Simultaneous declines in summer survival of three shorebird species signals a flyway at risk

摘要

There is increasing concern about the world’s animal migrations. With many land-use andclimatological changes occurring simultaneously, pinning down the causes of large-scale conservationproblems requires sophisticated and data-intensive approaches.2. Declining shorebird numbers along the East Asian–Australasian Flyway, in combinationwith data on habitat loss along the Yellow Sea (where these birds refuel during long-distancemigrations), indicate a flyway under threat.3. If habitat loss at staging areas indeed leads to flyway-wide bird losses, we would predictthat: (i) decreases in survival only occur during the season that birds use the Yellow Sea, and(ii) decreases in survival occur in migrants that share a reliance on the vanishing intertidalflats along the Yellow Sea, even if ecologically distinct and using different breeding grounds.4. Monitored from 2006–2013, we analysed seasonal apparent survival patterns of threeshorebird species with non-overlapping Arctic breeding areas and considerable differences inforaging ecology, but a shared use of both north-west Australian non-breeding grounds andthe Yellow Sea coasts to refuel during northward and southward migrations (red knot Calidriscanutus piersmai, great knot Calidris tenuirostris, bar-tailed godwit Limosa lapponicamenzbieri). Distinguishing two three-month non-breeding periods and a six-month migrationand breeding period, and analysing survival of the three species and the three seasons in asingle model, we statistically evaluated differences at both the species and season levels.5. Whereas apparent survival remained high in north-west Australia, during the time awayfrom the non-breeding grounds survival in all three species began to decline in 2011, havinglost 20 percentage points by 2012. By 2012 annual apparent survival had become as low as0?71 in bar-tailed godwits, 0?68 in great knots and 0?67 in red knots. In a separate analysisfor red knots, no mortality occurred during the migration from Australia to China. In thesummers of low summer survival, weather conditions were benign in the Arctic breedingareas.6. We argue that rapid seashore habitat loss in the Yellow Sea is the most likely explanation ofreduced summer survival, with dire (but uncertain) forecasts for the future of these flyway populations.This interpretation is consistent with recent findings of declining shorebird numbers atseemingly intact southern non-breeding sites.7. Policy implications. Due to established economic interests, governments are usually reluctantto act for conservation, unless unambiguous evidence for particular cause–effect chainsis apparent. This study adds to an increasing body of evidence that habitat loss along theYellow Sea shores explains the widespread declines in shorebird numbers along the EastAsian–Australasian Flyway and threatens the long-term prospects of several long-distancemigrating species. To halt further losses, the clearance of coastal intertidal habitat must stop now.