Australasian Flyway Research Articles

Multi-scale factors influencing the characteristics of avian communities in urban parks across Beijing during the breeding season.

Understanding the factors that influence the characteristics of avian communities using urban parks at both the patch and landscape level is important to focus management effort towards enhancing bird diversity. Here, we investigated this issue during the breeding season across urban parks in Beijing, China, using high-resolution satellite imagery. Fifty-two bird species were recorded across 29 parks. Analysis of residence type of birds showed that passengers were the most prevalent (37%), indicating that Beijing is a major node in the East Asian–Australasian Flyway. Park size was crucial for total species abundance, but foliage height diversity was the most important factor influencing avian species diversity. Thus, optimizing the configuration of vertical vegetation structure in certain park areas is critical for supporting avian communities in urban parks. Human visitation also showed negative impact on species diversity. At the landscape level, the percentage of artificial surface and largest patch index of woodland in the buffer region significantly affected total species richness, with insectivores and granivores being more sensitive to the landscape pattern of the buffer region. In conclusion, urban birds in Beijing are influenced by various multi-scale factors; however, these effects vary with different feeding types.

The distribution and protection of intertidal habitats in Australia

Shorebirds have declined severely across the East Asian—Australasian Flyway. Many species rely on intertidal habitats for foraging, yet the distribution and conservation status of these habitats across Australia remain poorly understood. Here, we utilised freely available satellite imagery to produce the first map of intertidal habitats across Australia. We estimated a minimum intertidal area of 9856 km2, with Queensland and Western Australia supporting the largest areas. Thirty-nine percent of intertidal habitats were protected in Australia, with some primarily within marine protected areas (e.g. Queensland) and others within terrestrial protected areas (e.g. Victoria). Three percent of all intertidal habitats were protected by both marine and terrestrial protected areas. To achieve conservation targets, protected area boundaries must align more accurately with intertidal habitats. Shorebirds use intertidal areas to forage and supratidal areas to roost, so a coordinated management approach is required to account for movement of birds between terrestrial and marine habitats. Ultimately, shorebird declines are occurring despite high levels of habitat protection in Australia. There is a need for a concerted effort both nationally and internationally to map and understand how intertidal habitats are changing, and how habitat conservation can be implemented more effectively.

A chain is as strong as its weakest link: assessing the consequences of habitat loss and degradation in a long-distance migratory shorebird

The conservation of migratory species represents a major challenge, as they use multiple sites, all contributing in varying degrees in sustaining high survival and reproductive success. There is particular concern for shorebirds of the East Asian—Australasian Flyway (EAAF), where declining numbers of migratory species have mostly been attributed to habitat loss along the East Asian coast. Using a stochastic dynamic programming migration model, we assessed the effect of habitat degradation scenarios along the EAAF on migration behaviour, survival and reproductive success of a long-distance migrating shorebird, the Ruddy Turnstone (Arenaria interpres). Following manipulation of habitat quality through changes in intake rate, we found that changes on the wintering (major non-breeding) ground in South Australia had the highest negative effect on reproductive success and survival. We also identified Taiwan and the Yellow Sea as sites with high importance for reproductive success. Although habitats along the East Asian coastline are currently most threatened from a range of global change processes, we highlight the importance of conserving high-quality shorebird wintering habitat in Australia. This may be of notable importance to trans-equatorial migratory shorebirds, which often make a long non-stop flight from their wintering grounds in order to skip low-latitude sites that typically provide little food.

Continental-scale decreases in shorebird populations in Australia

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.

Temporal patterns of migratory shorebird communities at a stop-over site along the East Asian—Australasian Flyway

Migratory birds face serious time constraints in their life cycles. Species carry on their activities during optimal time windows to maximise their fitness. To understand the temporal patterns of migrating shorebirds, we analysed the pattern of turnover within shorebird communities during northward and southward migration at Chongming Dongtan, a stop-over site in the southern Yellow Sea along the East Asian—Australasian Flyway. Results indicated that temporal patterns in shorebird communities differed between seasons. In the boreal spring, the rate of community turnover was initially slow, then increased rapidly midseason, and finally stabilised. In the boreal autumn, in contrast, the rate of community turnover kept constant. This suggests that shorebird species exhibited more temporal overlap in spring than in autumn, perhaps because time constraints are more severe at breeding than non-breeding grounds. The species sequence was strongly linked with breeding latitude: species that breed farther north occurred at the study site later than those that breed farther south on both northward and southward migration. Moreover, large species were more likely to arrive at the stop-over site early on northward (but not on southward) migration than small species. Integrated with the results from intraspecific studies, we propose that the timing of migration is closely related to the breeding latitude both among and within species.

