Impacts of habitat loss on migratory shorebird populations and communities at stopover sites in the Yellow Sea

Migratory birds generally use one or more stopover sites for rest and/or refuelling during long-distance migration where a large abundance of diverse species can concentrate into temporary assemblages. Habitat loss at stopover sites has resulted in population declines for many species, in particular shorebirds along the East Asian-Australasian Flyway. However, the consequences of habitat loss on the characteristics of bird assemblages at specific stopover sites are still unclear. We compared the results of shorebird surveys during northward migration between an “early” study period (1996 to 2005) and a “late” study period (2013 to 2014) at 14 stopover sites on the Yellow Sea coast in China, where a large tidal habitat area for shorebirds was destroyed. The total tidal flat area decreased by 35.6%, while the total shorebird abundance decreased by 7.8%, suggesting increased competition for space and food among shorebirds at stopover sites. However, changes in bird abundance (−72.9% to +210.0%) were not significantly related to tidal flat area changes (−71.2% to −2.0%) at the sites. Bray–Curtis similarity analysis indicated that community composition significantly differed among sites, but was similar within sites between study periods. This suggests habitat conditions, which determine the composition of bird communities, exhibited consistent site differences between study periods. These results imply that habitat loss at one stopover site is unlikely to be offset by conserving others; thus, protecting an extensive number of existing key stopover sites is crucial for the conservation of migratory birds.