PS 52-191 - Assessing plastic ingestion in birds of prey from British Columbia, Canada

Background/Question/Methods

Since first being introduced for broad-scale public use in the 1960s, plastic has become one of the most pervasive and ubiquitous forms of pollution globally. The potential fate and effects of plastic pollution on birds is a rapidly growing area of research, but data on terrestrial and freshwater species has been extremely limited in the literature. Birds of prey have been particularly understudied, with no published data on plastic ingestion in raptors in Canada to date, and very few studies globally. A baseline understanding of plastic ingestion in these species will contribute important information about susceptibility and vulnerability across species ranges, which is necessary to inform future investigations of population level risks and conservation priorities. To assess the ingestion of plastic in birds of prey, we analyzed the contents of the upper gastrointestinal tracts from specimens that were collected for post-mortem examination as part of broader wildlife disease surveillance strategy in British Columbia, Canada. A total of 234 individuals across 15 species were collected between 2013 and 2021. Upper gastrointestinal tracts were assessed for plastics and anthropogenic particles >2 mm in size.

Results/Conclusions

Of the 234 specimens examined, only five individuals across two species had evidence of retained anthropogenic particles in the upper gastrointestinal tract. Two of 33 bald eagles (Haliaeetus leucocephalus, 6.1%) had retained plastics in the gizzard, while three of 108 barred owls (Strix varia, 2.8%) had retained plastic and non-plastic anthropogenic litter. The remaining 13 species were negative for retained anthropogenic particles >2mm in size (N = 1-25). These results demonstrate that raptor species do not appear to ingest and retain larger anthropogenic particles, though foraging guild and habitat may influence species vulnerability. Low sample size also limits interpretation in some species. Future research should focus on microplastic accumulation in the upper and lower gastrointestinal tracts, as these particles may represent a more likely route for chronic exposure and secondary health impacts in these high trophic-level species.