An experimental demonstration that house finches add cigarette butts in response to ectoparasites

Journal of Avian Biology Authors First published: August 2017 DOI: 10.1111/jav.01324 Abstract Urban species encounter resources that are uncommon in nature, such as materials found in city waste. Many studies have shown that these can be harmful to wildlife. In Mexico City, house finches bring cigarette butts to their nests, which reduces the amount of ectoparasites, but also induces genotoxic damage in chicks and parents. Yet, the reason for this behaviour is unknown. One possibility is that birds extract the cellulose fibres from discarded butts simply because they resemble feathers. Alternatively, disassembled cigarette butts may be brought to the nests because they repel ectoparasites. Here we tested the latter hypothesis by assessing whether house finches Carpodacus mexicanus increase the amount of cigarette butts in their nests in response to a raise in ectoparasite load. When present, fibres from butts are concentrated in the nest lining. By taking it away, we simultaneously removed most of the butt material and collected the bulk of the tick population infesting each nest, as these parasites cluster in the lining. We removed the bedding of nests when chicks had recently hatched, and randomly assigned each nests to one of the following treatments: 1) addition of live ticks, 2) addition of dead ticks and 3) simulation of tick addition. Females in the live ticks’ treatment added more butt fibres to their nests than parents in control treatments. Additionally, the amount of butt fibres in the original lining also predicted the amount of fibres added after the manipulation. It seems that the tendency to bring to the nest cigarette butts is at least partially a response to current, and perhaps also past, parasite load. Birds and the City Posted on April 3, 2017 by Frontiers Communications in Infographics, Science // 0 Comments Songbirds’ innovative behavioral adaptation in urban environments has fitness costs and benefits. Cities are environments which bring humans and wildlife into close contact, where both parties must adjust their behavior to accommodate the activities of the other. Understanding how wildlife responds and adapts to human activity is important in a world of increasing urbanization. In Mexico City, Monserrat Suárez-Rodríguez et. al. studied a curious behavioral adaptation in common sparrows and finches, published in Frontiers in Ecology and Evolution as part of a Research Topic on behavioral and ecological consequences of urban life in birds. These two songbird species have been observed lining their nests with cigarette butts; this habit has interesting benefits, but dangerous consequences as well. The infographic below provides an outline of their experiment and results. Read the full study in Frontiers in Ecology and Evolution here. CigaretteBirds.jpg Infographic also available as PDF: CigaretteBirds https://blog.frontiersin.org/2017/04/03/birds-and-the-city/