East Asian-Australasian Flyway Research Articles

Effects of constant high water levels in winter on waterbird diversity in Caizi Lakes: A functional perspective

The middle and lower Yangtze River floodplain lakes are important stopover and wintering sites for migratory birds on the East Asian–Australasian Flyway. The periodic water level fluctuation of the lakes plays a critical role in the aggregation of waterbirds. However, the construction of a series of gates and dams has impeded the hydrological connectivity between rivers and lakes and disrupted the natural water level fluctuation patterns of lakes. The water level status of lakes influences determines their habitat utilization by waterbirds. In recent years, Caizi Lakes, the gate-controlled lake connected to the Yangtze River due to the need for water level regulation requirements, has experienced sustained high water levels in winter, which can reduce habitat quality and in turn influence waterbirds activity. In the present study, wintering waterbirds in Caizi Lakes were surveyed during the 2021–2022 (W1) and 2022–2023 (W2) wintering periods. Moreover, we explored the effects of constant high water levels in winter on waterbird assemblages we explored by comparing species richness, abundance, and functional waterbird diversity. Correlation analyses were then performed to elucidate the relationship between habitat factors and water level changes during the wintering period of migratory birds and between changes in various habitat factors and wintering waterbird assemblages under different hydrological conditions. The results showed that functional beta diversity was more sensitive to changes in waterbird assemblages in Caizi Lakes than functional alpha diversity. Moreover, constant high water levels in the mid-wintering period decreased suitable habitats for wintering waterbirds, increased functional turnover among waterbird assemblages, increased total dissimilarity among assemblages significantly, and decreased the level of functional nestedness significantly. Additionally, the areas of the three wetland habitats in Caizi Lakes were significantly correlated with water level changes during W1 and relatively less affected by water level changes under constant high water level conditions during W2. The changes in habitat area were influenced primarily by anthropogenic activities, with an increase in meadow area favorable for assemblage species richness and abundance, as well as functionally nested components. Water level regulation should take into consideration the natural hydrological rhythms of the declining water level to ensure that adequate and suitable habitats are provided for wintering waterbirds.

Assessment of Waterbird Habitat Importance and Identification of Conservation Gaps in Anhui Province.

Wetlands are among the most important habitats of highly wetland-dependent waterbirds but are subject to ongoing habitat loss and degradation owing to intensified anthropogenic activities. The scarcity of human and natural resources makes effective habitat protection an important concern. Here, we aimed to investigate waterbird habitat protection methods for Anhui Province, China, a critical stopover and wintering area on the East Asian-Australasian Flyway that features rich wetland resources subject to significant habitat loss and degradation. We evaluated the status and importance of 306 wintering waterbird habitats and identified the key environmental influences and current protection gaps using the entropy weights method and generalized additive modeling. We found 73 important habitats for waterbirds in Anhui Province, which were classified into levels of importance (descending from I to V) according to the natural discontinuity method. Level I and Level II habitats were mainly located in the Yangtze River floodplain and Level IV habitats in the Huaihe River floodplain. The gap analysis showed that 42 important waterbird habitats had protection gaps, accounting for 57.53% of the total area. Waterbird habitat importance was significantly correlated with elevation, normalized vegetation index, lake area, and lake circumference but not with distance from roads or population density. The results of this study provide scientific information for waterbird habitat conservation planning, which is crucial for maintaining wetland ecosystem functions.

Effects of Invasive Smooth Cordgrass Degradation on Avian Species Diversity in the Dafeng Milu National Nature Reserve, a Ramsar Wetland on the Eastern Coast of China

Invasive smooth cordgrass (Spartina alterniflora) has been expanding rapidly through the coastal wetlands of eastern China and these changes negatively affect local birds. In the Dafeng Milu National Nature Reserve (henceforth referred to as DMNNR), rapid degradation of spartina occurs after an increase in milu (Elaphures davidianus; hereafter elk) numbers and ecological hydrological engineering. We evaluated the impact of such degradation on the abundance and species diversity of birds in the DMNNR during 2017–2021. We found that the area covered by S. alterniflora decreased significantly in the study area at a rate of 310 ha per year and by 62% during 2017–2021 (p < 0.01). With this decrease in the S. alterniflora area, the species richness and abundance of birds first increased and then decreased. Songbird density clearly decreased but species richness did not significantly do so. This research demonstrated that during the initial stages of vegetation degradation, there was a positive effect on bird diversity. With the increasing vegetation degradation increases, both songbirds and waterbirds experience negative impacts. The DMNNR is an important stopover site for waterbirds in the East Asian–Australasian Flyway, and additional measures are needed to control vegetation degradation and to restore the native habitats for birds.

