Many migratory birds exhibit interannual consistency in migration schedules,routes and stopover sites.Detecting the interannual consistency in spatiotemporal characteristics helps understand the maintenance of migration and enables the implementation of targeted conservation measures.We tracked the migration of Whimbrel(Numenius phaeopus)in the East Asian-Australasian Flyway and collected spatiotemporal data from individuals that were tracked for at least two years.Wilcoxon non-parametric tests were used to compare the interannual variations in the dates of departure from and arrival at breeding/nonbreeding sites,and the inter-annual variation in the longitudes when the same individual across the same latitudes.Whimbrels exhibited a high degree of consistency in the use of breeding,nonbreeding,and stopover sites between years.The variation of arrival dates at nonbreeding sites was significantly larger than that of the departure dates from nonbreeding and breeding sites.Repeatedly used stopover sites by the same individuals in multiple years were concentrated in the Yellow Sea coast during northward migration,but were more widespread during southward migration.The stopover duration at repeatedly used sites was significantly longer than that at sites used only once.When flying across the Yellow Sea,Whimbrels breeding in Sakha(Yakutia)exhibited the highest consistency in migration routes in both autumn and spring.Moreover,the consistency in migration routes of Yakutia breeding birds was generally higher than that of birds breeding in Chukotka.Our results suggest that the northward migration schedule of the Whimbrels is mainly controlled by endogenous factors,while the southward migration schedule is less affected by endogenous factors.The repeated use of stopover sites in the Yellow Sea coast suggests this region is important for the migration of Whimbrel,and thus has high conservation value.

Reproduction investment is a prominent trade-off in life-history theory and is subject to strong selection pressure.The avian eggshell,as a crucial barrier between the bird embryo and the surrounding environment,undergoes optimization under different environmental selection regimes to ensure the successful development of embryos,which can be linked to local adaptation.Therefore,understanding the variation in eggshell microstructure and composition in wild bird populations living in contrasting ambient environments is of great significance.In this study,we utilized electron microscope ultrastructure measurement and elemental analyses to measure and compare the microstructure and element composition of eggshells from three wild plover populations(Charadrius alexandrinus and C.dealbatus)residing in heterogeneous habitats across varied climatic zones.These populations include the high-altitude Qinghai Lake population,the temperate coastal Tangshan population,and the tropical coastal Zhanjiang population.Our findings revealed that the palisade layer was thinner in the Qinghai Lake population compared to its lowland populations.This difference might be attributed to hypoxia which facilitates the hatching process by allowing chicks to easily break through their shells.Additionally,the variations in the elemental composition of the eggshells among populations well reflected the distribution of element content in different geographical regions.The Qinghai Lake population displayed low zinc and low manganese levels but high calcium levels,while the Zhanjiang population exhibited high zinc,high iron,high manganese,and high phosphorus levels.Furthermore,these variations in elemental composition could also account for the observed microstructural differences among populations.Collectively,we propose that the dissimilarities in eggshell microstructure and elemental composition among populations could be attributed to adaptations to different environmental conditions.Our findings lay the groundwork for future research to explore the mechanisms behind the variations in eggshell characteristics among wild bird populations,and contribute to a broader un-derstanding of biodiversity mechanisms.

China's coastal wetlands provide breeding,migration stopover,and wintering habitats for about 230 waterbird species,which is more than a quarter of all waterbirds in the world.Large-scale and high intensity human ac-tivities have resulted in serious loss and degradation of coastal wetlands over the past half century,causing population declines in many waterbirds.Through a literature review and expert surveys,this article reviews conservation measures taken in recent decades to protect waterbirds in China's coastal wetlands and provides recommendations for future conservation action from three aspects:policy and administration,habitat conser-vation and management,and multiparty participation.Over the past decades,many conservation legislation,regulations and action plans at the national level and more site-specific measures and interventions have been implemented,with notable improvement in the effectiveness in policy making and multi-stakeholder participa-tion.Accordingly,some threats to waterbirds have been mitigated and many key sites for waterbirds have been designated as strictly protected nature reserves.However,some critical issues still remain,mostly related to habitat conservation and management,such as coastal wetland restoration,control of invasive Spartina alterni-flora,control of environmental pollution,and improvement of artificial habitat quality.We highlight that pro-tecting natural tidal wetlands and improving habitat quality are critical for the conservation of coastal waterbirds,especially those highly dependent on the intertidal wetlands.China has demonstrated strong commitment to ecological conservation and restoration for the future,in terms of both funding and policies for biodiversity and wetland ecosystems.It is important that this commitment to conserve coastal waterbirds is supported continu-ously by science-and evidence-based decisions and actions.