Movement patterns of Sanderling (Calidris alba) in the East Asian-Australasian Flyway and a comparison of methods for identification of crucial areas for conservation

Worldwide, most populations of migratory shorebirds are in jeopardy, none more so than those of the East Asian—Australasian Flyway (EAAF). In order to preserve these highly mobile species a detailed understanding of their use of feeding and resting sites along the flyway is required. In this study we used light-level geolocators and new analytical tools to reveal individual breeding locations and migration routes of 13 Sanderlings (Calidris alba) that spend their non-breeding season in South Australia. We then used these individual migration routes to identify the timing and location of important stopping areas and compared this with assessments based on resightings of leg-flagged birds and count data. During both northward and southward migration, Sanderlings were found to make extensive use of five main areas of the Chinese coastline, the Yellow Sea and the northern end of the Sakhalin Peninsula. Insights gained from the individual migration routes highlight inherent biases in using only count and resighting data to identify important feeding and resting sites along the Flyway. These findings suggest that data on individual movements may be crucial to effective conservation planning of shorebirds in the EAAF and elsewhere in the world.

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

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.

Declining adult survival of New Zealand Bar-tailed Godwits during 2005–2012 despite apparent population stability

Like many migratory shorebird populations using the East Asian—Australasian Flyway, Bar-tailed Godwits Limosa lapponica baueri in New Zealand have significantly declined since the mid-1990s, but census data indicate a relatively stable population since 2004. The demographic drivers of both the decline and stabilisation remain unknown. We estimated annual survival from mark—recapture data of adult godwits in New Zealand during 2005–2014. Annual adult survival declined over the study period from 0.89-0.96 in 2005–2010 to 0.83-0.84 in 20112012. The simultaneous decline in annual survival found in a separate study of Bar-tailed Godwits L. l. menzbieri in north-west Australia suggests a common effect of their high dependence on threatened migratory staging sites in the Yellow Sea; the more extreme decline in L. l. menzbieri may reflect ecological differences between the populations, such as timing and extent of use of these sites. At current apparent recruitment rates, persistent adult survival of ∼0.84 would lead to a population decline of 5–6% per year in L. l. baueri. Our study implies that the demographic precursors to a population decline developed during a period of apparent population stability; this suggests that monitoring a single index of population stability is insufficient for predicting future trends.

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

SummaryThere 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.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.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.Monitored from 2006–2013, we analysedseasonalapparent 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 knotCalidris canutus piersmai, great knotCalidris tenuirostris,bar‐tailed godwitLimosa 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.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 2012annualapparent 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.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.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 habitat must stop now.

Moorland Point: Decline of a traditional roost-site for Ruddy Turnstone Arenaria interpres, Pacific Golden Plover Pluvialis fulva and other shorebirds in northern Tasmania

The Moorland Point area has been an important high-tide roost for certain migratory shorebird species on the central-north coast of Tasmania, where shorebirds are generally scarce. Ruddy Turnstone Arenaria interpres and Pacific Golden Plover Pluvialis fulva roost on a small rocky headland and adjacent piles of seaweed along with up to three Grey-tailed Tattlers Tringa brevipes (all mainly in summer), and Double-banded Plover Charadrius bicinctus roost above the high-tide mark 250 m to the east (mainly February–early August). More than 300 counts of shorebirds have been made at this site from 1985 to 2014. All these species have declined in recent years. Ruddy Turnstone, Pacific Golden Plover and Grey-tailed Tattler may have been affected by factors elsewhere in the East Asian–Australasian Flyway, but local disturbance is also implicated and needs further management in addition to the recent initiative to block vehicles from the beach. The situation highlights some of the problems in conserving shorebird species that favour scattered small sites and may escape the attention given to sites supporting large numbers of more social shorebirds.

Evolution of the Jiuduansha wetland and the impact of navigation works in the Yangtze Estuary, China