Prioritizing landscapes for mitigating the impacts of onshore wind farms on multidimensional waterbird diversity in the Yellow Sea

Abstract Ongoing wind energy developments play a key role in mitigating the global effects of climate change and the energy crisis; however, they have complex ecological consequences for many flying animals. The Yellow Sea coast is considered as an ecological bottleneck for migratory waterbirds along the East Asian–Australasian flyway (EAAF), and is also an important wind farm base in China. However, the effects of large-scale onshore wind farms along the EAAF on multidimensional waterbird diversity, and how to mitigate these effects, remain unclear. Here we examined how wind farms and their surrounding landscapes affected multidimensional waterbird diversity along the Yellow Sea coast. Taxonomic, functional, and phylogenetic diversity of the waterbird assemblages, and mean pairwise distances and nearest taxon distances with null models were quantified in relation to 4 different wind turbine densities. We also measured 6 landscape variables. Multi-dimensional waterbird diversity (taxonomic, functional, and phylogenetic diversity) significantly decreased with increasing wind turbine density. Functional and phylogenetic structures tended to be clustered in waterbird communities, and environmental filtering drove waterbird community assemblages. Furthermore, waterbird diversity was regulated by a combination of wind turbine density and landscape variables, with edge density of aquaculture ponds, in addition to wind turbine density, having the greatest independent contribution to waterbird diversity. These results suggest that attempts to mitigate the impact of wind farms on waterbird diversity could involve the landscape transformation of wind farm regions, for example, by including high-edge-density aquaculture ponds (i.e., industrial ponds) around wind farms, instead of traditional low-edge-density aquaculture ponds.

Tracking the 2D/3D Morphological Changes of Tidal Flats Using Time Series Remote Sensing Data in Northern China

Tidal flats in northern China are essential parts of the East Asian-Australasian Flyway, the densest pathway for migratory waterbirds, and are of great ecological and economic importance. They are threatened by human activities and climate change, raising the urgency surrounding tracking the spatiotemporal dynamics of tidal flats. However, there is no cost-effective way to map morphological changes on a large spatial scale due to the inaccessibility of the mudflats. In this study, we proposed a pixel-based multi-indices tidal flat mapping algorithm that precisely characterizes 2D/3D morphological changes in tidal flats in northern China using time-series remote sensing data. An overall accuracy of 0.95 in delineating tidal flats to a 2D extent was achieved, with 11,716 verification points. Our results demonstrate that the reduction in sediment discharge from rivers along the coastlines of the Yellow and Bohai Seas has resulted in an overall decline in the area of tidal flats, from 4856.40 km2 to 4778.32 km2. Specifically, 3D analysis showed that significant losses were observed in the mid-to-high-tidal flat zones, while low-elevation tidal flats experienced an increase in area due to the transformations in mid-to-high-tidal flats. Our results indicate that the sediment inputs from rivers and the succession of native vegetation are the primary drivers leading to 2D/3D morphological changes of tidal flats following the cessation of extensive land reclamation in northern China.

Wild Bird-Origin H6N2 Influenza Virus Acquires Enhanced Pathogenicity after Single Passage in Mice.

The H6 subtype of avian influenza viruses (AIVs) has emerged as one of the predominant subtypes in both wild and domestic avian species. Currently, H6 AIVs have acquired the ability to infect a wide range of mammals, though the related molecular mechanisms have yet to be fully investigated. In this study, a wild bird-origin H6N2 AIV was isolated from the East Asian-Australasian migratory flyway region located in Liaoning Province. This H6N2 virus initially expressed limited replication in mice. However, after one passage in mice, the virus acquired two mutations, PB2 E627K and HA A110V. The mutant displayed enhanced replication both in vitro and in vivo, proving lethal to mice. But the mutant retained the α-2, 3-linked sialic acid binding property and failed to transmit in guinea pigs. We explored the molecular mechanisms underlying the pathogenicity difference between the wild type and the mutant. Our findings revealed that PB2 E627K dramatically enhanced the polymerase activity of the H6N2 virus, while the HA A110V mutation decreased the pH of HA activation. This study demonstrated that the H6N2 subtype wild bird-origin AIV easily acquired the mammalian adaptation. The monitoring and evaluation of H6 wild bird-origin AIV should be strengthened.

