Diet and plastic ingestion of a remote, inland colony of glaucous gulls (Larus hyperboreus) in Arctic Canada

Glaucous gulls (Larus hyperboreus) are diet generalists that usually nest in coastal colonies with other species of seabirds, often preying upon their neighbours’ eggs and young. Near a landfill on Cornwallis Island, Nunavut, a colony of glaucous gulls inhabits a small island within Tern Lake where they are the only seabird species nesting. Given that most information of glaucous gull diet comes from birds nesting among other seabirds, this study aimed to determine whether their diet differs from other more typical nearby populations. In addition, we assessed whether these gulls were likely foraging at the nearby landfill. We collected 107 regurgitated glaucous gull pellets from this colony in 2024 and 2025, dissected them, and identified prey items to the lowest possible taxonomic level, as well as any ingested anthropogenic debris. Gulls were feeding predominantly on northern collared lemmings (Dicrostonyx groenlandicus) in both years (frequency of occurrence, FO, of 97%), which contrasts with most previous accounts of glaucous gulls feeding at higher trophic levels on marine prey and young of other seabird species. Other prey items found in this inland colony included mollusk shells, fish vertebrae, bird eggshells, and low amounts of anthropogenic debris including plastic (FO 9%). Our study provides strong evidence of dietary plasticity in glaucous gulls in this inland habitat.