Alternative habitat: the importance of the Nanpu Saltpans for migratory waterbirds in the Chinese Yellow Sea

Many shorebird populations are in decline along the East Asian-Australasian Flyway. The rapidloss of coastal wetlands in the Yellow Sea, which provide critical stop-over sites during migration,is believed to be the cause of the alarming trends. The Yalu Jiang coastal wetland, a protectedarea in the north Yellow Sea, supports the largest known migratory staging populationsof Bar-tailed Godwits Limosa lapponica (menzbieri and baueri subspecies) and Great KnotsCalidris tenuirostris. Monitoring of the macrozoobenthos food for these shorebirds from 2011to 2016 showed declines of over 99% in the densities of the bivalve Potamocorbula laevis, themajor food here for both Bar-tailed Godwits and Great Knots. The loss of the bivalve might becaused by any combination of, but not limited to: (1) change in hydrological conditions andsediment composition due to nearby port construction, (2) run-off of agrochemicals from theextensive shoreline sea cucumber farms, and (3) parasitic infection. Surprisingly, the numbersof birds using the Yalu Jiang coastal wetland remained stable during the study period, exceptfor the subspecies of Bar-tailed Godwit L. l. menzbieri, which exhibited a 91% decline in peaknumbers. The lack of an overall decline in the number of bird days in Great Knots and in thepeak numbers of L. l. baueri, also given the published simultaneous decreases in their annualsurvival, implies a lack of alternative habitats that birds could relocate to. This study highlightsthat food declines at staging sites could be an overlooked but important factor causing populationdeclines of shorebirds along the Flyway. Maintaining the quality of protected staging sitesis as important in shorebird conservation as is the safeguarding of staging sites from land claim.Meanwhile, it calls for immediate action to restore the food base for these beleaguered migrantshorebirds at Yalu Jiang coastal wetland