The introduced red swamp crayfish (Procambarus clarkii) Girard, 1852, as prey for birds in Italy: a first citizen science-based checklist

Abstract: Invasive alien species (IAS) are negatively impacting native species and ecosystems worldwide. Among them, the red swamp crayfish (Procambarus clarkii) has been extensively studied in Italy due to its detrimental effects on ecosystems and native crayfish species. While extensive data are reported on the diet of P. clarkii, less is known about its role in the trophic web as prey for birds. In this study, we gathered online data from scientific databases and citizen science sources for the first time, obtaining information on the bird species preying on P. clarkii in Italy. Due to the heterogeneity of collected data, two bird lists were compiled based on record types. When species identification was assessed by the authors, a reliability score was assigned for each crayfish species identification. Using strictly filtered data, we recorded 26 bird species from eight Italian regions. When including all available records, both filtered and unfiltered, two additional regions were identified, bringing the total to 46 bird species. Most of these species are considered strictly carnivorous, but surprisingly, three species (Anas platyrhynchos, Fulica atra, and Gallinula chloropus) are primarily herbivorous. These results indicate (i) the paradoxical role of P. clarkii as a prey for a wide range of bird species, including both carnivores and herbivores, and species not exclusively tied to wet ecosystems, (ii) a spatial pattern of predation at a national scale and (iii) the role of citizen science data as a valuable tool for studying the ecology and role of invasive crayfish species in trophic webs.