The estuarine wetlands in the Yangtze Estuary face increasing threats due to large-scale engineering projects and huge land requirements. As a Wetland National Nature Reserve and important stopover site for migratory shorebirds of the East Asian–Australasian Flyway, the Jiuduansha wetland, one of four main islands in the estuary, is of both national and international importance. Since 1998 the previously undisturbed wetland has been considerably modified by the adjacent Deep-water Navigation Channel project (DNC). In order to understand the role of the DNC for the evolution of the Jiuduansha wetland, we performed a diagnostic study from multiple perspectives, including deposition rate, area change, evolution track, geometric characteristics, and geomorphological change. By coupling GIS, geostatistics, and remote sensing techniques, this study demonstrates the impact of the DNC on the Jiuduansha wetland in a spatially explicit way. Multi-temporal bathymetric maps and Landsat images from before and after the DNC was constructed were adopted to conduct our study. We find that deposition has occurred in most parts of the wetland over the past almost 30years, accounting for 67.3% of the total area. However, over 40% of the study area shows a decreasing trend in deposition rate. The spatial distribution of deposition–erosion patterns is closely linked to the DNC. We also find that the DNC has substantial effects on the evolution of the Jiuduansha wetland. The 0, 2, and 5m isobaths in the Jiuduansha Shoal (JDS), as well as in the Jiangya Shoal (JYS), the Upper Shoal (US) and the Middle-Lower Shoal (MLS), show different response patterns to the DNC. Specifically, the south training jetty of the DNC has an “adsorption effect” on the JDS above the 2m isobaths intersecting with it. As a result, the evolution track, geometric and geomorphological characteristics of the JDS were markedly altered in the short term. Our comprehensive analysis suggests that in the future, the JDS will become more elongated in both the upstream and downstream direction along the south training jetty, and that the south side of the JDS will be eroded.

The ecology and economics of shorebird conservation in a tropical human‐modified landscape

Summary Rapid and extensive land‐use change in intertidal foraging habitat and coastal roosting habitat is thought to be driving major population declines of shorebirds migrating through the East Asian–Australasian Flyway. Along the Inner Gulf of Thailand, a critical stopover and wintering ground for these birds, artificial wetlands (salt pans and aquaculture ponds) have replaced much of the natural coastal ecosystem. We conducted a two‐part study to (i) assess the importance of salt pans and semi‐traditional aquaculture ponds to shorebirds and (ii) understand the economic forces that drive land‐use change in this region by interviewing salt pan and aquaculture operators. Salt pans provide important roost habitat, particularly for shorter‐legged birds, which are less able to utilize aquaculture ponds due to their greater depth. Moreover, three focal shorebird species foraged extensively in salt pans and semi‐traditional aquaculture ponds, even when intertidal mudflats were exposed, suggesting that artificial wetlands could buffer against the impacts of degraded intertidal foraging areas for some shorebird species. Economic profits from salt production and semi‐traditional aquaculture are similar. Risks to investment and per capita profitability are key factors in determining whether to convert land from one use (e.g. salt pan) to the other (aquaculture). Synthesis and applications. Salt pans provide an important resource to migrating shorebirds. As development pressures increase, operators may need financial incentives if salt pans are to be maintained over large areas. Although semi‐traditional aquaculture is used less by shorebirds, drained ponds provide opportunities to roost and forage. Semi‐traditional aquaculture operators should drain their ponds regularly to provide supplementary habitat for shorebirds. Use of nets and pond liners should be discouraged in both systems. Optimizing aquaculture pond and salt pan management for shorebirds could provide a more pragmatic, cost‐effective and geographically extensive solution to conserving these birds than protected areas alone.

Migratory Waterbirds Response to Coastal Habitat Changes: Conservation Implications from Long-term Detection in the Chongming Dongtan Wetlands, China

Changes in waterbird populations in relation to changes in their habitat are of great concern in the Chongming Dongtan wetlands, one of the most important stopovers for migrating waterbirds in the East Asian–Australasian Flyway. We analyzed the relationship between the changes in the dominant waterbird populations (Charadriidae, Anatidae, Ardeidae, and Laridae) and the changes in their corresponding habitats from 2000 to 2012. In natural wetlands, the species number of Anatidae was significantly positively correlated with the Scirpus mariqueter (hereafter Scirpus) habitat but significantly negatively correlated with the Phragmites australis (hereafter Phragmites) habitat. The densities of Charadriidae and Laridae were both significantly positively correlated with the deep water habitat but significantly negatively correlated with the Spartina alterniflora (hereafter Spartina) habitat. The density of Charadriidae, however, also exhibited significantly positive correlation with the Scirpus habitat. In the aquaculture ponds, the changes in the density of Anatidae in the winter were significantly negatively correlated with the changes in aquaculture ponds. Other waterbirds only exhibited positive or negative correlation trends with their habitats, which did not reach the statistically significant levels. Consequently, changes in waterbird populations are significantly correlated with changes in natural wetlands and aquaculture ponds in the Chongming Dongtan wetlands. Natural wetlands and aquaculture ponds are important to migratory waterbirds during the peak of migration and wintering. Our results promote the development of wetland management strategies for protecting migratory waterbirds in the coastal area of the Yangtze River.

