Minimal Accumulation of Microplastics in Shorebirds at Migratory Stopover Sites in Canada

We quantified egested microplastics and identified plastic polymer composition for three shorebird species (Western Sandpiper Calidris mauri, Dunlin Calidris alpina, and Semipalmated Sandpiper Calidris pusilla) by collecting fecal samples at major stopover sites on the Pacific and Atlantic coasts of Canada in 2022. The sampling effort resulted in a total of 133 individual fecal samples, 93 from the Pacific sites and 40 from the Atlantic sites. Frequency of occurrence (FO) of microplastics was generally low and ranged by species: Western Sandpiper (FO = 13%, n = 11/87), Dunlin (FO = 17%, n = 1/6), and Semipalmated Sandpiper (FO = 3%, n = 1/40). We isolated a total of 14 plastic microfibers from 13 birds, of which polyester was the most common polymer (n = 6), followed by polypropylene (n = 4), and polyamide (n = 4). The colour of microplastics were white (n = 9, 64%) and black (n = 5, 36%), and the average length was 2.35 mm (SD = 1.18 mm). This study adds Western Sandpiper and Semipalmated Sandpiper to the list of shorebirds that are demonstrated to ingest microplastic pollution and underscores the need to understand the consequences of such ingestion.