Migratory animals are threatened by human-induced global change. However, little is known about how stopover habitat, essential for refuelling during migration, affects the population dynamics of migratory species. Using 20 years of continent-wide citizen science data, we assess population trends of ten shorebird taxa that refuel on Yellow Sea tidal mudflats, a threatened ecosystem that has shrunk by >65% in recent decades. Seven of the taxa declined at rates of up to 8% per year. Taxa with the greatest reliance on the Yellow Sea as a stopover site showed the greatest declines, whereas those that stop primarily in other regions had slowly declining or stable populations. Decline rate was unaffected by shared evolutionary history among taxa and was not predicted by migration distance, breeding range size, non-breeding location, generation time or body size. These results suggest that changes in stopover habitat can severely limit migratory populations.

/pdf/rapid-population-decline-in-migratory-shorebirds-relying-on-42pjq80d85.pdf

Rapid population decline in migratory shorebirds relying on Yellow Sea tidal mudflats as stopover sites

Summary 1. There is increasing concern about the world’s animal migrations. With many land-use and climatological changes occurring simultaneously, pinning down the causes of large-scale conservation problems requires sophisticated and data-intensive approaches. 2. Declining shorebird numbers along the East Asian–Australasian Flyway, in combination with data on habitat loss along the Yellow Sea (where these birds refuel during long-distance migrations), indicate a flyway under threat. 3. If habitat loss at staging areas indeed leads to flyway-wide bird losses, we would predict that: (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 intertidal flats 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 three shorebird species with non-overlapping Arctic breeding areas and considerable differences in foraging ecology, but a shared use of both north-west Australian non-breeding grounds and the Yellow Sea coasts to refuel during northward and southward migrations (red knot Calidris canutus piersmai, great knot Calidris tenuirostris, bar-tailed godwit Limosa lapponica menzbieri). Distinguishing two three-month non-breeding periods and a six-month migration and breeding period, and analysing survival of the three species and the three seasons in a single 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 away from the non-breeding grounds survival in all three species began to decline in 2011, having lost 20 percentage points by 2012. By 2012 annual apparent survival had become as low as 0� 71 in bar-tailed godwits, 0� 68 in great knots and 0� 67 in red knots. In a separate analysis for red knots, no mortality occurred during the migration from Australia to China. In the summers of low summer survival, weather conditions were benign in the Arctic breeding areas. 6. We argue that rapid seashore habitat loss in the Yellow Sea is the most likely explanation of reduced 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 at seemingly intact southern non-breeding sites.

/pdf/simultaneous-declines-in-summer-survival-of-three-shorebird-25blz2dua7.pdf

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

Decreases in shorebird populations are increasingly evident worldwide, especially in the East Asian-Australasian Flyway (EAAF). To arrest these declines, it is important to understand the scale of both the problem and the solutions. We analysed an expansive Australian citizen-science dataset, spanning the period 1973 to 2014, to explore factors related to differences in trends among shorebird populations in wetlands throughout Australia. Of seven resident Australian shorebird species, the four inland species exhibited continental decreases, whereas the three coastal species did not. Decreases in inland resident shorebirds were related to changes in availability of water at non-tidal wetlands, suggesting that degradation of wetlands in Australia's interior is playing a role in these declines. For migratory shorebirds, the analyses revealed continental decreases in abundance in 12 of 19 species, and decreases in 17 of 19 in the southern half of Australia over the past 15 years. Many trends were strongly associated with continental gradients in latitude or longitude, suggesting some large-scale patterns in the decreases, with steeper declines often evident in southern Australia. After accounting for this effect, local variables did not explain variation in migratory shorebird trends between sites. Our results are consistent with other studies indicating that decreases in migratory shorebird populations in the EAAF are most likely being driven primarily by factors outside Australia. This reinforces the need for urgent overseas conservation actions. However, substantially heterogeneous trends within Australia, combined with declines of inland resident shorebirds indicate effective management of Australian shorebird habitat remains important.

