Warming sea surface temperatures are linked to lower shorebird migratory fuel loads.

Warming sea surface temperatures (SSTs) are altering the biological structure of intertidal wetlands at a global scale, with potentially serious physiological and demographic consequences for migratory shorebird populations that depend on intertidal sites. The effects of mediating factors, such as age-related foraging skill, in shaping the consequences of warming SSTs on shorebird populations, however, remain largely unknown. Using morphological measurements of Dunlin fuelling for a >3000 km transoceanic migration, we assessed the influence of climatic conditions and age on individuals' migratory fuel loads and performance. We found that juveniles were often at risk of exhausting their fuel loads en route to primary wintering grounds, especially following high June SSTs in the previous year; the lagged nature of which suggests SSTs acted on juvenile loads by altering the availability of critical prey. Up to 45% fewer juveniles may have reached wintering grounds via a non-stop flight under recent high SSTs compared to the long-term trend. Adults, by contrast, were highly capable of reaching wintering grounds in non-stop flight across years. Our findings suggest that juveniles were disproportionately impacted by apparent SST-related declines in critical prey, and illustrate a general mechanism by which climate change may shape migratory shorebird populations worldwide.

A circumpolar study unveils a positive non-linear effect of temperature on arctic arthropod availability that may reduce the risk of warming-induced trophic mismatch for breeding shorebirds.

Seasonally abundant arthropods are a crucial food source for many migratory birds that breed in the Arctic. In cold environments, the growth and emergence of arthropods are particularly tied to temperature. Thus, the phenology of arthropods is anticipated to undergo a rapid change in response to a warming climate, potentially leading to a trophic mismatch between migratory insectivorous birds and their prey. Using data from 19 sites spanning a wide temperature gradient from the Subarctic to the High Arctic, we investigated the effects of temperature on the phenology and biomass of arthropods available to shorebirds during their short breeding season at high latitudes. We hypothesized that prolonged exposure to warmer summer temperatures would generate earlier peaks in arthropod biomass, as well as higher peak and seasonal biomass. Across the temperature gradient encompassed by our study sites (>10°C in average summer temperatures), we found a 3-day shift in average peak date for every increment of 80 cumulative thawing degree-days. Interestingly, we found a linear relationship between temperature and arthropod biomass only below temperature thresholds. Higher temperatures were associated with higher peak and seasonal biomass below 106 and 177 cumulative thawing degree-days, respectively, between June 5 and July 15. Beyond these thresholds, no relationship was observed between temperature and arthropod biomass. Our results suggest that prolonged exposure to elevated temperatures can positively influence prey availability for some arctic birds. This positive effect could, in part, stem from changes in arthropod assemblages and may reduce the risk of trophic mismatch.

A Review of the Conservation Status of Shorebirds in Mongolia.

We present the first comprehensive review of 62 migratory shorebird species in Mongolia, covering their ecological status, IUCN assessments at regional or national levels, population trends, threats, and conservation measures. Mongolia hosts a total of 62 shorebird species from twenty-two genera and seven families, with six species classified as globally threatened: the Critically Endangered Sociable Lapwing, the Endangered Siberian Sandplover, the Far Eastern Curlew, the Great Knot, and the Vulnerable Sharp-Tailed Sandpiper. Both national and global IUCN Red List assessments highlight Mongolia's significance as a breeding and passage migrating site for globally threatened and Near-Threatened shorebirds. Species richness is higher in northern regions compared to the south, with the highest diversity found in areas with complex aquatic ecosystems. Global population trends indicate a decline in 61% of species, with 18% remaining stable, 16% of unknown status, and 5% increasing. At the national level, most species are stable (61%), 34% status is unknown, and 5% are decreasing. Anthropogenic-induced threats, including habitat loss and degradation, pollution, disturbance, and harvesting, pose significant risks to 69% of species, while natural disasters affect 11%. Additionally, 8% of species are impacted by accidental mortality and intrinsic factors, and 5% by changes in native species. Despite these threats, no specific conservation action plans exist for shorebirds in Mongolia. However, general conservation measures are in place, such as environmental and fauna protection laws, regulations on foreign trade in endangered species, and the establishment of protected areas under governmental resolutions. Mongolia also participates in international conventions like the Convention on Biological Diversity (CBD), Ramsar, and Migratory Species (CMS), and has developed national red lists, red books, and publications such as "A Summary Conservation Action Plan for Mongolian Birds", "Important Bird Areas" to support conservation efforts.

Role-reversed polyandry is associated with faster fast-Z in shorebirds.

