A case study from a critical stopover site in the East Asian-Australasian Flyway provides lessons for optimal high-tide roost management to support shorebird conservation

Abstract

Land reclamation has significantly reduced tidal flats globally, leading to a sharp decline in shorebird populations and highlighting the urgent need for habitat restoration. Following reclamation, tidal flats are predominantly submerged during high tides, forcing shorebirds to seek roosts. To evaluate the effectiveness of various restoration and management methods on high-tide roosts, we studied shorebird utilization in Southern Jiangsu, China, a crucial staging site along the East Asian-Australasian Flyway. We conducted bird surveys during the autumn migration at six high-tide roosts: aquaculture pond using environmentally-friendly farming (EFF) (Site 1), restored and reserved roost (Site 2), unused reclaimed land (Site 3), unrestored flat (Site 4), restored flat (Site 5), and reclaimed farmland (Site 6). We used Bayesian generalized additive mixed effect models (GAMM) to analyze the effects of tide height and proportion of bare ground on shorebird density at the roost sites, and Permutational Multivariate Analysis of Variance (PERMANOVA) and nonmetric multidimensional scaling (NMDS) to compare community composition between roosts. Results showed that Sites 2 and 3 emerged as the most preferred roosting habitats. The model showed that shorebird density peaks when the proportion of bare ground is at 39 % in a roost. Our results showed that different management practices support different shorebird assemblages and highly variable abundance, with the relative proportion of bare ground, water and vegetation as critical factors in the extent to which shorebirds utilize high-tide roots. Continuous management is essential for the long-term success of restoration efforts, contributing to the understanding of sustainable practices in habitat restoration.