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

Vanellus vanellus (Linnaeus, 1758) (Aves, Charadriidae), Northern Lapwing, is listed as Near Threatened by the IUCN due to declines in the availability of its habitat since 1980. The species is a widespread Palearctic breeder and an uncommon migrant to Southeast Asia, where it winters in Thailand and Vietnam. We document the first recorded sighting of V. vanellus in Malaysia, marking the southernmost occurrence of the species to date.

Migratory shorebirds have many unique life history characteristics, such as long‐distance travel between breeding sites, stopover sites, and wintering sites. The physiological challenges for migrant energy requirement and immunity may affect their gut microbiome community. Here, we reviewed the specific features (e.g., relatively high proportion of Corynebacterium and Fusobacterium) in the gut microbiome of 18 migratory shorebirds, and the factors (e.g., diet, migration, environment, and phylogeny) affecting the gut microbiome. We discussed possible future studies of the gut microbiome in migratory shorebirds, including the composition and function of the spatial‐temporal gut microbiome, and the potential contributions made by the gut microbiome to energy requirement during migration. We synthesised published 16S rRNA gene data in the migratory shorebirds (Cho & Lee, 2020; Grond et al., 2019, 2020; Risely et al., 2017, 2018), and found the predominant phyla of these 13 shorebird species include Firmicutes, Bacteroidetes, Proteobacteria, Fusobacteria, and Actinobacteria.

Worldwide, shorebirds are some of the most endangered migratory species, especially the rufa Red Knot (Calidris canutus). Global change (e.g., human development, habitat loss, climate variability, sea level rise) has a significant impact on Red Knot populations, generating threats throughout their flyway. Since the initial decline of Red Knot populations in the late 1990s, research has been conducted to understand the threats Red Knots face and inform management actions to protect and aid in the recovery of these migratory birds. Shorebird physiology, especially for Red Knots, however, places limitations on attachment methods for long retention of tags. For this reason, we report on the novel use of satellite tags attached to Red Knots in the Atlantic Flyway using a new glue and suture method and describe this new methodology for tag attachment. Our results showed that tags attached with the glue and suture method versus only glue stayed on the bird 142% longer in year 1 and 162–320% longer in year 2 (depending on the tag type), with a tag retention time of up to 5 months. The glue and suture attachment method is a successful tag attachment method for migratory shorebirds, especially for species where other methods cause adverse effects. This method provides long-term retention of the tag without causing negative impacts to migration, survival, or breeding. With advances in transmitter technology, this is the best available method for longer retention time for these satellite tags. Mundialmente, las aves playeras son unas de las especies migratorias en mayor peligro, especialmente el correlimo Calidris canutus rufa. El cambio global (por ejemplo desarrollo humano, pérdida de hábitat, variabilidad climática, aumento de nivel del mar) tiene un impacto significativo en poblaciones del correlimo Calidris canutus rufa, produciendo amenazas a través de su ruta migratoria. Desde el declive inicial de las poblaciones de correlimo Calidris canutus rufa a finales de los 1990s, se han realizado investigaciones para entender las amenazas que enfrentan los correlimos Calidris canutus rufa y informar a los tomadores de decisiones para la toma de decisiones de manejo para proteger y ayudar a la recuperación de estas aves migratorias. Sin embargo, la fisiología de las aves playeras, especialmente de los correlimo Calidris canutus rufa, limita los métodos de marcaje para la retención de las marcas por largos periodos. Por esta razón, reportamos el nuevo método de marcaje satelital en correlimo Calidris canutus rufa en la ruta migratoria del Atlántico usando un nuevo método de pegamento y sutura y describiendo el nuevo método de unión de marcas. Nuestros resultados mostraron que las marcas unidas con el método de pegamento y sutura versus solo pegamento permaneció en el ave un 142% más tiempo en el año 1 y 162–320% más tiempo en el año 2 (dependiendo del tipo de marca), con retención de marcas hasta por 5 meses. El método de pegamento y sutura es un método exitoso de unión de marca para aves playeras migratorias, especialmente para especies en las que otros métodos pueden causar efectos adversos. Este método proporciona retención de la marca a largo plazo sin causar impactos negativos en la migración, la sobrevivencia o la reproducción. Con avances en la tecnología de transmisores, este es el mejor método disponible para un mayor tiempo de retención de estas marcas satelitales. Palabras clave: aves playeras migratorias, conservación, monitoreo satelital, uniones con pegamento y sutura.

