Abstract: The Liaohe River estuary wetland, a crucial waterbird habitat along the East Asia-Australasia Flyway, has mainly been studied for regional waterbird distribution and changes in habitat area and quality. However, studies on the identification, seasonal distribution, and long-term population trends of keystone species are scarce. Using waterbird monitoring data between 2010 and 2023, criterion in wetlands of international importance, and the TRIM model (Trends and Indices for Monitoring data), we identified keystone species and their important sites of seasonal distribution, and analyzed long-term population trends. A total of 133 species from 9 orders and 18 families were recorded, with Charadriiformes being the most numerous. Fifty-four keystone species met the criterion in wetlands of international importance, distributed across 188 important sites. There were significant seasonal differences in the habitat distribution and occurrence frequency of different waterbird species. Important stopover sites were identified, including Nanxiao River, Delta Reservoir, Jiuhuzui, Erjiegou Bridge, Sandao River, and Tanhai Station. Some sites were also served as breeding grounds for gull species and wintering grounds for cranes and geese. From 2010 to 2023, the number of habitats meeting the criterion in wetlands of international importance significantly increased. Total population size of all the species showed an increasing trend, but the population of species like Greater White-fronted Goose (Anser albifrons), Siberian Crane (Leucogeranus leucogeranus), Red-crowned Crane (Grus japonensis), and Grey Plover (Pluvialis squatarola) exhibited declines. Our results indicated that increasing waterbird numbers could lead to insufficient resource carrying capacity in the Liaohe River estuary wetland if the protected areas were not expanded.

Key words: Liaohe River estuary wetland, key species, population trend, TRIM model