Assessing plastic ingestion in the White stork (Ciconia ciconia) through regurgitated pellets.

Pollution is one of the main factors that threaten biodiversity nowadays. Plastic waste is a global problem which impacts not only on the marine environment but also on the terrestrial one. Great amounts of this kind of refuse are compiled in landfills, where lots of avian species feed. In contrast to seabirds research, there are limited studies that have considered how plastic is being ingested by land birds even when they are being affected both physically and at an endocrine level. We tried to assess the number of plastics and microplastics ingested by individuals of a White stork (Ciconia ciconia) colony in central Spain by collecting regurgitated pellets. The chemical composition of the elements was determined, as well as the relation between the amount of ingested plastic by individuals and their use of a landfill. Our results show that 3.44% of the pellet was formed by plastic (n = 50). Polyethylene, polystyrene, polypropylene and PET were the most abundant polymers, all of them being potentially problematic to the organism according to the literature. Each polymer was identified by Fourier transform infrared attenuated total reflectance spectroscopy (FTIR-ATR). We observed that the total amount of ingested plastics was stable along the use of the landfill, meaning White storks obtained plastic not only from anthropogenic sources but also from natural areas, indicating its high rate of pollution. Our study remarks the importance of addressing plastic ingestion in White storks as well as other terrestrial species, not only to understand the possible damage to the population but also to the whole ecosystem.