Abstract
Many species depend on multiple habitats at different points in space and time. Their effective conservation requires an understanding of how and when each habitat is used, coupled with adequate protection. Migratory shorebirds use intertidal and supratidal wetlands, both of which are affected by coastal landscape change. Yet the extent to which shorebirds use artificial supratidal habitats, particularly at highly developed stopover sites, remains poorly understood leading to potential deficiencies in habitat management. We surveyed shorebirds on their southward migration in southern Jiangsu, a critical stopover region in the East Asian Australasian Flyway (EAAF), to measure their use of artificial supratidal habitats and assess linkages between intertidal and supratidal habitat use. To inform management, we examined how biophysical features influenced occupancy of supratidal habitats, and whether these habitats were used for roosting or foraging. We found that shorebirds at four of five sites were limited to artificial supratidal habitats at high tide for ~11–25 days per month because natural intertidal flats were completely covered by seawater. Within the supratidal landscape, at least 37 shorebird species aggregated on artificial wetlands, and shorebirds were more abundant on larger ponds with less water cover, less vegetation, at least one unvegetated bund, and fewer built structures nearby. Artificial supratidal habitats were rarely used for foraging and rarely occupied when intertidal flats were available, underscoring the complementarity between supratidal roosting habitat and intertidal foraging habitat. Joined‐up artificial supratidal management and natural intertidal habitat conservation are clearly required at our study site given the simultaneous dependence by over 35,000 migrating shorebirds on both habitats. Guided by observed patterns of habitat use, there is a clear opportunity to improve habitat condition by working with local land custodians to consider shorebird habitat requirements when managing supratidal ponds. This approach is likely applicable to shorebird sites throughout the EAAF.
Highlights
Long‐distance migratory birds, like all migratory species, depend on multiple habitats at different points in space and time
We found that shorebirds at four of five sites were limited to artificial supratidal habitats at high tide for ~11–25 days per month because natural intertidal flats were completely covered by seawater
The annual survival of Red Knot Calidris canutus rufa in North America is linked to the spawning abun‐ dance of horseshoe crabs at the midpoint of their annual migration (McGowan et al, 2011) and female American Redstarts Setophaga ruticilla that occupy high‐quality nonbreeding habitat in Central and South America produce more young on their breeding grounds in Canada (Norris et al, 2004)
Summary
Long‐distance migratory birds, like all migratory species, depend on multiple habitats at different points in space and time. In the EAAF, the scale and rate of intertidal habitat loss and degradation in Yellow Sea staging areas (Melville, Chen, & Ma, 2016; Murray, Clemens, Phinn, Possingham, & Fuller, 2014) are well accepted as the primary driver of severe population declines in multiple shorebird species (Amano, Székely, Koyama, Amano, & Sutherland, 2010; Piersma et al, 2016 Studds et al, 2017) This conservation crisis has prompted a focussed research effort to highlight negative consequences of coastal devel‐ opment and armouring on migratory waterbirds and the need to halt intertidal habitat loss (Choi et al, 2018; Ma et al, 2014; Murray, Ma, & Fuller, 2015; Piersma et al, 2017; Yang et al, 2011). We conclude by exploring potential approaches to im‐ plementing supratidal habitat management in Rudong for the benefit of migratory shorebirds, and the applicability of our results to other sites
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