The conservation of migratory shorebirds needs to account for the different habitat selection patterns across species and between day and night

Migratory shorebirds are experiencing rapid population decline. Monitoring programs along shorebird flyways provide information on their population dynamics and habitat requirements at different life stages, which is important for conservation plans. Such surveys often occur at several high-tide roosts during daytime high tide, when birds are more concentrated and easier to count. However, it remains unclear whether these surveys can cover the entire shorebird community within a site and represent shorebirds' preferences during both day and night. Here, we tested two community-level hypotheses: 1) surveys at high-tide roosts can adequately represent the community within a site; and 2) daytime surveys can adequately represent birds' preferences over the whole day, by combining GPS tracking data of four species – nine common redshanks ( Tringa totanus ), three grey plovers ( Pluvialis squatarola ), two greater sand plovers ( Charadrius leschenaultii ) and two red knots ( Calidris canutus ) – with community-level shorebird survey data in aquaculture ponds and nearby tidal flats on their overwintering grounds in southern China. Our results showed that in an area with extensive artificial roosting habitats, shorebirds using the same feeding area on the tidal flat may choose different roosts, even when alternative roosts are available nearby. Individuals within the three tracked species exhibited marked differences in roost selection between daytime and night, and the factors influencing roost selection varied both among species and between day and night. Therefore, daytime high-tide surveys alone are insufficient to assess habitat use and preferences at the species level. Management of shorebird roosting habitats should not assume uniform preferences across species.