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Until recently, Limosa limosa melanuroides was thought to be the only subspecies of Black-tailed Godwit in the East Asian–Australasian Flyway. For this reason, all previous occurrences and counts ofBlack-tailed Godwits in the flyway have been assigned to melanuroides. However, a larger-bodied subspecies, bohaii , has recently been discovered in the flyway. As a result, the occurrence of Black-tailed Godwits in the flyway needs to be reconsidered such that the specific distribution of each subspecies becomes known. To this end, we developed a simple discriminant function to assign individuals to subspecies based on their bill and wing length. Cross-validation with individuals known to be bohaii or melanuroides, based on molecular analysis, showed the developed function to be 97.7% accurate. When applied to measurements of godwits captured at 22 sites across 9countries in East–Southeast Asia and Australia, we found that bohaii and melanuroides occurred at most sites and overlapped in their distribution from Kamchatka to Australia. We examined photos from all along the flyway to verify this surprising result, confirming that both subspecies co-occur in most locations. Based on these results, we hypothesise that bohaii and melanuroides from the west of their breeding ranges mostly migrate over Chinese mainland. Birds of both subspecies from the east of their ranges are expected to migrate along the Pacific Ocean. We encourage ringing groups in East–Southeast Asia and Australia to use this simple method to keep adding knowledge about Black-tailed Godwits in the East Asian–Australasian Flyway.

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.

Long-distance migratory species often include multiple breeding populations, with distinct migration routes, wintering areas and annual-cycle timing. Detailed knowledge on population structure and migratory connectivity provides the basis for studies on the evolution of migration strategies and for species conservation. Currently, five subspecies of Bar-tailed Godwits Limosa lapponica have been described. However, with two apparently separate breeding and winteringareas, the taxonomic status of the subspecies L. l. taymyrensis remains unclear. Here we compare taymyrensis Bar-tailed Godwits wintering in the Middle East and West Africa, respectively, with respect to migration behaviour, breeding area, morphology and population genetic differentation in mitochondrial DNA. By tracking 52 individuals from wintering and staging areas over multiple years, we show that Bar-tailed Godwits wintering in the Middle East bred on the northern West-Siberian Plain (n = 19), while birds from West Africa bred further east, mostly on the Taimyr Peninsula (n = 12). The two groups differed significantly in body size and shape, and also in the timing of both northward and southward migrations. However, they were not genetically differentiated, indicating that the phenotypic (i.e. geographical, morphological and phenological) differences arose either veryrecently or without current reproductive isolation. We conclude that the taymyrensis taxon consists of two distinct populations with mostly non-overlapping flyways, which warrant treatment as separate taxonomicunits. We propose to distinguish a more narrowly defined taymyrensis subspecies (i.e. the Bar-tailed Godwits wintering in West Africa and breeding on Taimyr), from a new subspecies (i.e. the birds wintering in the Middle East and breeding on the northern West-Siberian Plain).

Present-day ecology and population structure are the legacies of past climate and habitat perturbations, and this is particularly true forspecies that are widely distributed at high latitudes. The red knot, Calidris canutus, is an arctic-breeding, long-distance migratory shorebird with six recognized subspecies defined by differences in morphology, migration behavior, and annual cycle phenology, in a global distribution thought to have arisen just since the last glacial maximum (LGM). We used nextRAD sequencing of 10,881 single-nucleotide polymorphisms (SNPs) to assess the neutral genetic structure and phylogeographic history of 172 red knots representing all known global breeding populations. Using population genetics approaches, including model-based scenario-testing in an approximate Bayesian computation (ABC) framework, we infer that red knots derive from two main lineages that diverged ca. 34,000 years ago, and thus most probably persisted at the LGM in both Palearctic and Nearctic refugia, followed by at least two instances of secondary contact andadmixture. Within two Beringian subspecies (C. c. roselaari and rogersi), we detected previously unknown genetic structure among sub-populations sharing a migratory flyway, reflecting additional complexity in the phylogeographic history of the region. Conversely, we found very weak genetic differentiation between two Nearctic populations (rufa and islandica) with clearly divergent migratory phenotypes and little or no apparent contact throughout the annual cycle. Together, these results suggest that relative gene flow among migratory populations reflects a complex interplay of historical, geographical, and ecological factors.

