Short-term flooding in non-rice croplands provides stopover habitats for migrating waterbirds

Substantial areas of inland wetlands have been transformed into croplands globally. Although seasonal flooding in rice fields is well known to provide alternative habitats for species dependent on wetlands and aquatic environments, it remains unclear whether temporal flooding in other non-rice croplands, such as wheat fields, can serve a similar function. By focusing on the latest farming policy of short-term flooding on non-rice croplands in Japan, we investigated the diversity of a whole avian community and the major functional groups including waterbirds and globally declining migratory shorebirds in flooded croplands and conventional dry croplands from flooding to after-dried-out periods. We showed that species richness and abundance of waterbirds and shorebirds were significantly higher in the flooded croplands than in conventional dry croplands and dried-out croplands after flooding. The density of shorebirds in flooded non-rice fields was equivalent to that in the flooded rice fields in other regions. In contrast, terrestrial bird abundance and species richness were not significantly different between the land use types in both periods. Moreover, shorebird abundance and species richness decreased with the progressing season, which indicates their stopover habitat utilization might be highest at the peak of the migration. These results emphasize that short-term flooding even in non-rice fields is effective for serving artificial habitats to migrating waterbirds, potentially contributing to expanding waterbird conservation to broader regions and periods in which rice has not been growing.