Overwintering in the East China Sea or Japan Is Linked to Concerningly Low Survival in a Migratory Shorebird

ABSTRACT Aim Site network approaches to waterbird conservation are easily biased towards species that occur in high densities and locations and periods of the annual cycle with dense concentrations of birds, thereby potentially failing to address underlying factors driving certain population declines. Here, for shorebird populations that migrate along the East Asian–Australasian Flyway, we examine the extent to which recent conservation efforts at key sites in the Yellow Sea—that is, sites that are vital for stabilising densely concentrated , rapidly declining shorebird species—might address factors underlying low adult survival and steep population declines in shorebird species that migrate and winter along a broad front (i.e., the East China Sea, Yellow Sea and Japan). Location East Asia. Methods and Results Using geolocator‐derived migration tracks, an integrated survival model and a population matrix model to estimate winter‐population‐specific survival rates and population trends in a quintessential East Asian shorebird population—the arcticola subspecies of the Dunlin ( Calidris alpina )—we show that in 2010–2014 differences between arcticola winter populations in the intensity of their declines were most likely linked to conditions on their wintering grounds, with individuals that wintered in the East China Sea or Japan showing the steepest population declines (mean: −12% year −1 [50% credible interval: −3%, −22%] and −17% year −1 [−6%, −30%], respectively) and individuals that wintered in the Yellow Sea surprisingly stable (+4% year −1 [−5%, +14%]). Main Conclusions For shorebird populations that winter in East Asia and migrate along a broad front, additional conservation efforts in the East China Sea and Japan are likely necessary to reverse population declines.