Protecting stopover habitat for migratory shorebirds in East Asia

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.

Threats to the Yellow Sea's Tidal Wetlands

All photographs by Nicholas J. Murray Tidal flats are a highly productive coastal ecosystem with a species diversity thought to rival that of tropical rain forests, yet we know remarkably little about their distribution and status. In East Asia, tidal wetlands are the frontline ecosystem protecting a coastal population of more than 150 million people from storms and sea-level rise. Unprecedented coastal development, particularly in China and South Korea, has led to growing concern about status of coastal wetlands in the region. We developed a new remote sensing method to assess change over >4000 kilometers of the Yellow Sea coastline and discovered vast losses of the region's principal coastal ecosystem, tidal flats, driven primarily by urban, industrial, and agricultural land reclamations. Our methods provide a framework for assessing change of intertidal ecosystems and can be applied to any geographic region with adequate satellite data. Coastal reclamation for industrial development at an offshore island in South Korea; note the ships in port at the top left for scale. East Asia's tidal flats support an annual migration of millions of migratory shorebirds through the East Asian Australasian Flyway. Migratory shorebirds stop in East Asia to rest and refuel, and ongoing habitat loss is likely to severely affect shorebird populations across the flyway. Aquaculture development encroaching ~250 m onto a tidal flat (top of image) in Gomso Bay, South Korea. These photographs illustrate the article “Tracking the rapid loss of tidal wetlands in the Yellow Sea” by Nicholas J. Murray, Robert S. Clemens, Stuart R. Phinn, Hugh P. Possingham, and Richard A. Fuller, published in Frontiers in Ecology and the Environment 12:267–272, June 2014. http://dx.doi.org/10.1890/130260

Loss of periodicity in breeding success of waders links to changes in lemming cycles in Arctic ecosystems

Lemming population cycles in the Arctic have an important impact on the Arctic food web, indirectly also affecting breeding success in Arctic‐nesting birds through shared predators. Over the last two decades lemming cycles have changed in amplitude and even disappeared in parts of the Arctic. To examine the large scale effect of these recent changes we re‐analysed published data from the East Atlantic Flyway (EAF), where a relationship between lemming cycles and wader breeding success was earlier found, and new data on breeding success of waders in the East Asian–Australasian Flyway (EAAF).We found that 1) any long‐term periodicities in wader breeding success existed only until the year 2000 in the EAAF and until the 1980s in the EAF; 2) studying these patterns at a smaller spatial scale, where the Siberian–Alaskan breeding grounds were divided into five geographical units largely based on landscape features, breeding success of waders from the EAAF was not correlated to an index of predation pressure, but positively correlated to Arctic summer temperatures in some species. We argue that fading out of lemming cycles in some parts of the Arctic is responsible for faltering periodicity in wader breeding success along both flyways. These changed conditions have not yet resulted in any marked changing trends in breeding success across years, and declining numbers of waders along the EAAF are therefore more likely a result of changing conditions at stop‐over and wintering sites.

Optimal management of a multispecies shorebird flyway under sea-level rise.

Every year, millions of migratory shorebirds fly through the East Asian-Australasian Flyway between their arctic breeding grounds and Australasia. This flyway includes numerous coastal wetlands in Asia and the Pacific that are used as stopover sites where birds rest and feed. Loss of a few important stopover sites through sea-level rise (SLR) could cause sudden population declines. We formulated and solved mathematically the problem of how to identify the most important stopover sites to minimize losses of bird populations across flyways by conserving land that facilitates upshore shifts of tidal flats in response to SLR. To guide conservation investment that minimizes losses of migratory bird populations during migration, we developed a spatially explicit flyway model coupled with a maximum flow algorithm. Migratory routes of 10 shorebird taxa were modeled in a graph theoretic framework by representing clusters of important wetlands as nodes and the number of birds flying between 2 nodes as edges. We also evaluated several resource allocation algorithms that required only partial information on flyway connectivity (node strategy, based on the impacts of SLR at nodes; habitat strategy, based on habitat change at sites; population strategy, based on population change at sites; and random investment). The resource allocation algorithms based on flyway information performed on average 15% better than simpler allocations based on patterns of habitat loss or local bird counts. The Yellow Sea region stood out as the most important priority for effective conservation of migratory shorebirds, but investment in this area alone will not ensure the persistence of species across the flyway. The spatial distribution of conservation investments differed enormously according to the severity of SLR and whether information about flyway connectivity was used to guide the prioritizations. With the rapid ongoing loss of coastal wetlands globally, our method provides insight into efficient conservation planning for migratory species.

