Birds Have Figured Out That Cigarettes Are Good for Them

Researchers have known for years that some birds use discarded cigarette butts to build nests. A new study has compiled evidence to show what’s behind this behavior: the butts keep parasites at bay.

The butt-building behavior has been observed all over the world. Darwin’s finches in the Galápagos, house finches in Mexico, and song thrushes in New Zealand are all lining their nests with butts. Some songbirds in Britain are even known to go right to the source by making their nests in outdoor ashtrays.

Now researchers at the University of Lodz in Poland have compiled data on  the butt-nesting under laboratory conditions. They looked specifically at  blue tits, which are found across Europe, in the urban forest areas near the university. Their findings appear in the journal Animal Behaviour.

The team monitored 99 birds nesting in three different nest boxes: one using sterilized moss and cotton wool; one that included two cigarette butts in the nest; and a third untouched and natural, as a control.

A few days after chicks hatched, the babies were measured and blood samples drawn. The researchers found that nestlings in the sterile nests, as well as the broods in the butt-lined boxes, were healthier than those in the control group.

Once the babies flew the coops, the researchers analyzed parasite populations in the nesting materials. As expected, the untouched natural nests had the most parasites and the sterilized nests had none. The butt nests had fewer parasites (especially blowflies and fleas) than in the natural nests. Just two butts per nest made a measurable difference.

It’s the chemical compounds in cigarette butts (there are about 4,000 of them) that ward off the parasites. Whether it’s the nicotine, arsenic, heavy metals, or some other compound, something in cigarettes is bad for bugs and good for birds. The interesting thing is that birds have figured that out somehow.

Photo credit: perplexity.ai