Running the gauntlet; flyway-wide patterns of pollutant exposure in blood of migratory shorebirds

Shorebirds (order Charadriiformes) are among the world's most threatened avian taxa. Within the East Asian-Australasian Flyway (EAAF), a major threat to shorebirds' survival may be the gauntlet of pollution along the flyway. Metals, persistent organic pollutants (POPs), and per-/polyfluoroalkyl substances (PFASs) persist in the environment to the detriment of wildlife. In this study, we analysed element and PFAS concentrations in blood from 142 individuals across six species of Arctic-breeding migratory shorebirds with contrasting population trends, to discern species- and site-specific pollution differences, and determine how pollution correlated with population trends of EAAF shorebirds. Potential within-year pollution variations were investigated by blood-sampling birds at two sites, representing different points in the birds' annual migrations: staging in Taiwan on southward migrations and at non-breeding grounds in Western Australia (WA). Species' pollutant concentrations were compared to established population trends. Concentrations of potentially toxic elements were low in most individuals regardless of species. PFASs (range: <0.001–141 ng/g), Hg (<0.001–9910 ng/g) and Pb (<0.01–1210 ng/g) were higher in Taiwan than in WA (PFAS Taiwan median: 14.5 ng/g, WA median: 3.45 ng/g; Hg Taiwan: 338 ng/g, WA: 23.4 ng/g; Pb Taiwan: 36.8 ng/g, WA: 2.26 ng/g). Meanwhile As (range <0.001–8840 ng/g) and Se (290–47600 ng/g) were higher in WA than Taiwan (As Taiwan median: 500 ng/g, WA median: 1660 ng/g; Se Taiwan: 5490 ng/g, Se WA: 23700 ng/g). Nevertheless, pollutant concentrations in a subset of individuals may exceed sublethal effect thresholds (As, Se and PFASs). Finally, we found no consistent differences in pollution among species and demonstrated no correlation between pollution and population trends, suggesting pollution is likely not a major driver for population declines of EAAF shorebirds. However, ongoing and locally heavy environmental degradation and exposure to other contaminants not investigated here, such as POPs, warrants continued consideration when managing EAAF shorebird populations.

Biometric variability and sexual size dimorphism in the Great Knot Calidris tenuirostris

The Great Knot is a species from the Scolopacidae family of waders migrating within the East Asian-Australasian Flyway, and studies on this species have contributed greatly to understanding of migration ecophysiology and migration strategies in long-distance migrants. In this paper, we provide the first description of biometric variability and sexual size dimorphism in Great Knots. During the study on the Kamchatka Peninsula, 683 adults and 229 juveniles were measured and sexed molecularly. In adults, the mean measurements of females were larger than in males, except for tarsus length. In juveniles, at the early stage of migration from breeding to wintering grounds, apparently growth was not complete. Sexual dimorphism was small, with only wing length being significantly longer in females than in males. All dimensions of juveniles were smaller than those of adults, especially in bill length. The most sexually dimorphic trait in both adults and juveniles was wing length, and the most effective discriminant function with wing length as a single predictor correctly identified the sex of 76% of birds in both age classes. However, molecular sexing is the method of choice for reliable sexing, especially in juveniles.

It takes two to Tango: Plant height and nutrient level determine the diet selection of wintering geese in Poyang Lake, a Ramsar wetland

In Poyang Lake, the largest and one of the most important wintering sites in the East Asian-Australasian Flyway, Carex (Carex cinerascens Kük) meadows provide the primary food source for the wintering geese. However, due to intensified river regulation and more frequent extreme climatic events such as drought, observational evidence suggests that the synchrony of geese migration and Carex phenology could not be maintained without human interventions, imposing a great risk of food shortage during the wintering period. Consequently, the current conservation priority in this Ramsar site is shifted to wet meadow improvement to ensure optimal food quality. Understanding the food preferences of wintering geese is the key for effective wet meadow management. As the growth stage and nutrient level of food plants are the decisive factors influencing the diet selection of herbivores, in this study, we sampled the preferred food items by tracking the foraging paths of the Greater White-fronted Goose (n = 84) and Bean Goose (n = 34) to quantify the “foraging window” in terms of plant height,protein level, and energy content. Further, we established relationships between the above three variables of Carex based on in-situ measurements. The results show that the geese prefer plants with height ranging from 2.4 to 25.0 cm, with protein content from 13.9 to 25.2 %, and energy content from 1440.0 to 1813.6 KJ/100 g. While plant energy content increases with height, the height-protein level relationship is negative. The opposite growth curves signify a conservation challenge to maintain the delicate balance between the quantity and quality requirements of wintering geese. Carex meadow management, such as mowing, should focus on optimizing the timing of action to maximize energy supply while maintaining the right protein level for the long-term fitness, reproduction and survival of the birds.

