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Migratory shorebirds are among the most threatened groups of birds. They rely on natural intertidal habitats outside the breeding season, but, to some extent have adjusted to using man-made habitats. Here, we assessed the importance of coastal saltpans – a type of anthropogenic wetland – for feeding in migratory shorebirds during their northward migration along the East Asian-Australasian Flyway (EAAF). We combined low tide counts on intertidal flats and nearby saltpans at the Luannan coastal wetland complex (Bohai Bay, China) with Bayesian mixing model analyses (BMMs) based on stable isotopes to evaluate the relative importance of coastal saltpans versus natural intertidal habitats as foraging grounds for migrating species. We grouped shorebird species (n = 24) according to feeding guild and body size, and found that both predictors explained the broad-scale patterns of foraging use of saltpans by shorebirds at low tide. The guild of water-surface foraging species (e.g. stilts and avocets), independently of body size, mostly fed in saltpans, and the small-medium visual (e.g. plovers) and tactile-surface (e.g. sandpipers) foraging species consumed a significant portion of their diet in this habitat. In contrast, most large tactile-surface foraging species barely foraged in saltpans at low tide. BMMs showed that shorebirds had a greater reliance on saltpans than did traditional counts of foraging birds in each habitat at low tide. Saltpan food is rich in essential fatty acids, so the contribution of saltpans to the diet of shorebirds should not be considered only in absolute values, but also in the quality of this contribution. Saltpans may therefore help conserve declining shorebirds if properly managed – for example by controlling water levels – to serve the specific feeding guilds that rely on them. While our focus is in the EAAF, the findings are relevant for other flyways and other non-tidal anthropogenic wetlands.

Artificial wetlands such as coastal saltpans have replaced a number of coastal natural habitats worldwide and may have accommodated specific waterbird populations in the East Asian–Australasian Flyway (EAAF). The role of saltpans in the EAAF as foraging grounds for shorebirds is widely recognized, although their role as breeding grounds for waterbirds is very limited and contradictory. The Nanpu saltpans in northern Bohai Bay, China, are one of the largest saltpan complexes in the world. In this study, wemonitored the nesting success (852 nests) of pied avocets ( Recurvirostra avosetta) during three breeding seasons (2015, 2016, and 2018) in the Nanpu saltpans. The nest daily survival rate (DSR) was 0.970; hence, nest survival over the 27 exposure days was 44%. The apparent nest success was 51%. Surprisingly, 55% of nests failed during the laying period. Flooding and nest abandonment were the main causes of nest failure during both the laying and incubation periods. We found a strong positive relationship between the DSR and nest age, with nests that approached hatching having a greater probability of survival than freshly started nests. We also found a strong negative relationship between the DSR and precipitation, with the highest DSR observed for nests that experienced no precipitation. The DSR decreased over the course of the 71-days nesting season and followed a linear trend. The DSR was also density dependent and decreased slightly when nests were denser. A literature review showed that nest survival in the Nanpu saltpans was average compared with that of other studies and that nest success in artificial wetlands was significantly higher than that in natural wetlands or both habitats. Nevertheless, nest success decreased with the study date, suggesting that that breeding conditions for the pied avocet are worsening with time. The loss of saltpans could negatively affect the population of avocets and other ground-nesting waterbird species; therefor

Few studies have been able to directly measure the seasonal survival rates of migratory species or determine how variable the timing of migration is within individuals and across populations over multiple years. As such, it remains unclear how likely migration is to affect the population dynamics of migratory species and how capable migrants may be of responding to changing environmental conditions within their lifetimes. To address these questions, we used three types of tracking devices to track individual black-tailed godwits from the nominate subspecies (Limosa limosa limosa) throughout their annual cycles for up to 5 consecutive years. We found that godwits exhibit considerable inter- and intra-individual variation in their migratory behavior across years. We also found that godwits had generally high survival rates during migration, although survival was reduced during northward flights across the Sahara Desert. These patterns differ from those observed in most other migratory species, suggesting that migration may only be truly dangerous when crossing geographic barriers that lack emergency stopover sites and that the levels of phenotypic flexibility exhibited by some populations may enable them to rapidly respond to changing environmental conditions.

