Colillas de Cigarro Repelen Pestes

 City-dwelling sparrows and finches incorporate the butts of smoked cigarettes into their nests, seemingly to ward off parasitic mites.

 Isabel López-Rull and her colleagues at the National Autonomous University of Mexico in Mexico City found that nests of house sparrows (Passer domesticus) and house finches (Carpodacus mexicanus; pictured) with higher levels of cellulose acetate, a component of cigarette butts, had fewer mites. The researchers attached fibres from either smoked or unsmoked cigarette filters to parasite-attracting heat traps and placed them in 27 sparrow and 28 finch nests. Traps bearing fibres from smoked filters, which contain more nicotine than those of unsmoked ones, captured fewer mites, suggesting that nicotine — and perhaps other compounds in cigarettes — repel the parasites.
Birds have long been known to line their nests with vegetation that deters parasites, and the authors suggest that the use of cigarette butts is an urbanized form of this earlier adaptation.

Research Highlights Nature 492, 156 (13 December 2012)