Identifying research trends in avian migration tracking in Korea using text mining

Identifying avian migration routes and habitats is critical for species conservation and management. South Korea is an important region in the East Asian-Australasian flyway, inhabited by various migratory birds. In this study, previous research on avian migration routes in South Korea was systematically analyzed, and research trends and characteristics were determined. Among 64 peer-reviewed papers, the number of papers by year has gradually increased since the 2000s. Land birds were the most extensively studied, followed by wading birds, raptors, waterfowl, multiple waterbird groups, and shorebirds. Among the research methods, wildlife tracking devices were most commonly used (n = 32), followed by direct visual observation (n = 19), bird banding (n = 10), and stable isotope analysis (SIA; n = 3). Sinan-gun, a Korean island, received the greatest attention; several studies have been conducted across various regions throughout South Korea. Text mining showed that the following terms were frequently used and strongly correlated: ‘home’, ‘range’, ‘breeding’, ‘wintering’, ‘island’, ‘area’, and ‘habitat’. Based on our findings, we predict that, as technology advances, the number of studies on migration routes of a greater diversity of species using global positioning system (GPS) tracking and SIA will continue to increase.

Identifying shorebird conservation hotspots and restoration gaps in stopover sites: A perspective of ‘ecologically linked’ habitats

Shorebird populations are declining around the world, which has prompted concerns regarding tidal flat protection during migration. The lack of high-tide roosts not only can limit the access of shorebirds to tidal flats but also means that they expend more energy when moving between tidal flats and roosting sites. This situation can negatively affect their body condition. This highlights the importance of maintaining a network of tidal flats and high-tide roosts “ecologically linked” by shorebirds. Using the Yellow River Delta (YRD), a key stopover site in the East Asian–Australasian Flyway (EAAF), as the case study area, we assessed how the availability of optimal high-tide roosts has changed over time and identified conservation hotspots and restoration gaps from the perspective of ecological connectivity for shorebirds. Based on a developed Geographic Information System (GIS) method, combined with knowledge of shorebird roost choices from the literature and remote sensing data, we evaluated the adequacy of high-tide roosts in the YRD over 20 years (2000–2020) and identified restoration areas by scenario analysis. The results showed that 1) the mean distance between potential intertidal habitats and the nearest optimal high-tide habitat increased from 1305 m in 2000 to 2931 m in 2020, with a 30 % decline in the area of intertidal habitats suitably covered by optimal high-tide habitats for shorebirds in Group 1 (body length ≦ 20 cm) in the YRD; 2) the scenario analysis suggested that this gap can be eliminated by seasonal management of mariculture ponds and salt pans in key areas. This approach is likely applicable to stopover sites throughout the EAAF.

Protecting China's major urban bird diversity hotspots.

The Kunming-Montreal Global Biodiversity Framework puts forward a new conservation target to enhance urban biodiversity. Cities have a great potential for sustaining biodiversity and nurturing a healthy relationship between people and our nearest nature. It is especially important in developing countries such as China, which has a rich biodiversity and a rapidly growing urban population. Using citizen science data, we show that 48% of the national bird diversity and 42% of its threatened species have been recorded in the top-20 most avian-diverse cities of China. Urban bird diversity hotspots clustered along the eastern coast, indicating the importance of establishing an inter-city conservation network along the East Asian-Australasian Flyway. This urban conservation network would be a starting point to promote social recognition of biodiversity's relational value in a country with a vast population and an increasingly important role in meeting UN's Sustainable Development Goals.

