Bird Nabs Human-Made Pesticide to Kill Maggots

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Wild finches in the Galapagos Islands "self-fumigate" by using a human-made pesticide to kill parasitic fly maggots, a study in the latest issue of Current Biology reports.

Birds, like the rest of us, like to be the boss. Instead of treating maggot-infested nests directly, biologists are setting out pesticide-treated cotton balls, which finches are grabbing as material for building nests.

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It's helping to rid nests of maggots, which may feed on the blood of baby birds, sometimes leading to their deaths.

The pesticide, permethrin, is safe for the birds, according to senior author Dale Clayton, a University of Utah biology professor.

"It might kill a few other insects in the nest," Clayton said in a press release. "This is the same stuff in head-lice shampoo you put on your kid. 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."

A colleague of Clayton's, Sarah Knutie, came up with the clever idea while studying animals in the Galapagos Islands. The finches here are related to Charles Darwin’s famous finches, which helped the renowned British naturalist to formulate the theory of evolution after he observed incredible diversity among the birds.

Knutie noticed that the finches "were coming to my laundry line, grabbing frayed fibers from the line and taking it away, presumably back to their nests." (The industrious birds were also collecting toilet paper, as well as string and fibers from towels.)

Knutie and her team built wire-mesh dispensers, filling them with cotton balls treated with 1 percent permethrin solution. At least four species of Darwin’s finches grabbed the balls and incorporated them into their nests.

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All of the nests with the treated balls showed a significant reduction of the parasitic maggots. Effectiveness depended upon the number of cotton balls. Just a thimbleful of treated cotton can kill 100 percent of the destructive fly larvae.

"We are trying to help birds help themselves," Clayton explained. "Self-fumigation is important because there currently are no other methods to control this parasite."

The researchers think that other species might benefit from self-fumigation too. They mention that Hawaiian honeycreepers are suffering now from feather lice, while flies terrorize birds in Puerto Rico. The endangered Florida scrub jay is fighting back fleas.

Self-fumigation isn't just for the birds either. In the future, the same method might be used on the black-tailed prairie dog, whose populations have been declining in the Great Plains due to fleas infected with plague bacteria.

Photo: A finch in Ecuador's Galapagos Islands pulls a cotton ball from a dispenser set out by scientists. Credit: Sarah Knutie, University of Utah.

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