Many shorebird populations are in decline along the East Asian-Australasian Flyway. The rapidloss of coastal wetlands in the Yellow Sea, which provide critical stop-over sites during migration,is believed to be the cause of the alarming trends. The Yalu Jiang coastal wetland, a protectedarea in the north Yellow Sea, supports the largest known migratory staging populationsof Bar-tailed Godwits Limosa lapponica (menzbieri and baueri subspecies) and Great KnotsCalidris tenuirostris. Monitoring of the macrozoobenthos food for these shorebirds from 2011to 2016 showed declines of over 99% in the densities of the bivalve Potamocorbula laevis, themajor food here for both Bar-tailed Godwits and Great Knots. The loss of the bivalve might becaused by any combination of, but not limited to: (1) change in hydrological conditions andsediment composition due to nearby port construction, (2) run-off of agrochemicals from theextensive shoreline sea cucumber farms, and (3) parasitic infection. Surprisingly, the numbersof birds using the Yalu Jiang coastal wetland remained stable during the study period, exceptfor the subspecies of Bar-tailed Godwit L. l. menzbieri, which exhibited a 91% decline in peaknumbers. The lack of an overall decline in the number of bird days in Great Knots and in thepeak numbers of L. l. baueri, also given the published simultaneous decreases in their annualsurvival, implies a lack of alternative habitats that birds could relocate to. This study highlightsthat food declines at staging sites could be an overlooked but important factor causing populationdeclines of shorebirds along the Flyway. Maintaining the quality of protected staging sitesis as important in shorebird conservation as is the safeguarding of staging sites from land claim.Meanwhile, it calls for immediate action to restore the food base for these beleaguered migrantshorebirds at Yalu Jiang coastal wetland.

In response to environmental change, species have been observed altering their migratory behaviours. Few studies, however, have been able to determine whether these alterations resulted from inherited, plastic or flexible changes. Here, we present a unique observation of a rapid population-level shift in migratory routes—over 300 km from Spain to Portugal—by continental black-tailed godwits Limosa limosa limosa. This shift did not result from adult godwits changing staging sites, as adult site use was highly consistent. Rather, the shift resulted from young godwits predominantly using Portugal over Spain. We found no differences in reproductive success or survival among individuals using either staging site, indicating that the shift resulted from developmental plasticity rather than natural selection. Our results therefore suggest that new migratory routes can develop within a generation and that young individuals may be the agents of such rapid changes.

Capsule: Most Continental Black-tailed Godwits Limosa limosa limosa using the Doñana wetlandsduring post-breeding migration appear to begin moult before they arrive and suspend moultbefore they migrate onwards to West Africa.Aims: We aim to describe the primary moult strategies and patterns in the Continental Black-tailedGodwits using the Doñana wetlands, a major passage and wintering area for waterbirds in southernSpain.Methods: Individual godwits were captured, marked and their primary moult was scored in Doñanaduring the non-breeding season (June–March) in 2011 and 2012. Data from resightings of colourmarkedgodwits and birds equipped with satellite transmitters were used to estimate stopoverduration during post-breeding migration (June–September) to determine if godwits move toWest Africa before completing their primary moult.Results: Average primary moult duration was estimated to be 84 days ± 9 se, during 29 June–21September and did not differ between sexes. Only 2% of individuals were observed withsuspended moult. We estimated stopover duration in Doñana to be 13 days ± 2 se beforemigrating to West Africa.Conclusions: Most godwits stage for about two weeks in the Doñana wetlands during southwardmigration, moult their primaries and appear to suspend moult before crossing the Sahara. Othersmay complete their primary moult in Doñana, or elsewhere in Europe and overwinter in Doñanawhere increasing numbers of godwits have been detected in recent years. A few individu

Salinization is having a major impact on wetlands and its biota worldwide. Specifically, many migratoryanimals that rely on wetlands are increasingly exposed to elevated salinity on their nonbreedinggrounds. Experimental evidence suggests that physiological challenges associated with increasingsalinity may disrupt self-maintenance processes in these species. Nonetheless, the potential role ofsalinity as a driver of ecological carry-over effects remains unstudied. Here, we investigated the extentto which the use of saline wetlands during winter – inferred from feather stable isotope values – inducesresidual effects that carry over and influence physiological traits relevant to fitness in black-tailedgodwits Limosa limosa limosa on their northward migration. Overwintering males and females weresegregated by wetland salinity in West Africa, with females mostly occupying freshwater wetlands.The use of these wetlands along a gradient of salinities was associated with differences in immuneresponsiveness to phytohaemagglutinin and sized-corrected body mass in godwits staging in southernEurope during northward migration – 3,000 km from the nonbreeding grounds – but in males only.These findings provide a window onto the processes by which wetland salinity can induce carry-overeffects and can help predict how migratory species should respond to future climate-induced increasesin salinity.

