Cigarette butts thrown from car windows along the roads or discarded all over the place in camp sites in game reserves have always been a minor irritation for me. Unlike plastic bags, tins & bottles they are too small for the anti-pollution enthusiast to pick up and dispose of correctly. Now evidence summarised in the journal Nature suggests that birds may appreciate smokers more than I do.
In 2002 researchers reported that, after laying their eggs, blue tits begin to gather plants such lavender, yarrow, curry, & mint to line their nests, & continue to do so until the chicks fly off. Many of the chemicals in these plants ward off bacteria, viruses, parasites, fungi and insects. This is analogous to the commercial mixtures e.g. citronella we buy to repel mosquitoes & flies. The birds select diverse plants on the basis of their chemical concentration & renew them regularly, stressing the role of olfaction in bird behavior. Perhaps the plants they use may reveal useful new safe insect repellents for human use.
Suárez-Rodríguez & her colleagues now report in Biology Letters that birds may similarly be using cigarette butts as a repellant. Nests which had a high content of cellulose, as a marker of cigarette content, had less parasites. Further tests showed that this correlated with the nicotine concentration i.e. nests with smoked cigarette butts repelled more parasites than nests with more unsmoked butts. The researchers do warn about the possible hazards of this adaptive behaviour i.e. carcinogenic effects on the fledglings.
I wonder if there is any evidence that heavy smokers are less often pestered by insects than non-smokers. We do use the smoke various candles based on plant oils as insect repellents. But perhaps any potential effect could also be directly related to chemical concentrations of nicotine in the blood
Petit, C., Hossaert-McKey, M., Perret, P., Blondel, J. & Lambrechts, M.M. Blue tits use selected plants and olfaction to maintain an aromatic environment for nestlings. Ecology Letters 5, 585 – 589 (2002).
Suárez-Rodríguez, M., López-Rull, I. & Garcia, C. M. Biol. Lett. http://dx.doi.org/10.1098/rsbl.2012.0931 (2012).