(New Scientist) It's not just people that have a penchant for cigarettes. Birds living in urban environments often use cigarette butts to line their nests. Unlike in humans, the cigarettes seem to have a beneficial effect – they cut the number of parasites in the nests.
Nicotine-based sprays are already used on some crops to repel insects. To see whether cigarette butts might have a similar effect in urban birds' nests, Constantino Macías Garcia from the National Autonomous University of Mexico in Mexico City and colleagues lured parasites to these nests.