City Birds Use Cigarette Butts as Bug Repellent

Birds everywhere add insect-repelling plants to their nests, but urban birds have to get a little creative. Learn how cigarette butts help city birds stay healthy in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:02):
Welcome to brain stuff from how stuff works, Hey, brain stuff,
Lauren Bogelbaum. Here, the house sparrows and finches of Mexico
City may be proud to be called bird brains, and
why not. They figured out how to use one of
the grossest things on Earth, cigarette butts, to repel two
of the other grossest things on Earth, ticks and mites.

(00:22):
MoMA birds find their nests under constant and pervasive threat
from these blood sucking, feather feasting ectoparasites. Country birds have
easy access to nature's bountiful nest making materials, including certain
insect repelling herbs and plants. City dwelling birds, on the
other hand, face a concrete and steel urban landscape and
must curate their nests from a more anthropogenic or man

(00:44):
made palette enter cigarette butts. A study published in twelve
in the journal Biology Letters details the ongoing investigation of
an urban population of breeding house finches and house sparrows
at the National University of Mexico in Mexico City. The
author's found that both species interweaved anywhere from a few
to a few dozen smoked cigarette butts into their twiggy

(01:06):
eclectic domiciles. In fact, the study concluded, the more butts,
the healthier the nest. Nicotine is an insecticide generated by
the tobacco plant to ward off invasive leaf eating arthropods
like beetles. Some residual nicotine remains in the fibers of
cigarette butts that motherbirds used to line and insulate their nests.
It turns out that this nicotine tinged filter fluff has

(01:28):
medicinal and pesticidal properties that repel tis, in particular, protecting
MoMA's chicks from a potentially lethal fate. Overall, the study
concludes that the more cigarette filter fiber there is in
the nest, the fewer ticks and mites, revealing persuasive evidence
that parasites don't like cigarette butts and that nests built
with these butts attract fewer parasites. But there's no Avian

(01:50):
surgeon general, so who decides whether this seemingly beneficial cigarette
habit harms the birds or is a savvy and resourceful
example of urban wildlife adaptation. Researchers confirmed that there is
some genetic damage linked to the activity, but they believe
that the positive life saving anti parasitic effects far outwaigh
any long term negative consequences. So you've come a long

(02:12):
way Bertie's, and you're helping clean up our cities while
you're at it. Interestingly, there's another way that birds may
help combat cigarette but litter. A Dutch startup Crowded Cities
is developing the Crowbar and Autonomous training device to teach crows,
some of the most competent scavengers in the world, to
deliver found cigarette butts to a trash receptacle in exchange

(02:32):
for food reward. Today's episode was written by Carrie Tato
and produced by Tyler Clang, with kind engineering assistance by
Ramsey yungt. For more on this and lots of other
bird brained topics, by which we obviously mean clever and helpful,
visit our home planet, how stuff Works dot com.