1. Identifying where and when population “bottlenecks” occur is critical to the conservation of migratory species, many of which are declining precipitously worldwide. Especially challenging is the evaluation of changes to staging sites. These sites are indispensable links in the migratory cycle but are typically used only briefly. 2. We devised a field-based approach to assess the quality and carrying capacity of a critical staging site in Nanpu, China, for the declining, migratory Red Knot (Calidris canutus rogersi & C. c. piersmai) during northward migration. The Nanpu tidal flat supports 50,000-100,000 Red Knotsannually, and while there, the knots feed almost exclusively on the bivalve Potamocorbula laevis. We simultaneously monitored changes in the abundance of Red Knots and bivalves across the entire staging site in spring 2018. 3. After taking into account potential competition with other shorebird species, we estimated that the Nanpu tidal flat was capable of supporting approximately 1.46-1.70 times the current observed level of usage of the site by Red Knots, and therefore is operating below, but close, to carrying capacity with respect to food resources for Red Knots. This result suggests that any further development of this site could harm the EAAF Red Knot population. 4. Synthesis and applications: Quantitative monitoring and evaluation of habitat quality of staging sites are essential to successfully conserve declining migratory species. In particular, researchers and conservation practitioners should incorporate both population size and staging duration in order to more accurately assess the importance of different sites and to quantify how changes in staging habitat quality may translate into changes in migrant population sizes at both local and global scales.

Satellite and GPS tracking technology continues to reveal new migration patterns of birds which enables comparative studies of migration strategies and distributional information useful in conservation. Bar-tailed godwitsin the East Asian–Australasian Flyway Limosa lapponica baueri and L. l. menzbieri are known for their long non-stop flights, howeverthese populations are in steep decline. A third subspecies in this flyway, L. l. anadyrensis, breeds in the Anadyr River basin, Chukotka,Russia, and is morphologically distinct from menzbieri and baueri based on comparison of museum specimens collected from breeding areas. However, the non-breeding distribution, migration route and population size of anadyrensis are entirely unknown. Among 24 female bar-tailed godwits tracked in 2015–2018 from northwest Australia, the main non-breeding area for menzbieri, two birds migrated further eastthan the rest to breed in the Anadyr River basin, i.e. they belonged to the anadyrensis subspecies. During pre-breeding migration, all birds staged in the Yellow Sea and then flew to the breeding grounds in the eastern Russian Arctic. After breeding, these two birds migrated southwestward to stage in Russia on the Kamchatka Peninsula and on Sakhalin Island en route to the Yellow Sea. This contrasts with the other 22tracked godwits that followed the previously described route of menzbieri, i.e. they all migrated northwards to stage in the New Siberian Islands before turning south towards the Yellow Sea, and onwards to northwest Australia. Since the Kamchatka Peninsula was not used by any of the tracked menzbieri birds, the 4500 godwits counted in theKhairusova–Belogolovaya estuary in western Kamchatka may well be anadyrensis. Comparing migration patterns across the three bar-tailed godwits subspecies, the migration strategy of anadyrensis lies between that of menzbieri and baueri. Futur

