Millions of mosquitoes released from helicopters in Hawaii to save rare birds

Millions of mosquitoes are being released from helicopters in Hawaii in a last-ditch effort to save the island's rare honeycreeper birds from extinction. The bright-colored honeycreepers, native to the archipelago, are succumbing to avian malaria, a disease carried by mosquitoes introduced by European and American ships in the 1800s. Lacking immunity to this disease, the birds can die after a single mosquito bite.

Thirty-three honeycreeper species have already gone extinct, and many of the remaining 17 are highly endangered. Conservationists warn that some species could disappear within a year if no intervention occurs. In a novel approach, conservationists are releasing male mosquitoes infected with a naturally occurring bacterium that acts as birth control. Helicopters are dropping 250,000 of these mosquitoes weekly, and so far, 10 million have been released.

“The only thing that’s more tragic is if [the birds] went extinct and we didn’t try. You can’t not try,” said Chris Warren, forest bird programme coordinator for Haleakala National Park on Maui. The Kaua'i creeper, or akikiki, exemplifies the urgency, with its population plummeting from 450 in 2018 to just five in 2023. Only one bird is known to survive in the wild on Kaua'i island, according to the National Park Service.

Honeycreepers play a crucial ecological role, pollinating plants and controlling insect populations. They are known for their canary-like songs and diverse beak shapes, adapted to various diets from snails to nectar. However, with no evolutionary history of avian malaria, species like the scarlet honeycreeper (‘i’iwi) have a 90% mortality rate if bitten by an infected mosquito.

Currently, honeycreepers inhabit high elevations (above 1,200-1,500 meters), where mosquitoes are absent due to cold temperatures. However, climate change is enabling mosquitoes to migrate to these higher elevations, posing new threats to the birds.

Researchers are employing the incompatible insect technique (IIT), where male mosquitoes are released with a Wolbachia bacterium. This bacterium prevents the eggs of wild females from hatching, effectively reducing the mosquito population over time. Female mosquitoes only mate once, making this method particularly effective.

The IIT method has previously reduced mosquito populations in China and Mexico, with ongoing projects in California and Florida. The effectiveness of the Hawaii program should become evident by summer, when mosquito populations typically surge. Dr. Nigel Beebe from the University of Queensland noted that islands are ideal for such eradication efforts due to limited re-migration.

The project, under the banner Birds, Not Mosquitoes, is led by a coalition including the US National Park Service, the state of Hawaii, and the Maui Forest Bird Recovery Project. Dr. Beebe emphasized that IIT is preferable to pesticides, which have broader ecological impacts, especially in conserving critical species. However, he acknowledged the long-term challenges of mosquito eradication, particularly on mainland areas.