Conservation of Bewick’s swans (Cygnus columbianus bewickii): Insights from the identification of critical stopover sites and migration corridors

Migratory birds face diverse threats during migration. Critical stopover sites (CSSs) are essential refueling and resting sites for migratory birds that ensure their complete migration and survival. Therefore, identifying bird migration patterns, routes, and critical habitats is vital for conservation. From 2018–2022, we deployed satellite tracking devices on 30 Bewick’s swans (Cygnus columbianus bewickii) wintering in China to determine their migration routes. Using a dynamic Brownian bridge movement model, we identified migration corridors, core movement areas, and CSSs for Bewick’s swans. Combining protected area databases and human settlement types, we further assessed the swans’ conservation status and human impacts on CSSs. The results showed that Bewick’s swans migrated north from their wintering grounds using one of three routes (west, middle, and east), passing through Mongolia to reach the Russian Arctic (breeding grounds) in spring. They followed similar routes during autumn to return to wintering grounds. We found a new middle route within the East Asian–Australasian Flyway (EAAF) and several northward expanded wintering sites. Our study revealed similarities and differences in the spring and autumn migrations, with longer stopover durations in spring due to migration strategies and ice conditions. Moreover, our findings identified the Inner Mongolia region, the Songnen Plain, the Bohai Rim of China, and the main streams of the Lena River and the Ob River of Russia as CSSs for Bewick’s swans. However, the conservation status of the CSSs was relatively low; and the situation was more severe in spring than in autumn, only 4.3% of the total area was protected, likely due to the distribution of farmland and urban areas. Specifically, 14.3% of the CSSs in China were in urban areas during spring, while in Mongolia and Russia this figure was less than 1%. Therefore, it is necessary to balance waterbird conservation with sustainable agriculture and urban development. This research contributes to our understanding of the migratory ecology of Bewick’s swans wintering in China. The identified migration corridors and CSSs are crucial for the future conservation of swans along the EAAF.

Importance of habitat heterogeneity in tidal flats to the conservation of migratory shorebirds.

Understanding species distribution patterns and what determines them is critical for effective conservation planning and management. In the case of shorebirds migrating along the East Asian-Australasian Flyway (EAAF), the loss of stopover habitat in the Yellow Sea region is thought to be the primary reason for the precipitous population declines. However, the rates of decline vary considerably among species, and it remains unclear how such differences could arise within a group of closely related species using apparently similar habitats at the same locales. We mapped the spatial distributions of foraging shorebirds, as well as biotic (benthic invertebrates consumed by migrating shorebirds) and abiotic (sediment characteristics) environmental factors, at a key stopover site in eastern China. Five of the six sediment characteristics showed significant spatial variation with respect to distance along the shoreline or distance from the seawall in the same tidal flat. The biomasses of four of the six most abundant benthic invertebrates were concentrated in the upper or middle zones of the tidal flat. The distribution patterns of all three focal shorebird species on the tidal flat were best explained jointly by this heterogeneity of sediment characteristics and invertebrate prey. These results suggest that the loss of tidal flats along the Yellow Sea, which is typically concentrated at the upper and middle zones, may not only reduce the overall amount of staging habitat, but also disproportionately affect the most resource-rich portions for the birds. Effective conservation of shorebird staging areas along the EAAF and likely elsewhere must consider the subtle habitat heterogeneity that characterizes these tidal flats, prioritizing the protection of those portions richest in food resources, most frequently used by focal bird species, and most vulnerable to anthropogenic threats. Article impact statement: Heterogeneity of tidal flats with respect to biotic and abiotic factors must be considered in shorebird conservation planning.

Rise and fall of an avian oasis: Tracking the impacts of land use change in a key coastal wetland in the world's largest megalopolis