Food webs and trophic dynamics of coastal systems have been the focus of intense research throughout the world, as they prove to be critical in understanding ecosystem processes and functions. However, very few studies have undertaken a quantitative comparison of entire food webs from a key consumer perspective across a broad geographical area, limiting relevant comparisons among systems with distinct biotic and abiotic components. We investigate the structure and functioning of food webs in four tidal ecosystems of international importance for migratory shorebirds along the East Atlantic Flyway: Tejo estuary in Portugal, Sidi Moussa in Morocco, Banc d'Arguin in Mauritania and Bijagós archipelago in Guinea‐Bissau. Basal food sources, shorebirds and their prey (benthic invertebrates) were sampled in all areas, and Bayesian stable isotope mixing models and community‐wide metrics were used in a comparative analysis among areas. Significant differences among study areas were found in the structure of food webs, as well as in the relative importance of basal resource pools supporting each food web. Overall, the food web of Banc d'Arguin was characterized by lower trophic diversity and higher functional redundancy than the other sites. This result might be explained by the low number of trophic pathways of organic matter transfer in this seagrass‐dominated system which, as a fossil estuary, lacks inputs from both freshwater and nutrient‐rich offshore oceanic waters. Structure of shorebird communities was consistent with the main organizational patterns found for each food web, highlighting the less diverse character of the community of Banc d'Arguin. At Banc d'Arguin and Bijagós archipelago, which displayed the smallest and largest isotopic niche widths in bird assemblage, respectively, mean niche overlap among species was low, suggesting high interspecific partitioning in resource use. Tropical systems typically offer comparatively lower harvestable prey biomass for shorebirds and might thus strengthen interspecific competition, leading to low niche overlap among species. Our study reveals relevant differences in the structure of food webs and shorebird communities in coastal areas along an avian flyway. While differences in trophic redundancy of food webs point to distinct levels of ecosystem resilience, contrasts in the organization of shorebird communities highlight the plasticity in the foraging behaviour of species inhabiting areas with distinct environmental conditions.

Every year, millions of migratory shorebirds fly through the East Asian-Australasian Flyway between their arctic breeding grounds and Australasia. This flyway includes numerous coastal wetlands in Asia and the Pacific that are used as stopover sites where birds rest and feed. Loss of a few important stopover sites through sea-level rise (SLR) could cause sudden population declines. We formulated and solved mathematically the problem of how to identify the most important stopover sites to minimize losses of bird populations across flyways by conserving land that facilitates upshore shifts of tidal flats in response to SLR. To guide conservation investment that minimizes losses of migratory bird populations during migration, we developed a spatially explicit flyway model coupled with a maximum flow algorithm. Migratory routes of 10 shorebird taxa were modeled in a graph theoretic framework by representing clusters of important wetlands as nodes and the number of birds flying between 2 nodes as edges. We also evaluated several resource allocation algorithms that required only partial information on flyway connectivity (node strategy, based on the impacts of SLR at nodes; habitat strategy, based on habitat change at sites; population strategy, based on population change at sites; and random investment). The resource allocation algorithms based on flyway information performed on average 15% better than simpler allocations based on patterns of habitat loss or local bird counts. The Yellow Sea region stood out as the most important priority for effective conservation of migratory shorebirds, but investment in this area alone will not ensure the persistence of species across the flyway. The spatial distribution of conservation investments differed enormously according to the severity of SLR and whether information about flyway connectivity was used to guide the prioritizations. With the rapid ongoing loss of coastal wetlands globally, our method provides insight into efficient conservation planning for migratory species. Cada año, millones de aves costeras migratorias vuelan por la ruta migratoria Asia-Australasia de Oriente entre sus sitios árticos de reproducción y Australasia. Esta ruta incluye numerosos humedales costeros en Asia y el Pacífico que se usan como sitios de parada temporal donde las aves descansan y se alimentan. La pérdida de unos cuántos sitios de parada temporal por medio del incremento en el nivel del mar (SLR, en inglés) podría causar declinaciones poblacionales repentinas. Formulamos y resolvimos matemáticamente el problema de cómo identificar los sitios de paradas temporales más importantes para minimizar las pérdidas de poblaciones de aves a lo largo de rutas migratorias al conservar suelos que faciliten cambios orilla arriba de llanuras de marea en respuesta al SLR. Para guiar una inversión en la conservación que minimice la pérdida de poblaciones de aves migratorias durante la migración, desarrollamos un modelo de ruta migratoria espacialmente explícito acoplado con un algoritmo de flujo máximo. Las rutas migratorias de 10 taxones de aves costeras fueron modeladas en el marco de la teoría de gráficos al representar agrupaciones de humedales importantes como nodos y los números de aves volando entre 2 nodos como bordes. También evaluamos varios algoritmos de asignación de recursos que requirieron sólo información parcial sobre la conectividad de rutas migratorias (estrategia de nodo, basada en los impactos del SLR en los nodos; estrategia de hábitat, basada en cambios de hábitat en los sitios; estrategia de población, basada en cambios de población en los sitios; e inversión al azar). El algoritmo de asociación de recursos basado en la información de rutas migratorias se desempeñó en promedio 15% mejor que las asignaciones simples basadas en patrones de pérdida de hábitat o conteos locales de aves. La región del Mar Amarillo sobresalió como la prioridad más importante para la conservación efectiva de aves costeras migratorias, pero sólo la inversión en el área no puede asegurar la persistencia de especies a lo largo de la ruta migratoria. La distribución espacial de las inversiones de conservación difiere enormemente de acuerdo a la severidad del SLR y dependiendo de si la información sobre la conectividad de las rutas migratorias se usó para guiar las priorizaciones. Con la continua y rápida pérdida de humedales costeros a nivel global, nuestro método proporciona conocimiento sobre la planeación eficiente de la conservación para especies migratorias.

