A recent study has confirmed that many bird species across the globe actively gather cigarette butts to line their nests. This behavior has been observed in urban songbirds, some of which even nest in ashtrays. The primary reason behind this unusual nesting material has been linked to its efficacy in deterring parasites, as confirmed by researchers at the University of Łódź in Poland.

The researchers focused on blue tits, a species that readily accepts both natural cavities and human-made nest boxes. These birds often share their nests with various pests, such as blowflies and bloodsucking parasites like ticks and fleas, which can be particularly disruptive to adult birds and helpless chicks. By closely monitoring 99 blue tits in both urban environments and nearby forests, the study aimed to understand the nesting preferences of these birds in relation to their public hygiene.

For their experimental setup, the researchers provided three types of nest boxes: conventional ones that birds could decorate themselves, sterilized boxes with synthetic moss and cotton, and boxes that contained two cigarette butts. The findings revealed that nests with the cigarette butts had fewer parasites, lending robust support to the theory that these birds instinctively utilize this unusual material to enhance their nest health and protect their young from potential infestations.