The fast economic development of the People’s Republic of China has created an increasing demand for usable land, resulting in large-scale land reclamations along the coastal zone. One of these regions is Tongzhou Bay (Jiangsu coast), a region characterized by large intertidal mudflats and deep tidal channels with potential for the development of agri-aquaculture and the construction of a deep-sea port. However, these intertidal mudflats also provide vital ecosystem services and support many wildlife species, including several endangered migratory shorebirds within the East Asian–Australasian Flyway. With increasing realization of the importance of maintaining such ecological values, a more integrated coastal development strategy is needed. This study aims to develop a sustainable integrated design for the Tongzhou Bay port, following a “Building with Nature” approach. We use a morphodynamic model to compute habitat suitability for two shorebird species (Great Knot Calidris tenuirostris and Bar-tailed Godwit Limosa lapponica). Several port configurations were developed on the basis of three design criteria: (1) create area for future port development, whilst (2) preserving existing high-value ecotopes for shorebirds and (3) enhance the natural accretion rate of such ecotopes. Simulation results showed a clear difference in siltation patterns, preservation and enhancement of preferred ecotopes. This work therefore demonstrates the potential and importance of morphological and habitat suitability modelling when designing large-scale reclamations and port constructions, especially in dynamic areas such as Tongzhou Bay.

Capsule: Black-tailed Godwits Limosa limosashow sexual size dimorphism and size differences between the subspecies. The shape varies slightly between the subspecies, but not between the sexes.Aims: To investigate whether and how the three subspecies of Black-tailed Godwits, and the sexes of these subspecies, differ in size and shape.Methods: We collected body dimensions (lengths of the bill, total head, tarsus, tarsus-toe and wing) of adult Black-tailed Godwits from three locations (Iceland, the Netherlands and northwest Australia) corresponding to the breeding or wintering grounds of three known subspecies (islandica, limosa and melanuroides, respectively). Determining sex by molecular assays, we computed degrees of sexual size dimorphism. Using principal component analysis (PCA), we compared differences in size and shape among the different subspecies.Results: The limosa subspecies was the largest and also showed the most significant sexual size dimorphism. Sexual size dimorphism was smallest for wing length and largest for bill length. The first two axes of the PCA that included all subspecies of both sexes explained 94% of the total variation. Most body dimensions were highly correlated with each other, but wing length varied independently of the other dimensions. Males and females differed only in size (the first axis). However, one of the two small subspecies, islandica, also differed in shape (the second axis) from limosa and melanuroides.Conclusions: In all three subspecies of Black-tailed Godwits, females are larger than males. The fact that subspecies differed in the degree of size dimorphism and slightly in shape hints at sex-related differences in the ecological selection pressures between the different flyways.

1. Satellite‐based technologies that track individual animal movements enable the mapping of their spatial and temporal patterns of occurrence. This is particularly useful in poorly studied or remote regions where there is a need for the rapid gathering of relevant ecological knowledge to inform management actions. One such region is East Asia, where many intertidal habitats are being degraded at unprecedented rates and shorebird populations relying on these habitats show rapid declines.2. We examine the utility of satellite tracking to accelerate the identification of coastal sites of conservation importance in the East Asian–Australasian Flyway. In 2015–2017, we used solar‐powered satellite transmitters to track the migration of 32 great knots (Calidris tenuirostris), an “Endangered” shorebird species widely distributed in the Flyway and fully dependent on intertidal habitats for foraging during the non‐breeding season. 3. From the great knot tracks, a total of 92 stopping sites along the Flyway were identified. Surprisingly, 63% of these sites were not known as important shorebird sites before our study; in fact, every one of the tracked individuals used sites that were previously unrecognized.4. Site knowledge from on‐ground studies in the Flyway is most complete for the Yellow Sea and generally lacking for Southeast Asia, Southern China and Eastern Russia.5. Synthesis and applications. Satellite tracking highlighted coastal habitats that are potentially important for shorebirds but lack ecological information and conservation recognition, such as those in Southern China and Southeast Asia. At the same time, the distributional data of tracked individuals can direct on‐ground surveys at the lesser known sites to collect information on bird numbers and habitat characteristics. To recognize and subsequently protect valuable coastal habitats, filling knowledge gaps by integrating bird tracking with ground‐based methods should be prioritized.