/pdf/continental-scale-decreases-in-shorebird-populations-in-2ra705feoa.pdf

Continental-scale decreases in shorebird populations in Australia

Saemangeum, in the Republic of Korea (ROK, commonly called South Korea) was one of the most important shorebird staging sites in the Yellow Sea. It supported at least 330000 shorebirds annually between 1997 and 2001, including ~30% of the world population of Great Knots (Calidris tenuirostris) during both northward and southward migration. Construction of a 33-km long sea-wall was completed in April 2006. We show that shorebird numbers at Saemangeum and two adjacent wetlands decreased by 130000 during northward migration in the next two years and that all species have declined at Saemangeum since completion of the sea-wall. Great Knots were among the most rapidly affected species. Fewer than 5000 shorebirds were recorded at Saemangeum during northward migration in 2014. We found no evidence to suggest that most shorebirds of any species displaced from Saemangeum successfully relocated to other sites in the ROK. Instead, by 2011–13 nearly all species had declined substantially in the ROK since previous national surveys in 1998 and 2008, especially at more heavily reclaimed sites. It is likely that these declines were driven by increased mortality rather than movement to alternate staging sites given that other studies have shown concurrent declines in numbers and survival on the non-breeding grounds. This is the first study in the East Asian–Australasian Flyway to confirm declines of shorebirds at a range of geographical scales following a single reclamation project. The results indicate that if migratory shorebirds are displaced from major staging sites by reclamation they are probably unable to relocate successfully to alternate sites.

/pdf/reclamation-of-tidal-flats-and-shorebird-declines-in-2ftplnw3sh.pdf

Reclamation of tidal flats and shorebird declines in Saemangeum and elsewhere in the Republic of Korea

Many migratory species depend on staging sites at which they refuel while on migration, and effective protection of such habitats is crucial to their conservation. Here we investigate the extent to which protected areas cover and ameliorate loss of tidal flats in East Asia, the key staging habitat for threatened and declining shorebirds migrating through the East Asian–Australasian Flyway. We discover rapid losses of the tidal flat ecosystem both inside (−0.42 % year−1) and outside (−0.89 % year−1) protected areas. In China, tidal flats are well represented within protected areas (22.9 % of current tidal flats occur within protected areas), but habitat loss continued despite protection (−0.55 % year−1 inside, −0.97 % year−1 outside). By contrast, in South Korea, where 12.1 % of remaining tidal flat is in protected areas, the rate of habitat loss outside protected areas was the highest in our study region (−1.83 % year−1), yet inside protected areas there was tidal flat aggradation (+1.13 % year−1), indicating either that protected area placement is biased away from vulnerable habitats, or protected areas are highly effective in South Korea. Tidal flats across our study area were lost most rapidly in internationally important sites for migratory shorebirds (−1.66 % year−1), suggesting that transformative land use change of coastal areas is occurring disproportionately in regions that are important for migratory birds. We urge (1) improved management of existing protected areas in East Asia, particularly in China, (2) targeted designation of new protected areas in sites crucial for supporting migratory birds and (3) integrated decision-making that simultaneously plans for coastal development and coastal conservation.

Protecting stopover habitat for migratory shorebirds in East Asia

Corner Inlet, Victoria, provides habitat for one of the largest and most diverse assemblages of shorebirds in southern Australia. Systematic counting commenced in 1981 and has continued, uninterrupted, to the present (2011). Standardised counts, along fixed boat routes, indicate that numbers in summer of all species combined have declined by 23% over the 30 year count period, from typically 35-40,000 in the earlier years to 25-30,000 in recent times. Ten species - Grey Plover Pluvialis squatarola, Ruddy Turnstone Arenaria interpres, Eastern Curlew Numenius madagascariensis, Red Knot Calidris canutus, Great Knot Calidris tenuirostris, Curlew Sandpiper Calidris ferruginea, Sharp-tailed Sandpiper Calidus acuminata, Common Greenshank Tringa nebularia, Greater Sand Plover Charadrius leschenaulti, and Lesser Sand Plover C. mongolus - have declined, while Sooty Oystercatcher Haematopus fuliginosus, has increased. Numbers of five other migratory species -Bar-tailed Godwit Limosa lapponica, Whimbrel Numenius phaepus, Red-necked Stint Calidris ruficollis, Sanderling C. alba and Double-banded Plover Charadrius bicinctus and one resident, species, Australian Pied Oystercatcher Haematopus longirostris - have not shown any significant change. Estimated declines in the abundance of individual species ranged from 47% to 95%. In contrast there was a significant increase in Sooty Oystercatchers of between 1.5 fold (winter) and 3.5 fold (summer). Numbers counted varied widely between years, most likely due to a combination of annual variation in demographic parameters, and possibly detection rates. The cause of longterm changes in abundance at Corner Inlet is not certain, but habitat destruction in staging areas, notably the Yellow Sea regions of China and Korea, is suggested as the main contributor with related changes in adult survival rates a more likely mechanism than changes in breeding success. Interestingly, declines in several species were most pronounced over one or two years. This study emphasises the benefit of using the same route and observers over long periods to identify trends in abundance.

Trends of shorebirds in corner inlet, victoria, 1982-2011

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Trends of shorebirds in corner inlet, victoria, 1982-2011