Everyone is talking about ticks this year, for good reason: this year’s tick forecast is especially bad. But humans aren’t the only ones worried about the horrible little buggers. It seems like at least one bird species safeguards its nests against ticks with a surprising piece of litter. Cigarette butts.
Scientists have long known that birds in contact with humans sometimes use trash to build their nests. A team of Mexican scientists noticed a peculiar behaviour in house finches: They were lining their nests with toxic cigarette butts. Past research has shown the butts seem to keep ticks out of nests. But were the birds aware of that, or were they just picking whatever trash they could find?
“What our experimental manipulations show...is that cigarette butts are added in response to an increase in the number of ectoparasites [like ticks] in the nest,” the researchers write in the study published last week in the Journal of Avian Biology “and thus must be regarded as a form of self-medication.”
The researchers observed the finches on the campus of the Universidad Nacional Autónoma de México, and put an artificial lining into their nests. They then put live ticks on ten of the nests, dead ticks on another ten, and had 12 control nests where the artificial lining had no ticks on it. Then the researchers just needed to wait and see how many much cigarette butt fibre the birds found and added to the nest.
When they re-observed the nests after the chicks had matured and flown away, their results were clear: Only the finches in the live tick-filled nests were lining their nests with a significant amount of cigarette butt material.
There are definitely some caveats. This is a fairly unnatural experiment, the researchers were using artificial nests, and they don’t know if finches living in non-urban environments exhibit similar behaviours. Also, they don’t know for sure if the birds know what they’re doing, or maybe they just “learn to associate butt odour to the relief from ectoparasites cues.”
The study doesn't mention what effects the cigarette butts have on ticks, just that more cigarette butts means fewer ticks. And it does seem that the benefits of the finches using poisonous cigarette butts against ticks outweigh the harm.
Others thought the study was exciting. Researcher Steve Portugal from the University of London told New Scientist this was an example of “animals being innovative and making use of the materials available to them.”
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