Birds have been using tobacco filters for quite some time and there are several studies on this. This new habit can cause problems in birds.
We already know that tobacco consumption causes death. The nicotine it contains is highly addictive, and around 70 of its chemical compounds are associated with cancer. Although these data correspond to the inhalation of tobacco, 30 substances continue to be carcinogenic in other forms of consumption such as chewing or vaporization.
These chemical compounds are toxic to smokers and many other species sensitive to these substances.
Antimicrobial activity has been detected in tobacco extracts, which inhibit the growth of pathogenic bacteria and fungi. This is why macerated tobacco is used as an insecticide and acaricide in crops.
All this data is essential for birds.
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nests with nicotine
The Renaissance botanist and chemist Paracelsus is credited with concluding that “everything is poison and nothing is poison, only the dose makes the poison“. We now know that the minimum dose at which a substance becomes toxic depends on the species receiving it and the weight of the individual. So the same amount of nicotine in a puff of smoke inhaled by a 7 kilo baby does not affect the same amount as a 70 kilo adult. In the baby it will have a much higher toxicity.
And the same thing happens in animals. An insect of a few milligrams, or a mite of the order of a microgram, has a much lower toxic dose than a sparrow of 30 or 40 grams.
This is the main benefit that birds derive from tobacco butts. Once the cigarette is consumed, the cellulose that makes up the filter is impregnated with nicotine. Some birds crumble the filter and intertwine its component strands with the twig weaving of their nest. We don’t know why they do this — cellulose is an excellent thermal insulator, and they might do so by researching this feature — but we do know its effects.
It is a fact that the presence of cigarette filter remains greatly reduces the number of parasites in the nest, especially insects and mites. This is probably due to the insecticidal effect of nicotine. In arthropods, this alkaloid affects brain development and acts as a neurotransmitter disruptor, reducing the ability to control muscles and the heart, which often has a fatal outcome.
Not everything is good for the nest
This apparent advantage is not necessarily the case. On the one hand, the use of butts by birds as raw material for their nests can have negative consequences on their health and especially that of their chicks. They maintain prolonged contact with everything in the nest and, through the skin, they can absorb these products. In addition, they frequently deposit food in the nest which they will consume later. If leftover cigarette filters, nicotine and other dangerous compounds can leach into food and enter the food chain. Only the dose makes the poison said Paracelsus. But birds don’t usually read Paracelsus.
The apparent benefit that the absence of parasites may bring does not outweigh the inherent risks of sleeping in a poisoned bed.
But there is another problem underlying this behavior. And it is that if many birds have the possibility of decorating their nests with filter scraps, it is because they have them within their reach.
The cigarette butt as a contaminant
Not surprisingly, these behaviors were observed primarily in urban populations. Cigarette butts are one of the most common litter in the world. It is estimated that approximately 5.5 billion cigarettes are produced worldwide each year and discarded butts reached some 1.2 million tonnes in 2020, a value that could increase by up to 50% in 2025.
Since they are frequently thrown on the ground, it is normal that they end up being carried away by the wind or by water, and end up in natural environments.
Filters are usually made from non-biodegradable materials, which take years to break down naturally. Additionally, the contaminants that remain in the cigarette butt after smoking cigarettes have antimicrobial capacity, inhibiting the growth of many spoilage organisms. They are toxic to plants, algae, fish, amphibians… Of course, their toxicity increases the more recent the cigarette butt, however evidence of toxicity has been found in microalgae up to five years after the cigarette butt was discarded.
REFERENCES:
Bonanomi, G. et al. 2020. The Fate of Cigarette Butts in Different Environments: Decomposition Rates, Chemical Changes, and Ecotoxicity Revealed by a 5-Year Decomposition Experiment. Environmental pollution, 261114108. DOI: 10.1016/j.envpol.2020.114108
Lans, C. et al. 2011. Biological parasite control for poultry and rabbits in British Columbia, Canada. Journal of ethnobiology and ethnomedicine, 7(1), 21. DOI: 10.1186/1746-4269-7-21
Morris, M. et al. 2018. Developmental nicotine exposure affects larval brain size and the adult dopaminergic system of Drosophila melanogaster. BMC
Developmental biology, 18(1), 13. DOI: 10.1186/s12861-018-0172-6
Slaughter, E. et al. 2011. Toxicity of cigarette butts and their chemical constituents to marine and freshwater fish. tobacco control, twenty(Suppl 1), i25-i29. DOI: 10.1136/tc.2010.040170
Suárez-Rodríguez, M. et al. 2013. Incorporation of cigarette butts into nests reduces ectoparasite nest load in urban birds: new ingredients for an old recipe?
Biology Letters, 9(1), 20120931. DOI: 10.1098/rsbl.2012.0931
Torkashvand, J. et al. 2020. Discarded Cigarette Butt as a Well-Known Hazardous Waste: A Comprehensive Systematic Review. Hazardous Materials Journal, 383121242. DOI: 10.1016/j.jhazmat.2019.121242
Vorvick, LJ et al. 2020. tobacco risks. Medline Plus.
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