Prompted by the realization that parts of the coast of southern Jiangsu Province, China, are under threat of reclamation, we here summarize evidence that loss of intertidal habitats around the Yellow Sea and at other parts along the Chinese and Korean coasts has already led to severe population declines of migratory shorebirds, including multiple endangered species. All the evidence currently at hand suggest that the plans to reclaim (develop) additional intertidal habitat in this region poses a substantial threat to the remaining shorebird populations. We recommend that new Environmental Impact Assessments are warranted before further reductions in the extent of mudflats take place.

The departure of migratory birds from their non-breeding grounds is thought to be driven by the phenologyof their breeding destination. In north-west Australia, two plumage morphs of Red Knot (Calidris canutus) prepare for a5500-km journey to Yellow Sea staging areas. These morphs are recognised as the subspecies C. c. piersmai and C. c. rogersi,which breed at different latitudes and have different seasonalities. From February to May 2011, we observed the migratorypreparation of individually marked birds of known age, sex and type. This enabled a comparison of fuelling rates and prealternatemoult among these classes. First-year birds did not prepare for migration. Second-year birds accumulatedsmaller fuel stores and reached lower plumage scores than adults. Adults of both types reached their highest abdominalprofile scores by the end of April when they were last observed in Roebuck Bay. This lack of difference between types inthe timing of fuelling and departure is surprising. Based on the differences in staging and breeding phenology, C. c. rogersiis expected to leave north-west Australia 2–4 weeks before C. c. piersmai. Assuming that types and subspecies are equivalent,our findings in combination with other research on Red Knots in the East Asian–Australasian Flyway suggest that it takesmore than breeding origin alone to explain annual cycles in migratory birds. Concurrent migratory schedules imply that,during northward staging in the Yellow Sea, there is strong variation in fuelling rates between and within subspeciesdepending on non-breeding origin. The ongoing loss of staging habitat may therefore have differential effects on Red Knotsin the East Asian–Australasian Flyway.

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 t

In general, Arctic-breeding waders leave non-breeding grounds in Australasia from March (New Zealand) to mid-April (Northwest Australia). Here we provide evidence from radio-tracking and visual observations that many red knots Calidris canutus do not leave Roebuck Bay, Northwest Australia, until early or mid-May. Late-departing red knots probably belong to the subspecies piersmai, which breeds on the New Siberian Islands, 10,400 km from Northwest Australia. Based on comparisons of temperatures on the breeding grounds of different knot subspecies, we predict that piersmai knots would not arrive on the breeding grounds until early June, leaving at most 3–4 weeks refuelling in Asia. Using a model of fuelling capacity in relation to prey quality and gizzard mass, we show that these knots must fuel very differently in Australia and Asia. In Australia, knots have seemingly suboptimal gizzard sizes and deposit fuel slowly. In the Yellow Sea, birds could only fuel up within the available time if they either enlarged their gizzards substantially or encountered prey qualities much higher than in Australia, for which we provide quantitative predictions., In general, Arctic-breeding waders leave non-breeding grounds in Australasia from March (New Zealand) to mid-April (Northwest Australia). Here we provide evidence from radio-tracking and visual observations that many red knots Calidris canutus do not leave Roebuck Bay, Northwest Australia, until early or mid-May. Late-departing red knots probably belong to the subspecies piersmai, which breeds on the New Siberian Islands, 10,400 km from Northwest Australia. Based on comparisons of temperatures on the breeding grounds of different knot subspecies, we predict that piersmai knots would not arrive on the breeding grounds until early June, leaving at most 3–4 weeks refuelling in Asia. Using a model of fuelling capacity in relation to prey quality and gizzard mass, we show that these knots must fuel very differently in Australia and Asia. In Australia, knots have seemingly suboptimal gizzard sizes and deposit fuel slowly. In the Yellow Sea, birds could only fuel up within the available time if they either enlarged their gizzards substantially or encountered prey qualities much higher than in Australia, for which we provide quantitative predictions.