Background:Departure decisions and behaviors of migratory birds at stopover sites are expected to maximize fitness by trade-offs among avoiding predators,optimizing refueling (energy) capacity,and matching other life-history events.We predict that species with different body sizes and migratory destinations will exhibit different behaviors when departing from the same stopover site.We also predict that with strong time constraint at the final pre-breeding stopover site,departure decisions may be less sensitive to exogenous factors,such as wind condition,compared to other stopover or nonbreeding sites.Methods:We recorded migratory departures of four shorebird species,i.e.Eurasian Curlew (Numenius arquata),Bar-tailed Godwit (Limosd lapponica),Great Knot (Calidris tenuirostris),and Grey Plover (Pluvialis squatarola),at Yalujiang Estuary Wetlands in China,a final pre-breeding stopover site in the northern Yellow Sea,from 2011 to 2014.We compared flock sizes,departure time and departure directions between species,and investigated the effects of tide and weather conditions (rain and ground wind speed and direction) on the departure decision of shorebirds.Results:We found that larger species departed in smaller flocks and were more variable in daily departure time.Departure trajectory of all four species appeared to be influenced by coastal topography.With the east-west coastline and intertidal mudflat on the south,birds exhibited westward or eastward deflection from the shortest migratory routes.Bar-tailed Godwit was the only species that deviated to the southeast and did not climb over the land.Birds avoided departure during precipitation,while their departure was not related to ground wind benefit or tidal condition.Conclusions:Body size among species,which influences their vulnerability to predators,might be important in shaping shorebird departure strategies.Diverse departure directions could be the result of different wind use tactics in climbing stage.Narrow optimal time window of breeding might lead to reduced flexibility in departure date at a final pre-breeding site.Both endogenous and exogenous are important in shaping departure behaviors and decisions.

Background: Roost-site quality can significantly affect the individual fitness of shorebirds, but roost sites remain poorly described for many threatened species on the East Asian–Australasian Flyway. We studied roost-site selection of the globally endangered Spotted Greenshank (Tringa guttifer) in the Inner Gulf of Thailand, an area which supports approximately 24% of their global wintering population, during two non-breeding seasons (October 2014–May 2015 and December 2015–February 2016). Methods: We measured nine variables associated with roost site characteristics including water depth, indicators of disturbance/predation risk, and associations with other shorebird species. We predicted that roost ponds with shallow water in proximity to foraging sites would receive higher usage than those further away. Results: A total of 94 sites were measured of which 46 were used for roosts with 23 used repeatedly. All used sites were human-modified ponds, of which 44 were used for salt farming and two used for aquaculture. Roosts were on average 1.10 ± 0.78 (SE) km from foraging sites and 5.8 ± 2.4 cm deep. The most supported model indicated that roost sites were negatively associated with distance to foraging sites and positively associated with the presence of Grey Plover (Pluvialis squatarola) and water depth. Conclusions: Traditional saltpans and other artificial wetlands near (＜ 1 km) mudflats serve as the primary high-tide roost habitat in the Inner Gulf of Thailand for this Spotted Greenshank population and perhaps seven other globally threatened or near-threatened species. Critically, all observed roost sites are on private land with no formal protection and thus will require creative public–private partnerships to manage sustainably.

