Spatiotemporal differences in plastic biovectoring among three sympatric waterbirds

Abiotic vectors of plastic and their impact in natural areas have been extensively studied, whereas biotic vectors have received less attention. Recent studies demonstrate that birds can act as powerful agents of plastic transport, moving large quantities of plastic from landfills to natural habitats through a process called biovectoring, causing pollution hotspots. While most studies have focused on single species, the present research broadens this approach. Here we compared the quantity, composition and spatio-temporal variation of plastic biovectoring among three co-existing waterbird species foraging on landfills near a coastal wetland: white storks, yellow-legged gulls, and lesser black-backed gulls in Cádiz Bay Important Bird Area (CBIBA; 152 km2), Spain. We analysed 177 regurgitated pellets (42-74 per species), weighed their plastic content and used FTIR-technology to identify and classify polymer composition. We then characterized each plastic item by shape, size and colour, enabling interspecific comparisons using multiple correspondence analysis. Finally, we combined census, GPS data and the plastic obtained from the pellets to develop a daily plastic loading model for each species. We found that white storks transported the most plastic per pellet (0.14 g by median), compared to 0.034 g for yellow-legged and 0.026 g for lesser black-backed gulls. In general, gulls carried similar types of plastic items, with more film and larger sizes than storks. In total, 531 kg of plastics were estimated to be biovectored into the CBIBA from landfills in 2022, with deposition being higher in winter and lesser black-backed gulls transporting about 54 % of the total, followed by yellow-legged gulls with 30 % and white storks with 16 %. In addition, we also identified major seasonal and spatial differences among species. Our results highlight the importance of using a multi species approach to plastic biovectoring, which is essential to understand and estimate its environmental impact, and to inform management strategies.

JCP received an FPU (Formación de Profesorado Universitario) grant (financed by MIU, Spanish Government). LL was partly funded by Methusalem Project 01M00221 (Ghent University). This work was supported by the Junta de Andalucía «proyecto de I + D + i PY20_00756: GuanoPlastic» (IP: AJG) and the University of Cadiz research results transfer office project OT2022/047: “Disuasión de gaviotas y otras aves en vertederos: efecto sobre los parques eólicos adyacentes” financed by Verinsur S.A (IP: FH). YLG project was funded by: Proyecto integrador CSIC-SUMHALL-LifeWatch FEDER AndalucíaWP7: Combining field data, citizen science and IoT to monitor anthropogenic impacts on the Andalusian biodiversity and society CoIP WP7. LWE2103009. UvA-BiTS studies are facilitated by infrastructures for e-Ecology, developed with the support of NLeSC and LifeWatch and carried out on the Dutch national e-infrastructure subsidized by the NWO Domain Science (2021.030) with support of the SURF Cooperative. GPS tracking of LBBG from Schiermonnikoog and Ijmuiden is part of the Open Technology Programme, project Interactions between birds and offshore wind farms: drivers, consequences and tools for mitigation’ (project number 17083), which is financed by the Dutch Research Council (NWO) Domain Applied and Engineering Sciences, in collaboration with public and private partners (Rijkswaterstaatand Gemini wind park). The Belgian tracking devices and associated infrastructure were funded by LifeWatch Belgium and by the Research Foundation–Flanders (FWO) grant G0E1614N to WM and LL.

Peer reviewed