The Numeniini is a tribe of 13 wader species (Scolopacidae, Charadriiformes) of which seven are Near Threatened or globally threatened, including two Critically Endangered. To help inform conservation management and policy responses, we present the results of an expert assessment of the threats that members of this taxonomic group face across migratory flyways. Most threats are increasing in intensity, particularly in non-breeding areas, where habitat loss resulting from residential and commercial development, aquaculture, mining, transport, disturbance, problematic invasive species, pollution and climate change were regarded as having the greatest detrimental impact. Fewer threats (mining, disturbance, problematic native species and climate change) were identified as widely affecting breeding areas. Numeniini populations face the greatest number of non-breeding threats in the East Asian-Australasian Flyway, especially those associated with coastal reclamation; related threats were also identified across the Central and Atlantic Americas, and East Atlantic flyways. Threats on the breeding grounds were greatest in Central and Atlantic Americas, East Atlantic and West Asian flyways. Three priority actions were associated with monitoring and research: to monitor breeding population trends (which for species breeding in remote areas may best be achieved through surveys at key non-breeding sites), to deploy tracking technologies to identify migratory connectivity, and to monitor land-cover change across breeding and non-breeding areas. Two priority actions were focused on conservation and policy responses: to identify and effectively protect key non-breeding sites across all flyways (particularly in the East Asian- Australasian Flyway), and to implement successful conservation interventions at a sufficient scale across human-dominated landscapes for species’ recovery to be achieved. If implemented urgently, these measures in combination have the potential to alter the cu

Over the past 50 years, the population of Continental Black-tailed GodwitsLimosa limosa limosa breeding of the East Atlantic Flyway has been in steepdecline. This decline has previously been documented in trend analyses and sixNetherlands-wide count-based population estimates, the last of which wascompleted in 1999. We provide an updated population size estimate anddescribe inter-annual fluctuations in the population between 2007 and 2015. Togenerate these estimates, we integrated a mark-recapture survival analysis withestimates of the densities of colour-marked individuals at migratory staging siteswith known proportions of Continental and Icelandic L. l. islandica Black-tailedGodwits within a Bayesian framework. The use of these analytical techniquesmeans that, in contrast with earlier efforts, our estimates are accompanied withconfidence intervals, allowing us to estimate the population size with knownprecision. Using additional information on the breeding destination of 43 godwitsequipped with satellite transmitters at Iberian staging areas, we found that 87%(75–95% 95% CI) of the nominate subspecies in the East Atlantic Flyway breedin The Netherlands. We estimated that the number of breeding pairs in TheNetherlands has declined from 47,000 (38,000–56,000) pairs in 2007 to 33,000(26,000–41,000) in 2015. Despite a temporary increase in 2010 and 2011, thepopulation declined by an average of 3.7% per year over the entire period from2007–2015, and by 6.3% from 2011–2015. We conclude that investing in anintensive demographic programme at a regional scale, when combined withtargeted resightings of marked individuals elsewhere, can yield population estimatesat the flyway scale.

Migratory shorebirds inhabit environments that may yield contrasting salinity-temperature regimes—with widely varying osmoregulatory demands, even within a given species—and the question is: by which physiological means and at which organisational level do they show adjustments with respect to these demands? Red knots Calidris canutus winter in coastal areas over a range of latitudes. The nominal subspecies winters in salty areas in the tropics, whereas the subspecies Calidris canutus islandica winters in north-temperate regions of comparatively lower salinities and temperatures. In this study, both subspecies of red knot were acclimated to different salinity (28/40 ‰)–temperature (5/35 °C) combinations for 2-week periods. We then measured food/salt intakes, basal metabolic rate (BMR), body mass and temperature, fat and salt gland scores, gizzard mass, heat-shock proteins, heterophils/lymphocytes (H/L) ratio and plasma Na+ to assess the responses of each taxon to osmoregulatory challenges. High salinity (HS)-warm-acclimated birds reduced food/salt intake, BMR, body mass, fat score and gizzard mass, showing that salt/heat loads constrained energy acquisition rates. Higher salt gland scores in saltier treatments indicated that its size was adjusted to higher osmoregulatory demands. Elevated plasma Na+ and H/L ratio in high-salinity-warm-acclimated birds indicated that salt/heat loads might have a direct effect on the water-salt balance and stress responses of red knots. Subspecies had little or no effect on most measured parameters, suggesting that most adjustments reflect phenotypic flexibility rather than subspecific adaptations. Our results demonstrate how salinity and temperature affect various phenotypic traits in a migrant shorebird, highlighting the importance of considering these factors jointly when evaluating the environmental tolerances of air-breathing marine taxa

