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Speaker 1: Welcome to brain stuff from how stuff works, Hey, brain stuff,

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Speaker 1: Lauren Bogelbaum. Here, the house sparrows and finches of Mexico

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Speaker 1: City may be proud to be called bird brains, and

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Speaker 1: why not. They figured out how to use one of

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Speaker 1: the grossest things on Earth, cigarette butts, to repel two

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Speaker 1: of the other grossest things on Earth, ticks and mites.

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Speaker 1: MoMA birds find their nests under constant and pervasive threat

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Speaker 1: from these blood sucking, feather feasting ectoparasites. Country birds have

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Speaker 1: easy access to nature's bountiful nest making materials, including certain

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Speaker 1: insect repelling herbs and plants. City dwelling birds, on the

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Speaker 1: other hand, face a concrete and steel urban landscape and

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Speaker 1: must curate their nests from a more anthropogenic or man

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Speaker 1: made palette enter cigarette butts. A study published in twelve

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Speaker 1: in the journal Biology Letters details the ongoing investigation of

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Speaker 1: an urban population of breeding house finches and house sparrows

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Speaker 1: at the National University of Mexico in Mexico City. The

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Speaker 1: author's found that both species interweaved anywhere from a few

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Speaker 1: to a few dozen smoked cigarette butts into their twiggy

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Speaker 1: eclectic domiciles. In fact, the study concluded, the more butts,

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Speaker 1: the healthier the nest. Nicotine is an insecticide generated by

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Speaker 1: the tobacco plant to ward off invasive leaf eating arthropods

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Speaker 1: like beetles. Some residual nicotine remains in the fibers of

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Speaker 1: cigarette butts that motherbirds used to line and insulate their nests.

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Speaker 1: It turns out that this nicotine tinged filter fluff has

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Speaker 1: medicinal and pesticidal properties that repel tis, in particular, protecting

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Speaker 1: MoMA's chicks from a potentially lethal fate. Overall, the study

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Speaker 1: concludes that the more cigarette filter fiber there is in

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Speaker 1: the nest, the fewer ticks and mites, revealing persuasive evidence

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Speaker 1: that parasites don't like cigarette butts and that nests built

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Speaker 1: with these butts attract fewer parasites. But there's no Avian

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Speaker 1: surgeon general, so who decides whether this seemingly beneficial cigarette

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Speaker 1: habit harms the birds or is a savvy and resourceful

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Speaker 1: example of urban wildlife adaptation. Researchers confirmed that there is

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Speaker 1: some genetic damage linked to the activity, but they believe

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Speaker 1: that the positive life saving anti parasitic effects far outwaigh

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Speaker 1: any long term negative consequences. So you've come a long

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Speaker 1: way Bertie's, and you're helping clean up our cities while

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Speaker 1: you're at it. Interestingly, there's another way that birds may

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Speaker 1: help combat cigarette but litter. A Dutch startup Crowded Cities

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Speaker 1: is developing the Crowbar and Autonomous training device to teach crows,

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Speaker 1: some of the most competent scavengers in the world, to

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Speaker 1: deliver found cigarette butts to a trash receptacle in exchange

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Speaker 1: for food reward. Today's episode was written by Carrie Tato

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Speaker 1: and produced by Tyler Clang, with kind engineering assistance by

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Speaker 1: Ramsey yungt. For more on this and lots of other

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Speaker 1: bird brained topics, by which we obviously mean clever and helpful,

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Speaker 1: visit our home planet, how stuff Works dot com.