I just read an interesting story that's worth sharing not only because of its relatively novel nature but also because it shows how rapidly animals can adapt to different situations and new challenges, in this case an urban environment.
Researchers Monserrat Suárez-Rodríguez, Isabel López-Rull, and Constantino Macías Garcia working out of the Departamento de Ecología Evolutiva at the Instituto de Ecología at the Universidad Nacional Autónoma de México, discovered that when house sparrows and house finches use cigarette butts to build nests this leads to a reduction of ectoparasites, bugs that live on the exterior of an organism (see also). In this study, 89% of house sparrow and 86% of house finch nests contained cigarette butt fibers.
Nicotine as a parasite repellent
The exact reason for the reduction in parasites isn't clear but it's thought that the nicotine that remains in smoked cigarettes functions as a parasite repellent. However, currently it's unknown if pesticides and other chemicals in the butts harm the birds, countering the effects of nicotine.
The amount of parasites is inversely related to the amount of butt material
In the discussion of their results the authors note "urbanization imposes new challenges on birds". I found this study to be very interesting because many animals are challenged by novel conditions in urban environments in which they have to share space with humans, and we need to know how the nonhumans adapt to their new homes because we are unrelentingly intruding into the homes of other animals. This study offers some intriguing suggestions.
Butts can also be extremely harmful
Before we extol the presence and virtues of cigarette butts and nicotine let's also keep in mind that butts tossed mindlessly or intentionally by humans cause incredible pollution and can harm animals. For example, 52.9 million cigarette butts were collected over "a period of 25 years during the International Coastal Cleanup, an annual event sponsored by the Ocean Conservancy. Consistently the number one piece of litter found, cigarette butts represent an astounding 32 percent of total debris items gathered overall at these cleanups. And that’s sadly not only the case on beaches but elsewhere too." Butts can cause animals to choke or starve to death. So butts are not a panacea.
The results of the study suggesting that cigarette butts may be helpful to birds should not be taken to mean that it's okay to throw them away willy-nilly. Surely, this is not what the authors intended and neither do these results offer a green light for smoking. This study does strongly suggest that there might be an upside to our wantonly polluting ways but I'd like to see people dispose of their butts in other ways. And, I'm sure most birds would agree.