Understanding the social acceptability of biodiversity offsets is important to the design of offset policy. We used a discrete choice experiment to quantify preferences of Australians for a migratory shorebird offset in the context of an oil and gas development project. We surveyed a nationally representative sample of 1371 respondents on their preferences for current and prospective offset-policy characteristics via an online questionnaire to inform policy design of the social dimensions related to offset acceptability. The majority of respondents accepted offsetting as a means to allow economic development; the option to reject development (and an offset) was selected in 13% of possible offset scenarios. Substituting protection of a species affected by the development with protection of a more endangered species was a desirable policy characteristic, as was having the offset implemented by a third party or the government rather than the company responsible for the development. Direct offset activities (e.g., improving degraded habitat) were preferred over indirect activities (e.g., a research program), and respondents were strongly against locating the offset at a site other than where the impact occurred. Positive and negative characteristics of offsets could be traded off by changing the number of birds protected by the offset. Our results show that Australians are likely to support increased flexibility in biodiversity-offset policies, particularly when undesirable policy characteristics are compensated for. Entender la aceptabilidad social de las compensaciones de la biodiversidad es importante para diseñar una política de compensaciones. Utilizamos un experimento de opción discreta para cuantificar las preferencias de los australianos por una compensación de aves costeras migratorias en el contexto de un proyecto de desarrollo de gas y petróleo. Encuestamos una muestra representativa nacionalmente de 1371 respondientes sobre sus preferencias por las características actuales y futuras de la política de compensaciones por medio de un cuestionario en línea para informar al diseño de la politica sobre las dimensiones sociales relacionadas con la aceptabilidad de la compensación. La mayoría de los respondientes aceptaron la compensación como un medio para permitir el desarrollo económico; la opción de rechazar el desarrollo de gas y petróleo (y una compensación) fue seleccionada en 13 % de los posibles escenarios de compensación. Sustituir la protección de una especie afectada por el desarrollo con la protección de más especies en peligro fue una característica deseable de la política, así como la implementación de la compensación por parte de un tercero o el gobierno en lugar de la compañía responsable del desarrollo. Las actividades directas de compensación (P. ej.: mejor el habitat degradado) fueron preferidas por encima de las actividades indirectas (P. ej.: un programa de investigación) y los respondientes estuvieron ampliamente en contra de ubicar a la compensación en un sitio distinto a donde ocurre el impacto. Las características positivas y negativas de las compensaciones podrían intercambiarse modificando el número de aves protegidas por la compensación. Nuestros resultados muestran que los australianos probablemente apoyen un incremento en la flexibilidad de las políticas de compensación de la biodiversidad, particularmente cuando se compensan las características indeseables de la política.

Background Group living animals, such as shorebirds foraging on intertidal mudflats, may use social information about where to find hidden food items. However, flocking also increases intraspecific competition for resources, which may be exacerbated by food scarcity. Therefore, although aggregation may bring benefits, it may also increase the intensity of intraspecific competition. Methods We examined this trade-off in adult great knots Calidris tenuirostris , a molluscivorous long-distance migrating shorebird species, using interannual variation based on 2 years with different levels of food availability during their northward migratory staging in the northern Yellow Sea, China. We estimated individual home ranges and the extent of spatial overlap of home ranges of individually tagged birds in 2012 and 2015, whilst discounting for possible differences in body size, body mass, sex and migration schedule between years. Results We found that home range size was not associated with body mass, arrival date, body size, or sex of the individual. Despite a significant difference in food availability between the two study years, there was no significant change in the 50% and 95% home range size of great knots in the contrasting situations. However, there was a significantly smaller spatial overlap between individuals in the year when food was less available, suggesting that great knots operated more independently when food was scarce than when it was abundant. Conclusions These results suggest that minimizing intraspecific competition became more important when food was scarce. Where it is impossible to monitor all habitats en route , monitoring the local movements of shorebirds may offer a way to detect changes in habitat quality in real time.