Tropical estuaries support wetlands with high biodiversity value and provide essential ecosystem services. Many of these systems, however, are global hotspots for urbanization, particularly in Asia, where this process has resulted in rapid conversion, fragmentation, and degradation of 80 % of the wetlands along the East Asian-Australasian Flyway (EAAF) for migratory birds. However, the impact of such landscape scale changes on migratory birds at a key stopover site along the EAAF has not been evaluated. Here, we used long-term data (> 40 years) from Deep Bay (Hong Kong), a shallow embayment in the Pearl River estuary (PRE) in south China, to investigate the impact of urbanization on (1) catchment land use and water quality, and (2) its impact on the capacity of the wetland to support populations of migratory waterbirds. Deep Bay supports the largest remnants of mangrove forests and tidal mudflats in the PRE and is an important refueling ground along the EAAF. It is also part of the Greater Bay Area (GBA, population 86 million), the world's largest megalopolis. The principal component analysis highlighted the nutrient loading and cleansing effect from seasonal flushing as characterizing variation in water quality in Deep Bay over four decades. Major shifts in water quality during the study period were accompanied by contemporaneous changes in wintering waterbirds numbers. Prior to 2003, the main drivers of water quality were organic nutrients from animal husbandry. Following large-scale reclamation and increases in impervious surface cover post-2003, primarily due to the development of the megacity of Shenzhen (population 17.7 million), the hydrodynamics of Deep Bay have changed, with knock-on effects of sedimentation, input of pollutants, and changes in the macrobenthos. The wintering waterbirds community responded to these changes both in total numbers and the relative importance of feeding guilds. Where total bird counts are positively influenced by benthic biomass, and the benthic biomass is positively correlated to the water quality that is driven by the cleansing effect of tidal flushing. These anthropogenic drivers have negatively impacted migratory birds that use Deep Bay as a refueling station. This study highlights the need for policymakers to control these drivers and limit the level to which sensitive coastlines are urbanized.

Identifying the wetlands of international importance in Beibu Gulf along the East Asian – Australasian Flyway, based on multiple citizen science datasets

The Beibu Gulf (Gulf of Tonkin, Vinh Bac Bo in Vietnamese), located midway along the East Asian-Australasian Flyway (EAAF), is a critical stopover and wintering region for migratory waterbirds. This transboundary coastal region, spanning between China and Vietnam, harbors diverse wetland habitats that provide refuge to waterbird species, including highly threatened species such as the spoon-billed sandpiper (CR) and the black-faced spoonbill (EN). However, the scarcity of comprehensive assessments regarding waterbird abundances, distribution, key wetland habitats, and regional threats hinders our understanding of its conservation significance at the flyway level. Further research is needed to address these knowledge gaps and facilitate effective conservation efforts in the Beibu Gulf. By synthesizing accessible citizen science datasets and published records from wetland sites in south China and northeast Vietnam, we concluded that at least 97 waterbird species used the Gulf’s wetlands during their annual cycle. Among surveys conducted from 2014 to 2022, 5 and 11 waterbird species were considered as first and second class protected species under the National Key Protected Wild Animal List in China; 2 species were listed as Critically Endangered on the IUCN Red List, 4 as Endangered and 2 as Vulnerable, underlying the critical importance of the Beibu Gulf for the survival of these species. Our study identified 25 sites in the Beibu Gulf that met the criteria for designation as internationally important wetlands. Alarmingly, less than a quarter (n = 5, or 20%) of these sites benefit from national or international protection. Localized threats, including aquatic resource harvesting, hunting, and aquaculture/fisheries, were widespread in the region. This study provides a crucial scientific baseline for continued waterbird monitoring, site prioritization, and the development of effective habitat management plans to conserve vital coastal wetland habitats in the Beibu Gulf in China and Vietnam.

Arriving late and lean at a stopover site is selected against in a declining migratory bird population.

Loss and/or deterioration of refuelling habitats have caused population declines in many migratory bird species but whether this results from unequal mortality among individuals varying in migration traits remains to be shown. Based on 13 years of body mass and size data of great knots (Calidris tenuirostris) at a stopover site of the Yellow Sea, combined with resightings of individuals marked at this stopover site along the East Asian-Australasian Flyway, we assessed year to year changes in annual apparent survival rates, and how apparent survival differed between migration phenotypes (i.e. migration timing and fuel stores). The measurements occurred over a period of habitat loss and/or deterioration in this flyway. We found that the annual apparent survival rates of great knots rapidly declined from 2006 to 2018, late-arriving individuals with small fuel stores exhibiting the lowest apparent survival rate. There was an advancement in mean arrival date and an increase in the mean fuel load of stopping birds over the study period. Our results suggest that late-arriving individuals with small fuel loads were selected against. Thus, habitat loss and/or deterioration at staging sites may cause changes in the composition of migratory phenotypes at the population-level.