Natural and anthropogenic Iberian wetlands in southern Europe are well known for supporting large numbers of migratory Palaearctic waterbirds each winter. However, information on the geographical origin of dabbling ducks overwintering in these wetlands is scarce and mostly limited to data from ringing recoveries. Here, we used intrinsic isotopic markers to determine the geographical origin of male and female Northern Pintails Anas acuta and Eurasian Teal Anas crecca in Extremadura, inland Iberia, a key site for overwintering dabbling ducks. Additionally, we fitted six Northern Pintails with GPS-GSM tags to complement the data derived from stable isotope analysis. Most (> 70%) first calendar-year Northern Pintails were assigned to regions above 55°N, flying 2600–5600 km from their main natal regions to Extremadura. Mean values of d2Hf varied significantly between male and female Northern Pintails, suggesting that the sexes had different geographical origins. Data from tagged adult Northern Pintails supported the isotopic data, one male flying more than 5000 km to the coast of the Pechora Sea (Russia). Most (> 70%) first calendar-year Eurasian Teal were assigned to the region between 48° and 60°N, travelling 1500–4500 km to arrive in Extremadura. Male and female Eurasian Teal showed marginal differences in mean values of d2Hf. In migratory dabbling ducks, pairing typically occurs on the wintering grounds, and ducks in their first winter can breed the following spring. For Northern Pintails, pair formation in Extremadura could occur between individuals with different geographical origins, which could contribute to the genetic variability of their offspring

1. Extreme weather events have the potential to alter both short- and long-term population dynamics as well as community- and ecosystem-level function. Such events are rare and stochastic,making it difficult to fully document how organisms respond to them and predict therepercussions of similar events in the future.2. To improve our understanding of the mechanisms by which short-term events can incur long-term consequences, we documented the behavioural responses and fitness consequences for a long-distance migratory bird, the continental black-tailed godwit Limosa limosa limosa, resulting from a spring snowstorm and three-week period of record low temperatures.3. The event caused measurable responses at three spatial scales – continental, regional and local – including migratory delays (+19 days), reverse migrations (>90 km), elevated metaboliccosts (+8?8% maintenance metabolic rate) and increased foraging rates (+37%).4. There were few long-term fitness consequences, however, and subsequent breeding seasons instead witnessed high levels of reproductive success and little evidence of carry-over effects.5. This suggests that populations with continued access to food, behavioural flexibility and time to dissipate the costs of the event can likely withstand the consequences of an extreme weather event. For populations constrained in one of these respects, though, extreme events may entail extreme ecological consequences.

Waterbirds can reallocate a considerable amount of nutrients within agricultural fields and between agriculture sites and wetlands. However their effects on biogeochemical cycles have rarely been quantified. We estimated bird numbers, diet (from stable isotope analysis), food supply, and the food consumption on rice fields by overwintering waterbirds in one of the most important areas for rice production in southwestern Europe and a key area for various migrating and resident waterbird species. Herein, we modelled the nutrient (N and P) recycling in rice fields, and their transport to reservoirs. The energy consumption by waterbirds (96,605 ± 18,311 individuals) on rice fields during winter averaged at 89.9 ± 39.0 kJ·m- 2, with its majority (89.9%) belonging to foraging on rice seeds. Thus, the birds removed about 26% of rice seeds leftover after harvest (estimated in 932.5 ± 504.7 seeds·m- 2 in early winter) wherein common cranes and dabbling ducks (four species) were the most important consumers. Waterbirds foraging and roosting in the rice fields recycled more than 24.1 (1.0 kg·ha- 1) of N and an additional 5.0 tons (0.2 kg·ha- 1) of P in the Extremadura's rice fields during winter. Additionally, we estimated that 2.3 tons of N and 550 kg of P were removed from rice fields and transported to reservoirs. The seasonal foraging of wildlife should result in a direct benefit for rice farmers by improving nutrient recycling through defecation by waterbirds with respect to artificial fertilisation. Additionally, rice fields located in the cranes' core wintering areas can provide sufficient food supply to induce habitat shift from their traditional wintering habitat in ‘dehesas’ to rice fields, which causes indirect socioeconomic benefit through reduced acorn consumption by cranes. Our modelling approach may thus be especially helpful for management decisions regarding rice agroecosystems in areas which are also important for the conservation of migratory waterbirds.

Resolving the migratory connectivity (identifying non-breeding grounds) of migrating bird populations that are morphologically similar is crucial for an understanding of their population dynamics and ultimately their conservation. Such is the case in Black-tailed Godwits Limosa limosa, where the Iceland-breeding subspecies islandica shows overlap during the non-breeding season with the continental-Europe-breeding limosa. On the basis of variation in the control region of mitochondrial DNA, it was already shown that there is a cleat geographic structure in their phylogeography and a clear discrimination between the haplotypes of the two subspecies. We can thus assign subspecies of non-breeding individuals on the basis of a molecular assay. Here we validated this approach using samples of 113 birds with known breeding origin, and on the basis of haplotype variation, all birds were properly assigned to each subspecies. We then tested for overlap during non-breeding season using a sample of 278 birds from an Iberian wintering and staging area, the inland rice fields in southwest Iberia (Extremadura, Spain). We showed that even in this inland area, 6.5 % of the birds belonged to islandica subspecies, thus demonstrating the usefulness of genetic markers as an alternative or supplementary method to the most common approach, individual colour-ringing.