Pesticides are often considered dangerous to birds, but finches on the Galapagos Islands are now learning to use these human-made chemicals to their advantage. In an effort to help the finches deal with invasive flies that terrorize their nests, biologists with the University of Utah have set out pesticide-soaked cotton balls, which the birds are now using as part of their nests, reports Phys.org.

This might be the first instance of birds using human-made pesticides to "self-fumigate" their homes. The method has so far been effective in ridding finch nests of the blood-sucking maggots of the invasive nest fly Philornis downsi, which may have been accidentally introduced to the Galapagos Islands via ships and boats from the mainland sometime in the 1990s.

"We are trying to help birds help themselves," said biology professor Dale Clayton, senior author of the study.

The pesticide being used, permethrin, is considered harmless to finches. In fact, it's the same stuff used in head-lice shampoo administered to children.

"Permethrin is safe. No toxicologist is going to argue with that. The more interesting question is whether the flies will evolve resistance, as human head lice have done," explained Clayton.

The idea of baiting the birds with the pesticide-soaked cotton balls came from Clayton's colleague, Sarah Knutie, who noticed that several species of Darwin's finches would regularly grab frayed fibers from her laundry line to build their nests with. The cotton balls make for a superior substitute, and the birds probably notice that the cotton also prevents maggot infestation.

Since being introduced, maggots from the nest fly have infested the nests of virtually all land birds on the islands, including most of the 14 species of Darwin's finches, two of which are highly endangered. Past studies found that in some years the blood-sucking maggots kill all the nestlings in nests they parasitize, so they represent a serious threat to the biota of the sensitive Galapagos habitat.

Early results from the project show positive signs. All of the nests with the treated balls showed a significant reduction of the parasitic maggots. Researchers are also careful to only place cotton ball dispensers in areas frequented by endangered birds to prevent the pesticide from becoming too widespread and harming other aspects of the Galapagos ecosystem. By limiting the area of the study, researchers also hope to prevent the flies from developing a resistance to the pesticide.

If results continue to be positive, the method could be used to help other species facing similar perils elsewhere. For instance, Hawaiian honeycreepers are dealing with feather lice infestations, birds in Puerto Rico are often afflicted by Philornis flies, and the endangered Florida scrub jay is threatened by back fleas.

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