Background:Restoration projects have been implemented worldwide to mitigate the adverse effects of the loss and degradation of wetland habitats. Much research has been carried out on the impacts on birds of wetland restoration and management projects in China. Studies have mainly investigated central or coastal wetlands, while inland wet-lands in remote areas have been much less studied. We focused on examining the response of wild birds to wetland restoration in Dianchi Lake, south-west China. Methods: The line transect method was performed at 26 sampling plots. Three of these were in the city, and to acquire all wild bird data 23 plots were located every 2-8 km along the shore of Dianchi Lake, between Decem-ber 2011 and November 2013. We collected all related bird records by searching the available literature, articles, newspapers and records of birdwatchers to compare species variation before and after implementation of wetland restoration. To measure the relationships between waterbird assemblages and habitat structures, we used canonical correspondence analysis (CCA) to pair the main matrix of bird assemblages with a second matrix of habitat variables. Results: We recorded 182 bird species belonging to 51 families and 17 orders. Of the species, 42 were new records for Kunming City and 20 were new records for Yunnan Province. Ten waterbird species were found to have disap-peared from the shore of Dianchi Lake. CCA results indicated that waterbirds could be divided into four categories based on their habitat preference: synanthropic (wintering gulls), special habitat (shorebirds), semi-natural (wintering coots and ducks) and disturbance-tolerant (resident) species. Conclusions: Our study is the first to consider the entire wild bird community throughout the year and discuss the species variation before and after wetland restoration projects launched for Dianchi Lake. Distinct habitat require-ments of different waterbird groups were detected in our study, suggesting different types of restoration and man-agement should be implemented.

Background:Anthropogenic disturbance can negatively affect an animal’s energy budget by evoking movement responses. Existing research focuses mainly on immediate displacement as a disturbance effect, since this can be eas-ily observed in the field. However, effects on movement over longer timescales are poorly examined and it is largely unknown if and to what extent they reflect immediate responses. Longer-term responses could for example be larger than immediate responses if birds, after disturbance, return to the original location and thereby travel twice the immediate disturbed distance. Methods: We combined GPS tracking data with observational data to quantify the effects of anthropogenic (air force and walkers) and non-anthropogenic disturbances on distances travelled by roosting Eurasian Oystercatchers (Hae-matopus ostralegus) during the non-breeding season. We compared immediate displacement after a disturbance with distance travelled during the entire high tide period (longer-term response), while accounting for environmental fac-tors. Additionally, we calculated energy expenditure due to disturbance based on observed disturbance frequencies. Results: Disturbance resulted in an immediate displacement response of ～ 200 m (median). Air force disturbances tended to yield larger immediate responses than walker and, especially, than non-anthropogenic disturbances. Longer-term responses and immediate responses were approximately similar, suggesting that, over longer timescales, spatial disturbance effects in the study area remain confined to immediate effects. However, disturbances were infrequent (0.17 disturbances per bird per hour) and most disturbances were of natural origin (62%). Consequently, anthropogenic disturbance of roosting oystercatchers in the study area on average costs 0.08% of the daily energy expenditure. Conclusions: Our results suggest that immediate spatial responses to disturbance can be a useful proxy for spatial responses over longer timescales. Over the non-exhaustive range of conditions investigated, energetic consequences of spatial disturbance responses for an oystercatcher in the study area are marginal due to low disturbance levels.

