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Urban house finch (Carpodacus mexicanus) nest. Credit: JerryFriedman/CC BY-SA 4.0 |
Here is yet another fascinating example of the ingenuity of biological adaptability - and an example that should make any self-respecting intelligent design advocate cringe with embarrassment.
Constantino Macías Garcia at the National Autonomous University of Mexico, and his colleagues have been studying a curious phenomenon observed in the Mexican urban house finch (Carpodacus mexicanus) in which they collect cigarette butts and place then in their nests. There was inconclusive evidence that the effect was to deter parasitic ticks and other nest parasites so they designed a simple experiment to settle the matter. It was strongly suspected that nicotine and other chemicals in the butts acts as a deterrent to parasites. House sparrows (Paser domesticus) have also been observed to use the same strategy.
They observed 32 nests of C. mexicanus and one day after the eggs had hatched they removed the nest linings together with any parasites then they replaced the lining with an artificial felt one. They then added live ticks to 10 nests, dead ticks to another 10 and left the remaining 12 tick free.
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 (C. 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.
Suárez-Rodr-guez, M. and Garcia, C. M. (2017),
An experimental demonstration that house finches add cigarette butts in response to ectoparasites.
J Avian Biol. Accepted Author Manuscript. doi:10.1111/jav.01324 (pdf)
Copyright © 1999-2017 John Wiley & Sons, Inc. All Rights Reserved.
The results showed that the adults were significantly more likely to add cigarette butt material to nests with ticks and nests with live ticks had 40% more by weight of cigarette but fibres than those with dead ticks. These results strongly suggest that adult urban house finches have learned to use cigarette butts to 'medicate' their nests.
The same study however showed that the strategy is not risk-free. Examination of the red blood cells of chicks showed evidence of genetic damage interfering with cell division caused by nicotine. Either the benefits of the anti-parasitic effects are greater than the damage it causes or the effects manifest too late for the adults to respond to it.
Of course a study such as this can't tell us whether this is memetic or genetic evolution but however it arose, it self-evidently can't have arisen before there was a plentiful supply of cigarette butts so the behaviour is either of very recent origin or is an adaption of a preexisting strategy using other antiparasitic materials in the birds' environment.
Why this should make any self-respecting intelligent (sic) design advocate cringe and go into deep denial mode is because an intellgent (sic) design model must not only explain why these finches have been recently re-designed to use man-made materials to 'medicate' their nests by why it did this having designed the nest parasites to infest nests and suck the blood of chicks in the first place. How is it intelligent to have to design a solution to a problem you deliberately caused in the first place and then why design a solution that causes genetic damage to the chicks it was designed to protect?
Believe it or not, there are people who believe this is a sensible, even logical, explanation of how this sort of thing evolves!
Any cDesignproponentsists (sic) prepared to have a go at an explanation without giving away the fact that ID is fundamentalist Bible literalism in disguise?
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