Documentation of microplastics in the gastrointestinal tracts of terrestrial raptors in central California, USA

Microplastics are persistent environmental contaminants that to date have been studied primarily in aquatic systems, but few studies have examined their prevalence or impact in terrestrial trophic networks. A recent study documented microplastics in the gastrointestinal (GI) tracts of terrestrial raptors in central Florida. We used protocols based on that study to develop a baseline dataset of microplastics in the GI tracts of terrestrial raptors on the central coast of California. In 2021, Pacific Wildlife Care, a wildlife rehabilitation center in Morro Bay, CA, provided 16 raptor carcasses: three red-tailed hawks (Buteo jamaicensis), four red-shouldered hawks (Buteo lineatus), two great horned owls (Bubo virginianus), and seven barn owls (Tyto alba). We found microplastics in the GI tracts of all 16 birds, with a mean (± SE) of 12.25 (± 1.89) microplastic particles per bird. Of the 196 microplastic particles we observed, microfibers were the most abundant (58%), followed by microbeads (34%), and microfragments (8%). However, microbeads were the most prevalent, found in all 16 birds, followed by microfibers (15 birds), and microfragments (6 birds). The chemical composition and source of these contaminants remains unclear, along with the physiological and ecological implications to raptor populations and their ecosystems, and the extent to which microplastics occur in other terrestrial species and regions in California.