How waterbird communities respond to seasonal and environmental factors in rice fields adjacent to a Ramsar wetland

Natural wetlands have been lost or degraded worldwide, negatively impacting waterbird populations. However, many species have capitalised on the creation of complementary habitats such as rice fields, a common and widespread type of artificial wetland. Despite the significance of rice fields as supplementary habitats for waterbirds, few studies have explored how waterbirds use these wetlands across seasons and how they respond to different local environmental factors. We surveyed waterbird communities in rice fields near Anhui Shengjin Lake National Nature Reserve, a Ramsar site, during the rice growing periods and the post-harvest periods from 2023 to 2024, to analyse the impact of environmental factors on the metrics of community diversity. We observed 15,085 waterbirds of 33 species in the rice fields, with diversity indices that were generally higher in rice fields inside the reserve than those outside the reserve in most periods. Waterbird densities peaked during the seedling and pre-wintering periods. Species richness, the Shannon-Wiener diversity index, and the densities of ducks and shorebirds were highest during the seedling period, while gull densities peaked in the flowering period. In contrast, goose densities were highest during the pre-wintering period. Rice fields with larger areas, irregular shapes, deeper water, higher drain density, and closer proximity to larger adjacent rice fields and Shengjin Lake supported higher waterbird densities and species richness. Human disturbances from main roads and settlements negatively affected waterbirds. However, during certain periods, waterbirds were attracted by human activities that may expose food resources in rice fields. These findings provide important implications for waterbird conservation in these artificial wetlands, which are of global significance given their important role in the context of worldwide wetland loss and degradations.