Inherent tradeoffs exist between survey effort and accuracy, with major implications for the design of effective monitoring programs as budgets and available resources influence both uncertainty and statistical power. Migratory shorebirds are experiencing population declines across their range; thus, effective monitoring is critical to understand drivers of migration chronologies, population dynamics, and biological response to restoration. In this study, we investigated how survey frequency may influence data uncertainty in migratory shorebird response to management actions at the Heʻeia National Estuarine Research Reserve (NERR), where stewards are interested in the long‐term impacts of decisions that affect three species of shorebirds: ʻAkekeke (Arenaria interpres); Kōlea (Pluvialis fulva); and ʻŪlili (Tringa incana). We co‐developed a high‐effort monitoring protocol with site partners and modeled how well reduced survey frequencies captured occupancy dynamics and the variability in species counts observed under our full protocol. We found no difference in relative accuracy between surveys made once and twice a month, indicating that person‐hours spent monitoring at this site could be halved without exceeding acceptable uncertainty thresholds for long‐term management. Shorebirds varied in their habitat preferences, suggesting that individual species preferences should be considered when restoring or protecting habitat for a mixed assemblage. While ʻAkekeke and ʻŪlili used tidally limited habitat, Kōlea were observed to be wide generalists occurring throughout the reserve boundaries. This study provides a model for a relatively low‐investment strategy to inform survey design for monitoring low‐abundance or seasonally variable species of management interest. We examined how survey frequency affects data uncertainty in monitoring migratory shorebirds at the Heʻeia National Estuarine Research Reserve, where managers are interested in how restoration actions impact three species with varying habitat use trends. By modeling reduced survey frequencies against a high‐effort baseline dataset, we quantified variability in species occupancy to inform site‐specific long‐term monitoring design. This approach provides decision‐makers with a framework for calibrating survey frequency based on site‐specific management objectives and tolerance for uncertainty.

To identify areas on the landscape that may contribute to a robust network of conservation areas, we modeled the probabilities of occurrence of several en route migratory shorebirds and wintering waterfowl in the southern Great Plains of North America, including responses to changing climate. We predominantly used data from the eBird citizen‐science project to model probabilities of occurrence relative to land‐use patterns, spatial distribution of wetlands, and climate. We projected models to potential future climate conditions using five representative general circulation models of the Coupled Model Intercomparison Project 5 (CMIP5). We used Random Forests to model probabilities of occurrence and compared the time periods 1981–2010 (hindcast) and 2041–2070 (forecast) in “model space.” Projected changes in shorebird probabilities of occurrence varied with species‐specific general distribution pattern, migration distance, and spatial extent. Species using the western and northern portion of the study area exhibited the greatest likelihoods of decline, whereas species with more easterly occurrences, mostly long‐distance migrants, had the greatest projected increases in probability of occurrence. At an ecoregional extent, differences in probabilities of shorebird occurrence ranged from −0.015 to 0.045 when averaged across climate models, with the largest increases occurring early in migration. Spatial shifts are predicted for several shorebird species. Probabilities of occurrence of wintering Mallards and Northern Pintail are predicted to increase by 0.046 and 0.061, respectively, with northward shifts projected for both species. When incorporated into partner land management decision tools, results at ecoregional extents can be used to identify wetland complexes with the greatest potential to support birds in the nonbreeding season under a wide range of future climate scenarios. To identify areas on the landscape that may contribute to a robust network of conservation areas, we modeled the probabilities of occurrence of several en route migratory shorebirds and wintering waterfowl in the southern Great Plains of North America, including responses to changing climate. Projected changes in shorebird probabilities of occurrence varied with species‐specific general distribution pattern, migration distance, and spatial scale. At an ecoregional extent, probabilities of shorebird occurrence averaged across climate models ranged from −0.015 to 0.045, and spatial shifts are predicted for several shorebird species. When incorporated into partner land management decision tools, results at ecoregional extents can be used to identify wetland complexes with the greatest potential to support birds in the nonbreeding season under a wide range of future climate scenarios. Photo by Joel Jorgensen.