Abundance of plastics in an agricultural environment and their selection for nest building by the great tit (Parus major)

Continental plastic production is on the rise, making these materials significant pollutants with a growing recognition of their impact on agricultural environments. The aim of this study was to provide information about the abundance of plastics in an agricultural environment around the town of Sagunto (Valencia, eastern Spain) and on the use of plastics by the great tit (Parus major), a breeding species in these agricultural areas. Environmental plastic samples were collected using the quadrat method, applied randomly across the study area. Sixty-four samples were collected. Data on the great tit were collected from 35 successful nests, which were gathered after the chicks had fledged. Our results show that 65.6% of the environmental samples contain plastics. From the abundance per square meter, we estimated a density of 18,750 plastic pieces per hectare at the studied agricultural ecosystem. Among the 19 nests containing plastics (54.3%), 556 plastic pieces were found, with the number of pieces per nest ranging from 1 to 153 (mean = 12 ± 1.28; N = 35). Furthermore, the presence of a nearby landfill in Sagunto showed no correlation with the abundance of plastics in either the environment or the nests. This suggests that plastic abundance depends on very local sources, which in this case might be the consequence of farmers and laborers not removing the plastics after use. The great tit selects filament plastics and the colors black and red to incorporate into their nests.