Silver gull carcasses host unique carrion insect communities on a nearshore island

Abstract

Island ecosystems offer unique opportunities to study the dynamics of species that rely on ephemeral resources such as carrion. This study investigated the necrophagous insect communities associated with carrion of silver gulls (Chroicocephalus novaehollandiae) on a small nearshore island off the east coast of Australia, to assess how necrophagous insect communities on islands compare with the mainland community, and the degree to which these communities varied over time. Over three breeding seasons, we analysed what insect species were colonising gull carcasses and, using baited traps, compared total adult community composition and richness of carrion-associated insect species on the island with the adjacent mainland. Our findings reveal that an island separated by less than 500 m from the mainland can harbour distinct carrion-breeding fly assemblages. These assemblages vary between years but are notably dominated by a potential seabird-carrion specialist fly—the littoral species Calliphora maritima. These results underscore the importance of seabird carrion as a critical resource for necrophagous insects on islands and contribute to our understanding of how island environments influence insect community dynamics and specialisation.