Everyone knows the scene: A nice lawn, a clean sidewalk, a park picnic -- marred by cigarette butts. Oddly enough, sparrows and finches in Mexico City are lining their nests with the guts of used cigarette filters.

Don’t get me wrong, I’m glad someone is cleaning up, but who uses a stranger’s cigarette butt for housing? These birds have a problem, and it’s a problem that needs to be fixed now rather than later. Think of the burden that a city full of sick birds would place on the healthcare system.

However, quitting cold turkey may not be so easy. Researchers believe that these birds use the cigarette's filter to provide cushy insulation for their nest, meanwhile the nicotine works as a pesticide. Nicotine derivatives were used as organic pesticides until 2008, when a request was filed and subsequently granted by the EPA to effectively ban them because nicotine was considered too toxic.

But, the bottom line for the sparrows and finches is that building with butts works. A study published in Biology Letters found significantly fewer parasites in nests built with used cigarette filters than in nests built with clean filters, suggesting it’s the chemicals released into the filter through smoking that repel parasites, not the filter itself.

So the question is, are the birds deliberately using nicotine to ward off pests, or is just lucky for them that the warm and plentiful fluffy white stuff keeps out the bugs? Certain birds have been known to line their nests with scented vegetation to keep bugs away -- female blue tits, for example, use lavender, curry, and mint in their nest to repel insects.

 

Non-human animals using substances to treat symptoms or diseases is called zoopharmacognosy, and it's more common than you'd think. For example, white-faced capuchin monkeys rub their fur with millipedes and leaves from the piper plant to keep lice, ticks, and mosquitoes away, while red colobus monkeys eat charcoal to relieve indigestion.

But self-medication is a slippery slope, especially if you start with cigarettes -- first it’s nicotine for mites, next it’s a little whiskey for depression, and then it’s a pinch, just a pinch, of cocaine for a toothache (and sparrows don’t even have teeth!). Now you’re hooked and it’s a downward spiral. Soon, the bank takes your nest, the state takes your eggs, and you’re left back where you started -- picking out discarded cigarette butts from the gutter. Now imagine that on a massive scale. Avian crime will skyrocket, and cuckoos will seem model citizens by comparison.

These sparrows and finches need help quitting before it’s too late. We’ll have to make some sort of nicotine gum that works with beaks. Maybe a chewy worm or something.