Upper tidal flats are disproportionately important for the conservation of migratory shorebirds.

Migratory animals play vital ecological roles in ecosystems worldwide, yet many species are threatened by human activities. Understanding the detailed patterns of habitat use throughout the migration cycle is critical to developing effective conservation strategies for these species. Migratory shorebirds undertake some of the longest known migrations, but they are also declining precipitously worldwide. To better understand the dynamics of shorebird declines along the East Asian-Australasian Flyway, we quantified the spatiotemporal foraging distribution of 17 migratory shorebirds at two critical stopover sites. We found that shorebirds exhibit substantial interspecific and site-specific differences in their foraging distributions. Notwithstanding these differences, however, the upper tidal flats appear to be especially important to most shorebirds by providing more than 70% of the birds' cumulative foraging time, twofold greater than their proportional area. Because the upper tidal flats are also more prone to coastal development, our findings may help to explain why shorebird populations along the flyway have declined much faster than the overall rate of tidal flat loss. Our work highlights the importance of protecting upper tidal flats to conserve migratory shorebirds and demonstrates the value of a detailed ecological understanding of habitat usage by migratory animals for conservation planning.