Tree sparrow nests as indicators of plastic pollution in anthropized environments

Abstract

Nowadays, plastic stands out as one of the most widespread pollutants in natural environments. While much research has concentrated on plastic pollution in marine ecosystems, it's essential to acknowledge that plastic also impacts terrestrial ecology. Birds, which construct nests using a variety of locally available materials, are not exempt from this influence, as they sometimes incorporate plastics of human origin into their nesting materials. This study seeks to investigate whether the propensity to include such anthropogenic materials also extends to birds that construct nests within enclosed spaces, such as nest boxes. To accomplish this, we examined a total of 11 tree sparrow nests, categorizing the materials comprising these nests and placing a specific focus on the portion derived from human activities, notably plastics. Additionally, we explored whether there was a preference among these birds for specific colours and types of anthropogenic materials when constructing their nests, which might be influenced by the availability of these materials in the local area. Our findings revealed that vegetal materials constituted the primary component of the nests, followed by animal-derived materials and anthropogenic materials. Interestingly, this final category of material is present in all of the examined nests and there appeared to be a distinct preference among the birds for incorporating black and filamentous anthropogenic materials over other types and colours. This suggests that these birds may exhibit selectivity in their choice of human-made materials, possibly due to factors related to availability, suitability for its resistance or simply due to confusing it with similar naturally occurring material.