Paper, plastic, and… cigarette butts?
This is Sandra Tsing Loh with the Loh Down on Science.
Urban birds scrounge up people’s trash to build their nests. No butts about it! Just like cigarettes aren’t good for you or me, they aren’t good for baby birds! But mama birds prefer them over other trash—why is that?
Enter Constantino Macía Garcia at the Universidad Nacional Autónoma de México. To answer this question, he manipulated the nests of finches. First, he removed any cigarettes from the nest. Then he added ticks! Yep, those nasty blood-sucking parasites. He watched while the mother finches rebuilt their nests.
So, when did Garcia observe cigarette butts in the reconstructed nests? When Mama Finch had originally used butts and when Garcia had added ticks. The more Mama Finch used to begin with, the more she added to rebuild!
Nicotine, the drug in cigarettes, is toxic to us as well as other critters. So, Garcia thinks, perhaps finches use them to guard their nests against parasites.
Cigarette butts… the pesticide of choice for finches! I suppose no harm, no fowl! (Sorry!)