We all know by now that smoking is bad for us (even though a lot of people still smoke). But cigarette butts may provide a benefit to urban birds, which use the butts to build their nests.
Urban animals are forced to make new adaptations to their surroundings. One issue that city birds must deal with is parasite infection in their nests. Parasites can cause disease or death in birds, by sucking the bird’s blood or spreading infections. Cigarette butts, it turns out, can help birds fend off these parasites, according to a study published December 5 in Biology Letters.
Three researchers from the National University of Mexico found that house sparrows and finches living in Mexico City used discarded cigarette butts to line their nests. In addition, they found that the more cigarette butts were in the nests reduced the number of parasites. According to the researchers, between 10 and 15 grams of cigarette butt material reduced the number of parasites to nearly zero.
Why build with cigarette butts? Nicotine may be the answer, the researchers found. Nicotine is a powerful anti-herbivore molecule that is still present in a butt even after the cigarette is smoked. What is not clear, however, is whether the birds know this when gathering nesting materials. Sparrows and finches are known to build nests using green plant materials (thin sprigs and leaves), and the cellulose from smoked cigarettes could be just another type of green plant materials, from the bird’s perspective.
And since it’s pretty difficult to obtain the bird’s perspective, knowing why the birds build with butts presents a significant challenge.
Source: Biology Letters