In birds, males are homogametic and carry two copies of the Z chromosome ('ZZ'), while females are heterogametic and exhibit a 'ZW' genotype. The Z chromosome evolves at a faster rate than similarly sized autosomes, a phenomenon termed 'fast-Z evolution'. This is thought to be caused by two independent processes-greater Z chromosome genetic drift owing to a reduced effective population size, and stronger Z chromosome positive selection owing to the exposure of partially recessive alleles to selection. Here, we investigate the relative contributions of these processes by considering the effect of role-reversed polyandry on fast-Z in shorebirds, a paraphyletic group of wading birds that exhibit unusually diverse mating systems. We find stronger fast-Z effects under role-reversed polyandry, which is consistent with particularly strong selection on polyandrous females driving the fixation of recessive beneficial alleles. This result contrasts with previous research in birds, which has tended to implicate a primary role of genetic drift in driving fast-Z variation. We suggest that this discrepancy can be interpreted in two ways-stronger sexual selection acting on polyandrous females overwhelms an otherwise central role of genetic drift, and/or sexual antagonism is also contributing significantly to fast-Z and is exacerbated in sexually dimorphic species.

Frequency-dependent tolerance to aircraft disturbance drastically alters predicted impact on shorebirds.

Anthropogenic disturbance of wildlife is increasing globally. Generalizing impacts of disturbance to novel situations is challenging, as the tolerance of animals to human activities varies with disturbance frequency (e.g. due to habituation). Few studies have quantified frequency-dependent tolerance, let alone determined how it affects predictions of disturbance impacts when these are extrapolated over large areas. In a comparative study across a gradient of air traffic intensities, we show that birds nearly always fled (80%) if aircraft were rare, while birds rarely responded (7%) if traffic was frequent. When extrapolating site-specific responses to an entire region, accounting for frequency-dependent tolerance dramatically alters the predicted costs of disturbance: the disturbance map homogenizes with fewer hotspots. Quantifying frequency-dependent tolerance has proven challenging, but we propose that (i) ignoring it causes extrapolations of disturbance impacts from single sites to be unreliable, and (ii) it can reconcile published idiosyncratic species- or source-specific disturbance responses.

Mercury and rare earth elements (REEs) show different spatial trends in feathers of Kentish plover (Charadrius alexandrinus) breeding along the Adriatic Sea coast, Italy.

Feather analysis is an ethical and effective method for assessing the exposure of wild birds to environmental contamination due to trace elements and organic pollutants. We used feather to monitor the exposure to three toxic and non-essential metals (Hg, Cd, and Pb) and rare earth elements (REEs) of Kentish plover (Charadrius alexandrinus) breeding in different coastal areas (Veneto, Emilia-Romagna, Marche, Abruzzo, and Apulia) along the Italian coast of the Adriatic Sea. Feathers (n = 113) were collected from April to June. Feather concentrations evidenced a significant exposure to Hg (13.05 ± 1.71 mg kg-1 dw) and REEs (447.3 ± 52.8 ng g-1 dw) in the Kentish plover breeding in Veneto (n = 21) compared to the other coastal areas, with several individuals showing Hg concentrations above the adverse effect (5 mg kg-1 dw) and high-risk (9.14 mg kg-1 dw) thresholds reported for birds. Higher REE concentrations compared to Marche (n = 29), Abruzzo (n = 11) and Apulia (n = 13) were also reported for birds breeding in Emilia-Romagna (474.9 ± 41.9 ng g-1 dw; n = 29). The exposure to Cd and Pb was low in all the coastal areas, and only a few samples (n = 6 and n = 4 for Cd and Pb, respectively) exceeded the adverse effect thresholds (0.1 and 4 mg kg-1 for Cd and Pb, respectively). A significant sex-related difference was observed for REE-concentrations, with females showing higher concentration than males. These data highlight the need to monitor the exposure of the Kentish plover to Hg and REEs, especially in the northern basin of the Adriatic Sea, since these elements might negatively affect species' reproductive success and threaten its conservation.

Why do avian responses to change in Arctic green-up vary?

Global climate change has altered the timing of seasonal events (i.e., phenology) for a diverse range of biota. Within and among species, however, the degree to which alterations in phenology match climate variability differ substantially. To better understand factors driving these differences, we evaluated variation in timing of nesting of eight Arctic-breeding shorebird species at 18 sites over a 23-year period. We used the Normalized Difference Vegetation Index as a proxy to determine the start of spring (SOS) growing season and quantified relationships between SOS and nest initiation dates as a measure of phenological responsiveness. Among species, we tested four life history traits (migration distance, seasonal timing of breeding, female body mass, expected female reproductive effort) as species-level predictors of responsiveness. For one species (Semipalmated Sandpiper), we also evaluated whether responsiveness varied across sites. Although no species in our study completely tracked annual variation in SOS, phenological responses were strongest for Western Sandpipers, Pectoral Sandpipers, and Red Phalaropes. Migration distance was the strongest additional predictor of responsiveness, with longer-distance migrant species generally tracking variation in SOS more closely than species that migrate shorter distances. Semipalmated Sandpipers are a widely distributed species, but adjustments in timing of nesting relative to variability in SOS did not vary across sites, suggesting that different breeding populations of this species were equally responsive to climate cues despite differing migration strategies. Our results unexpectedly show that long-distance migrants are more sensitive to local environmental conditions, which may help them to adapt to ongoing changes in climate.