Optimising hydrological conditions to sustain wintering waterbird populations in Poyang Lake National Natural Reserve: implications for dam operations

Summary Poyang Lake is the largest freshwater lake in China and is of global importance for the conservation of migratory waterbirds of the East Asian – Australasian Flyway. Recent dam construction on the Yangtze River and its tributaries for agriculture and hydroelectric power has affected the hydrological regimes in downstream lakes. The Three Gorges Dam changed the hydrological regime of downstream lakes by reducing wet season flooding and expanding water storage in the dry season. Despite the critical role of Poyang Lake in regional and global biodiversity conservation and the potential adverse ecological impacts of the Three Gorges Dam on downstream lakes, there have been few studies of the hydrological requirements of wintering waterbirds in the middle Yangtze floodplains. We assembled a predictor matrix including three hydrological variables (annual inflow, maximum water level in high water season or MaxWL and minimum water level in low water season or MinWL) and two climatic variables (annual rainfall and biological cumulative temperature or BioT). Using the predictor matrix and annual waterbird census, we built group‐specific generalised additive models (GAM) to investigate how waterbird population variations were related to climatic and hydrological factors in the Poyang Lake National Natural Reserve. We then used the modelled predictor–response curves to identify the optimal lake water levels for each waterbird group. The community‐level model selected group and the group‐varying‐coefficient term of BioT, Inflow and MaxWL as explanatory variables. At group level, tuber eaters and sedge foragers responded positively to BioT and MinWL. Seed eaters, invertebrate eaters and fish eaters responded positively to Inflow and negatively to MaxWL and MinWL. Based on the modelled predictor–response curves, we propose the following optimal water level ranges for Poyang Lake wintering waterbird conservation: a) maximum high water season level should be less than 17.4 m; and b) minimum low water level should be between 8.2 m and 8.8 m.

Migratory connectivity magnifies the consequences of habitat loss from sea-level rise for shorebird populations

Sea-level rise (SLR) will greatly alter littoral ecosystems, causing habitat change and loss for coastal species. Habitat loss is widely used as a measurement of the risk of extinction, but because many coastal species are migratory, the impact of habitat loss will depend not only on its extent, but also on where it occurs. Here, we develop a novel graph-theoretic approach to measure the vulnerability of a migratory network to the impact of habitat loss from SLR based on population flow through the network. We show that reductions in population flow far exceed the proportion of habitat lost for 10 long-distance migrant shorebirds using the East Asian-Australasian Flyway. We estimate that SLR will inundate 23-40% of intertidal habitat area along their migration routes, but cause a reduction in population flow of up to 72 per cent across the taxa. This magnifying effect was particularly strong for taxa whose migration routes contain bottlenecks-sites through which a large fraction of the population travels. We develop the bottleneck index, a new network metric that positively correlates with the predicted impacts of habitat loss on overall population flow. Our results indicate that migratory species are at greater risk than previously realized.

Polybrominated diphenyl ethers in birds from Chongming Island, Yangtze estuary, China: Insight into migratory behavior

Sum-PBDEs concentrations in shorebirds and Anatidae ducks muscles from Chongming Dongtan National Nature Reserve ranged from 21–324 to 14–159ngg−1 lw, respectively. PBDEs were detected in muscles of all the studied species. Compared with flyways around the world, migratory waterbirds on the East Asian–Australasian flyway exhibited lower PBDEs burdens than those reported on Black Sea-Mediterranean flyway in Europe and Pacific, Atlantic, Mississippi flyway in North America. Residential Eurasian tree sparrow samples indicated few PBDE products were used in Chongming Island developed in the idea of world famous eco-island. There was no significant difference in PBDEs concentrations between shorebirds and ducks. However, PBDEs composition varied between them. BDE 209 (29–44%) contributed to sum-PBDEs more than BDE 47 (17–19%) in muscles of ducks, while BDE 47 was the predominant congener in shorebirds contributing 32–48%. Stable nitrogen and carbon isotopes and stomach content analysis indicated shorebirds and ducks had the same dietary composition, but showed different preference to bivalves, gastropods and crustaceans for shorebirds and aquatic plant material for ducks. Migratory species had inherent migratory routes and thus had exposure to PBDEs during their stay in breeding grounds, stopover sites and wintering grounds with high use of different commercial PBDE mixtures. Higher percentage of BDE 209 in ducks than shorebirds suggested that breeding ranges and wintering grounds of ducks comprise wetlands in inland and coastal China and Korea where decaBDEs pollution was serious in Asian-Pacific region. Our findings reveal the influence of migratory behavior on PBDEs distribution in migratory waterbirds.