Livelihoods and human impacts in Tan Thanh mudflat, Tien Giang Province, Vietnam

Tan Thanh mudflat in Tien Giang Province is one of the important wetlands of the Mekong Delta in Southern Vietnam. International conservation organizations have proposed this area to be an important bird and biodiversity area – IBAs because of the near location to the core of the East Asian-Australasian Flyway of migratory birds and providing feeding habitats for local shorebirds and endangered migratory species such as the Spoon-billed Sandpiper (Calidris pygmaea). To understand the threats human beings have on this proposed protected wetland, we conducted a study in August 2022 to assess the impacts of local community activities on the area. We used structured interviews with a site survey and mapping as the main methods of the study. The result showed that anthropogenic causes including agrochemical overuse, solid waste pollution, frequent disturbances from clam harvesting activities and illegal wild bird catching to protect cultivated farms, caused adverse impacts on the area. The study also revealed that the local communities have not been fully aware of the responsibility of protecting wild birds and the coastal environment. We suggested that to conserve the wetland successfully, we need to do further studies to fully understand the values of the wetland services to the wild birds and local communities and then engage relevant stakeholders to find solutions for improving public awareness about the importance of the wetland and inclusively protecting the area for sustainable development.

Projection of the potential distribution of suitable habitats for Siberian crane (Grus leucogeranus) in the middle and lower reaches of the Yangtze River basin

Introduction: The middle and lower reaches of the Yangtze River basin (hereafter MLYRB) are one of the most important wintering grounds for waterbirds along the East Asian-Australasian Flyway (EAAF). Climate change and human activities have greatly altered the habitats of waterbirds in this region.Methods: The potential distribution of suitable habitats for the Siberian crane (Grus leucogeranus) in the MLYRB was projected using Maximum Entropy Models (MaxEnt) and three Global Climate Models (GCMs). Additionally, estimations for temperature and precipitation before 2060 were made using CMIP6 multi-model and multi-scenario data.Results: 1) the MaxEnt model was highly applicable (AUC = 0.939) for analyzing the suitable habitat distribution and climatic suitability of Siberian cranes in the study area; 2) Precipitation of the driest quarter and altitude were the main factors affecting the potential suitable habitat distribution of Siberian cranes, accounting for 40% of the total contribution rate each; 3) The climatically suitable areas for the distribution of suitable habitats of Siberian cranes in the study area was mainly concentrated in parts of Poyang Lake, Dongting Lake, Taihu Lake, and the mainstream of the Yangtze River; 4) In the BCC-CSM2-MR, CanESM5, and CNRM-CM6-1 models, the suitable habitat area for Siberian cranes is expected to decrease under different SSP scenarios from 2021 to 2060 compared to 1970–2000.Discussion: The BCC-CSM2-MR model’s SSP2-4.5 scenario shows the most significant decline in the suitable habitat area for Siberian cranes, with a maximum decrease of approximately 35.7%, followed by a maximum decrease of about 26.2% and 16.4% under the CNRM-CM6-1 and CanESM5 models’ SSP2-4.5 scenario, respectively. In general, the suitable habitat areas for Siberian cranes are projected to decline, indicating the need for comprehensive evaluation and uncertainty research using more models.

Impact of coastal island restoration engineering and subsequent tourism on migratory waterbirds: a 3‐year case from Southern China

Coastal engineering poses a significant threat to the survival of migratory waterbirds worldwide. However, the mechanisms through which engineering affects waterbirds are still unclear. To gain a better understanding of this issue, we conducted a three‐year survey of waterbirds on Shanxinsha Island, which underwent restoration engineering, along the East Asian–Australasian Flyway. We compared the seasonal migratory change among different species groups through and after the island restoration engineering. We observed a total monthly maximum count of 118,506 individuals from 61 waterbird species over the span of 38 months, including eight globally threatened species and five species that exceeded 1% of the flyway population. Throughout the survey periods, the average number of total waterbirds and small shorebirds observed during the migrating season decreased by 52.7 and 48.6%, respectively. The massive loss of high‐tide roosting areas was the primary factor contributing to this decline. The combined effects of increased vegetation and deeper water levels resulted in a 38.8% reduction in exposed tidal flat area, as determined through land cover verification and fractional vegetation cover calculations. While tourism activities exhibited fewer negative consequences compared to island restoration engineering, they had a greater impact on small breeding shorebirds. Our study showed that small shorebirds were particularly susceptible to island restoration engineering, whereas large shorebirds and swimming birds were more flexible in their use of roosting or foraging sites. We suggest that the impact of future coastal engineering requires more detailed assessment and monitoring, especially for small migratory shorebirds.