Complete mitochondrial genome MK992912 of Great Knot (Calidris tenuirostris) is a chimera with DNA from Pacific Golden Plover Pluvialis fulva (Aves: Charadriiformes).

A complete mitochondrial genome of Great Knot (Calidris tenuirostris), MK992912, was published by He and colleagues in 2020. Here we show that this mitogenome is actually a chimera containing DNA fragments of both C. tenuirostris (15,567 bp, 92.8%) and Pacific Golden Plover (Pluvialis fulva, 1208 bp, 7.2%). Detecting such errors is possible before publication if each sequenced fragment is separately analyzed phylogenetically before assembling the fragments into a single mitogenome. This mitogenome has been re-used in at least four phylogenies. The error is documented to avoid the perpetuation of erroneous sequence information in the literature.

Environmental factors influencing red knot (Calidris canutus islandica) departure times of relocation flights within the non-breeding period.

Deciding when to depart on long-distance, sometimes global, movements can be especially important for flying species. Adverse weather conditions can affect energetic flight costs and navigational ability. While departure timings and conditions have been well-studied for migratory flights to and from the breeding range, few studies have focussed on flights within the non-breeding season. Yet in some cases, overwintering ranges can be large enough that ecological barriers, and a lack of resting sites en route, may resist movement, especially in unfavorable environmental conditions. Understanding the conditions that will enable or prohibit flights within an overwintering range is particularly relevant in light of climate change, whereby increases in extreme weather events may reduce the connectivity of sites. We tracked 495 (n = 251 in 2019; n = 244 in 2020) overwintering red knots (Calidris canutus islandica) in the Dutch Wadden Sea and investigated how many departed towards the UK (on westward relocation flights), which requires flying over the North Sea. For those that departed, we used a resource selection model to determine the effect of environmental conditions on the timing of relocation flights. Specifically, we investigated the effects of wind, rain, atmospheric pressure, cloud cover, and migratory timing relative to sunset and tidal cycle, which have all been shown to be crucial to migratory departure conditions. Approximately 37% (2019) and 36% (2020) of tagged red knots departed on westward relocation flights, indicating differences between individuals' space use within the overwintering range. Red knots selected for departures between 1 and 2.5 h after sunset, approximately 4 h before high tide, with tailwinds and little cloud cover. However, rainfall and changes in atmospheric pressure appear unimportant. Our study reveals environmental conditions that are important for relocation flights across an ecological barrier, indicating potential consequences of climate change on connectivity.

Stopover habitat selection drives variation in the gut microbiome composition and pathogen acquisition by migrating shorebirds.

Long-distance host movements play a major regulatory role in shaping microbial communities of their digestive tract. Here, we studied gut microbiota composition during seasonal migration in five shorebird species (Charadrii) that use different migratory (stopover) habitats. Our analyses revealed significant interspecific variation in both composition and diversity of gut microbiome, but the effect of host identity was weak. A strong variation in gut microbiota was observed between coastal and inland (dam reservoir and river valley) stopover habitats within species. Comparisons between host age classes provided support for an increasing alpha diversity of gut microbiota during ontogeny and an age-related remodeling of microbiome composition. There was, however, no correlation between microbiome and diet composition across study species. Finally, we detected high prevalence of avian pathogens, which may cause zoonotic diseases in humans (e.g. Vibrio cholerae) and we identified stopover habitat as one of the major axes of variation in the bacterial pathogen exposure risk in shorebirds. Our study not only sheds new light on ecological processes that shape avian gut microbiota, but also has implications for our better understanding of host-pathogen interface and the role of birds in long-distance transmission of pathogens.

Spatial synchrony cascades across ecosystem boundaries and up food webs via resource subsidies.