Background: Land use and development alter mudflat and wetland habitat availability, although mudflats and wetlands provide important stopover habitats for shorebirds during the spring and autumn migrations and support communities of ducks and geese during the winter months in the Republic of Korea. This study investigated land use changes around Sihwa Lake (Republic of Korea) and evaluated the effect of these changes on waterbird community characteristics. Methods: We conducted a land-use-change analysis at the medium-resolution level using land cover maps for 2001, 2007, 2009, and 2014. Also, a tidal stream survey was conducted in Sihwa Lake and the surrounding reclaimed mudflats every season for 10 years (2003–2012) to identify the seasonal and interannual variations in waterbird spe-cies composition. To determine the total annual waterbird species and population counts, species diversity index, and interspecies variations, a TRIM (trends and indices for monitoring data) analysis was used. Results: Wetland area decreased more than 10％ while agricultural land, barren land, and grassland area increased more than 10％ due to continuous reclamation activities around Sihwa Lake. Barren land later turned into agricultural land or other land use. Sixty-three species and 566,623 individuals were recorded. The number of species, population size, and species diversity index by year and by species showed decreasing trends that were more marked in spring and summer. Furthermore, seasonal and annual variations in waterbird species composition showed decreasing trends in dabbling ducks, herons, grebes, and shorebirds but diving ducks displayed increasing trends. In particular, shorebirds were reduced to a greater extent than other waterbird species because of the reduction and simplification of the intertidal zone, and shallow waters caused by reclamation and road construction. Conclusions: Increased development and construction around Sihwa Lake has altered migratory shorebird popula-tions with a general decline in species diversity and population size. The greatest decline was observed in wading birds, while diving duck populations showed increasing trends.

Background: The allocation of resources between offspring size and number is a central question of life-history theory. Although several studies have tested the existence of this trade-off, few studies have investigated how envi-ronmental variation influences the allocation of resources to offspring size and offspring number. Additionally, the relationship between population dynamics and the offspring size and number allocation is far less understood. Methods: We investigate whether resource allocation between egg size and clutch size is influenced by the ambient temperature and whether it may be related to apparent nest survival rate. We measured 1548 eggs from 541 nests of two closely related shorebird species, the Kentish Plover (Charadrius alexandrinus) and the White-faced Plover (C. deal-batus) in China, in four populations that exhibit contrasting ambient environments. We weighed females, monitored nest survival, and calculated the variance of ambient temperature. Results: Although we found that egg size and clutch size were all different between the four breeding populations, the reproductive investment (i.e. total clutch volume) was similar between populations. We also found that popula-tions with a high survival rate had relatively larger eggs and a smaller clutch than populations with a low nest survival rate. The latter result is in line with a conservative/diversified bet-hedging strategy. Conclusions: Our findings suggest that plovers may increasing fitness by investing fewer, larger or many, small according local nest survival rate to make a similar investment in reproduction, and thereby may have an impact on population demography.

Background:Animals need to adjust their vigilance strategies when foraging between physically contrasting veg-etated and non-vegetated habitats.Vegetated habitats may pose a greater risk for some if vegetation characteristics function as a visual obstruction but benefit others if they serve as protective shelter.Variation in group size,presence of similar species,along with variation in environmental conditions and anthropogenic disturbance can also influence vigilance investment.Methods:In this study,we quantified the vigilance behaviour of two large-bodied,sympatric migratory curlew species—Far Eastern Curlew(Numenius madagascariensis)and Eurasian Curlew(N.arquata)—in vegetated Suaeda salsa saltmarsh and non-vegetated mudflat habitat in Liaohekou National Nature Reserve,China.We used linear mixed models to examine the effects of habitat type,season,tide time,flock size(conspecific and heterospecific),and human disturbance on curlew vigilance investment.Results:Both species spent a higher percentage of time under visual obstruction in S.salsa habitat compared to mudflat habitat but in response,only Far Eastern Curlew increased their percentage of vigilance time,indicating that visual obstruction in this habitat is only a concern for this species.There was no evidence that S.salsa vegetation served as a form of cryptic background colouration since neither species decreased their vigilance effect in S.salsa habitat in spring compared to the autumn migration season.The effect of curlew social environment(i.e.flock size)was habitat dependent since percentage of vigilance time by curlews in saltmarsh increased with both the number of individual curlews and number of other birds present,but not in mudflat habitat.Conclusions:We conclude that both migratory curlew species exhibit a flexible vigilance adjustment strategy to cope with the different environmental and social conditions of adjacent and sharply contrasting coastal habitats,and that the trade-off between the risks of foraging and the abundance of prey may be a relatively common phenom-enon in these and other shorebird populations.