Darwin's famous finches are under threat from a parasite introduced to the Galapagos Islands that is now killing the birds' nestlings.

In research published Monday in the journal Current Biology, researchers detailed how they used pesticide-infused cotton to help eradicate the deadly flies, Reuters reported.

The scientists treated balls of cotton with permethrin, a mild pesticide used for head lice in people, and then placed them close to where the birds were constructing their nests.

The simple but effective idea, which served to kill at least half of the fly maggots in the finches' nests, came from University of Utah biology doctoral student Sarah Knutie.

"In 2010, I was sitting on my porch at the Charles Darwin Research Station and noticed Darwin's finches continuously landing on our laundry line. The birds were pulling frayed cotton fibers from the line and presumably taking them back to incorporate into their nests," Knutie told Reuters.

"Since we know that permethrin is effective at killing the parasite, I wondered if Darwin's finches could be encouraged to take cotton balls treated with permethrin back to their nests to kill the parasite," she said.

Working near nests on the Galapagos' Santa Cruz Island, the researchers discovered that all four species of finches in the area were inclined to use cotton, whether it was untouched or treated with the pesticide.

The flies of the species Philornis downsi were likely brought to the islands by people and are believed to be the cause of diminished finch populations. Named after the famous naturalist, Darwin's finches comprise 14 species of finch that inhabit the Galapagos Islands.

Scientists say the finches haven't yet evolved in reaction to the invasive parasites, making the research especially important to the endangered mangrove finch and medium tree finch species.

"This parasite is not historically found in the Galapagos Islands and, therefore, Darwin's finches have not had enough time to evolve defenses against the parasites," said University of Utah biology professor Dale Clayton, one of the researchers, as quoted by Reuters.

"In some years, 100 percent of nestlings die as a direct result of the parasites. It is critical to find a way to control the parasites in order to help the birds," Clayton said.

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