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

Abstract

Summary1. 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 0Á71 in bar-tailed godwits, 0Á68 in great knots and 0Á67 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. 2016, 53, 479-490 doi: 10.1111/1365-2664.12582 7. Policy implications. Due to established economic interests, governments are usually reluctant to act for conservation, unless unambiguous evidence for particular cause-effect chains is apparent. This study adds to an increasing body of evidence that habitat loss along the Yellow Sea shores explains the widespread declines in shorebird numbers along the East Asian-Australasian Flyway and threatens the long-term prospects of several long-distance migrating species. To halt further losses, the clearance of coastal intertidal habita...

Shorebirds along the Yellow Sea coast of China face an uncertain future—a review of threats

“…The current loss of intertidal habitats has resulted in increasing concentrations of birds at the remaining sites (Yang et al 2011) and is thought to be already adversely affecting shorebird populations (Conklin et al 2016;Piersma et al 2016). Significant further loss of habitat are already included in provincial development plans, but not all have yet been approved by the State Council (see above).…”

“…Murray et al (2014) estimate the area of China's tidal flats were~5398 km 2 in the 1950s,~2677 km 2 in the 1980s and, by the 2000s, had decreased to 1611 km 2 , with the average annual rate of loss since the 1980s being 1.8% per annum (p.a.) Piersma et al (2016), however, report an annual loss of 4% between 1990 and 2013. Nevertheless, the rate of loss is increasing; rates of land claim, which were~400 km 2 p.a.…”

Seabirds? : what seabirds? : An exploratory study into the origin of seabirds visiting the SE North Sea and their survival bottlenecks

“…The effects of a specific human-induced mortality, such as the effects of an oil spill (Votier et al (2005), or of habitat degradation in a specific part of their range Piersma et al (2015) can be modelled if sufficient data are available for the impacted population. Ideally, large numbers of individually marked birds are followed over their entire life, either through electronic tagging or by applying permanent marks that can be read from a distance, such as colour rings, or by standard, steel rings.…”

Ecology and conservation of Australia’s shorebirds

“…Iwamura et al (2013) showed how a 30% loss of habitat in coastal areas such as East Asia's Yellow Sea might result in as much as a 70% decline in some shorebird populations due to the large percentage of some populations reliant on those habitats during migration. There is little doubt that the most pressing conservation need for migratory shorebirds reliant on coastal staging habitats in the EAAF is to ensure adequate protections for the remaining important coastal staging habitats in east Asia which are being lost at alarming rates (MacKinnon et al, 2012;Murray et al, 2014;Piersma et al, 2015). However, several shorebird species migrate across a broad front and use a wide variety of wetland habitats (Boere & Stroud, 2006;Hagemeijer, 2006), and conserving them requires broader strategies that account for the irregularity in suitability of many inland wetlands (Skagen & Knopf, 1993;Haig et al, 1998).…”