on the mosquito suppression project.
Collectively, the group calls itself Birds, Not Mosquitoes, and it has stood strongly behind the mission to reduce the invasive southern house mosquito population in high-elevation forests across the state to stem avian malaria.
The male southern house mosquitoes do not bite or transmit diseases, according to experts, but carry a certain strain of Wolbachia bacteria which results in unhatched eggs.
The project was opposed by Hawaii Unites, a nonprofit community group, that in 2023 to stop the multi-agency group from continuing the project.
Hawaii Unites, founded by president Tina Lia, expressed concerns about releasing any 'biopesticide lab-reared Wolbachia-bacteria-infected mosquitoes ' on the fragile ecoystems of Halaekala National Park or Hawaii's other forest reserves.
The group was concerned about unforeseen consequences of releasing the lab-reared mosquitoes.
Both the state Board of Land and Natural Resources and National Park Service had approved a 300-page environment assessment and finding of no significant impact for the project.
Hawaii Unites said a more comprehensive environmental impact statement was needed.
But a state Environmental Court ruled the project could go forward—and following an appeal by Hawaii Unites arguing that the EA did not have enough science and documentation to back its claims of being safe for the environment—an appeals court in April.
Birds, Not Mosquitoes prevailed in obtaining regulatory approvals to move forward on its conservation plan.
Conservation drones It is not the first time drones have been deployed to combat invasive species in Hawaii.
DLNR has shared in recent years that it used drones to drop citric acid over parts of Oahu, including Waimanalo and Kuliouou, in order to help control invasive coqui frog populations.
The deployment of mosquitoes with Wolbachia also has been used in the past in Texas and California, as well as Mexico, Singapore, Thailand and Australia to reduce mosquito-born diseases such as dengue, Zika and Chikungunya.
The use of the incompatible insect technique to help reduce avian malaria in Hawaii, however, is a novel one.
Farmer likes to describe the process as a sort of 'invisible barrier to protect our birds high up in the forests.'
While predator-proof fencing has been erected at refuges and forests to protect birds and ohia trees, this introduction of sterilizing male mosquitoes forms a sort of 'mosquito-proof fence.'
Conservationists believe their mission is time-critical, and that the project must move forward quickly. They are hopeful, but say it will take time to determine how effective this technique is in saving Hawaii's native honeycreepers.
'It takes time to knock them (invasive mosquitoes ) down and to reduce the population, ' Farmer said. 'We're monitoring and analyzing data. As soon as we can tell one way or another, we'll certainly let the public know.'
