Abstract: The Suaedas salsa saltmarsh is a typical estuarine wetland along the coast of Yellow Sea and provides an important stopover habitat for migratory waterbirds. However, within a saltmarsh-mudflat estuarine wetland landscape mosaics, how can the waterbirds, especially the shorebirds, use this kind of wetland and the ecological contribution of this habitat on the diversity of shorebirds has rarely been documented. Here, we systematically conducted a waterbird count and behavioral observation of the shorebirds in two adjacent S. salsa saltmarsh and mudflat tideland habitats at Liaohekou National Nature Reserve from 2017 to 2019 to examine the community composition and habitat use differences between these two habitat types. In total, 6,348 waterbirds belonging to 4 families and 28 species (saltmarsh: 13 species; mudflat: 27 species) were recorded within two 400m*500m sampling plots, and the avearge species richness was higher in mudflat than that in S. salsa saltmarsh during both migratory seasons (spring: t=-2.342, df=19, P=0.03; fall: t=-3.656, df=30, P=0.001). Furthermore, we found there were significant difference in the shorebird community composition between two habitats: the S. salsa saltmarsh were dominantly used by large-bodied shorebirds (Numenius madagascariensis, N. arquata and Pluvialis squatarola) while the adjacent mudflat was largely used by small birds (Charadrius alexandrinus and Calidris alpina). This indicates that the S. salsa saltmarsh has a distinct ecological function on the community construction and maintenance of species diversity of local waterbirds. In addition, behavioral data showed the foraging (58.71-93.26%) was dominant behavior of shorebirds in two habitats, but significant higher percentage of roosting behavior (23.3%) was found in the S. salsa saltmarsh, particularly during the spring stopover stage. This indicated that the saltmarsh was also an important roosting habitat, except for the foraging site, for many shorebirds that could not be replaced by adjacent intertidal mudflat. While the general biodiversity indices (species richness and abundance) of saltmarsh were lower than that of mudflat, the large proportion of shared species (12 species) in two habitats implied that these two kind of habitats were different and yet complementary stopover site for shorebirds across the saltmarsh and mudflat tidal wetland mosaics.

Key words: S. salsa saltmarsh, Community structure, Habitat use, shorebirds, Liaohe Estuary wetland