Cross-ecosystem subsidies are critical to ecosystem structure and function, especially in recipient ecosystems where they are the primary source of organic matter to the food web. Subsidies are indicative of processes connecting ecosystems and can couple ecological dynamics across system boundaries. However, the degree to which such flows can induce cross-ecosystem cascades of spatial synchrony, the tendency for system fluctuations to be correlated across locations, is not well understood. Synchrony has destabilizing effects on ecosystems, adding to the importance of understanding spatiotemporal patterns of synchrony transmission. In order to understand whether and how spatial synchrony cascades across the marine-terrestrial boundary via resource subsidies, we studied the relationship between giant kelp forests on rocky nearshore reefs and sandy beach ecosystems that receive resource subsidies in the form of kelp wrack (detritus). We found that synchrony cascades from rocky reefs to sandy beaches, with spatiotemporal patterns mediated by fluctuations in live kelp biomass, wave action, and beach width. Moreover, wrack deposition synchronized local abundances of shorebirds that move among beaches seeking to forage on wrack-associated invertebrates, demonstrating that synchrony due to subsidies propagates across trophic levels in the recipient ecosystem. Synchronizing resource subsidies likely play an underappreciated role in the spatiotemporal structure, functioning, and stability of ecosystems.

Assessing shorebird mortalities due to razor clam aquaculture at key migratory stopover sites in southeastern China.

Aquaculture can provide foraging habitat for birds, but it can also result in intentional and accidental mortality. We examined an overlooked conflict between razor clam (Sinonovacula spp.) aquaculture and declining shorebirds in southeastern China's Fujian and Zhejiang provinces. We surveyed 6 out of 11 internationally important stopover sites for these shorebirds and monitored shorebird mortality in 2 sites (Xinghua Bay, Yueqing Bay) with razor clam aquaculture. We visited an additional 32 sites in these 2 provinces to determine if there was netting in other razor clam farms. Approximately 8-9 km2 of intertidal foraging habitat was covered by horizontal nets to prevent birds from feeding on young razor clams at Xinghua Bay and Yueqing Bay. We conservatively estimated that 13,676 (2.5th-97.5th percentile 8,330-21,285) individual shorebirds were entangled in the nets at the 2 monitored sites in April and May 2021, including 2 endangered and 7 near-threatened species. Mortality of 5 species for which we had sufficient data accounted for 0.76% (black-tailed godwit [Limosa limosa]) to 4.27% (terek sandpiper [Xenus cinereus]) of their total flyway populations. This level of mortality could strongly affect their populations. We found netting at 17 additional razor clam farms, indicating a widespread threat to shorebirds. Although razor clams are typically harvested in late March to early April, nets are left on the mudflats throughout the spring and summer, including when the bulk of shorebird migration takes place. Immediately removing these nets after the clam harvest could prevent most of the spring mortality of shorebirds, although this is unlikely to happen without government regulations or economic incentives. To better assess and mitigate the impacts of this conflict, future research should quantify shorebird mortality at other razor clam farms, including during winter, explore less harmful deterrence methods, and assess the socioeconomic factors driving the conflict.

Evaluación de la mortalidad de aves costeras causada por la acuacultura de almejas navaja en sitios importantes de descanso migratorio en el sureste de China Resumen La acuacultura puede proporcionar hábitats de forrajeo para las aves, pero también puede derivar en muertes accidentales o intencionales. Analizamos un conflicto ignorado entre la acuacultura de almeja navaja (Sinonovacula spp.) y la declinación de aves costeras en las provincias de Fujian y Zhejiang del sureste de China. Censamos seis de los once sitios de descanso con importancia internacional para estas aves y monitoreamos su mortalidad en dos sitios en donde se cría la almeja navaja: la bahía de Xinghua y la de Yueqing. Además, visitamos 32 sitios en estas dos provincias para determinar si existían redes en otras granjas de almeja navaja. Unos 8 ­ 9 km2 del hábitat intermareal de forrajeo estaban cubiertos por redes horizontales para evitar que las aves se alimentaran de las almejas juveniles en ambas bahías. Estimamos moderadamente que 13,676 (2.5° ­ 97.5° percentil 8,330 ­ 21,285) individuos de aves costeras se enredaron en las redes en los dos sitios monitoreados durante abril y mayo de 2021, incluyendo a dos especies en peligro y siete casi amenazadas. La mortalidad de las cinco especies para las cuales tuvimos suficientes datos representó del 0.76% (Limosa limosa) al 4.27% (Xenus cinereus) del total de las poblaciones migratorias. Este nivel de mortalidad podría tener un gran efecto sobre las poblaciones de estas especies. Encontramos redes en 17 granjas más, lo que indica una amenaza extendida para las aves costeras. Aunque es típico que se colecte la almeja navaja a finales de marzo y principios de abril, las redes permanecen durante toda la primavera y el verano, incluso cuando ocurre la mayoría de los vuelos migratorios. La eliminación inmediata de estas redes después de la colecta de almejas podría prevenir la mayoría de las muertes primaverales de las aves costeras, aunque no es probable que esto suceda sin regulaciones gubernamentales o incentivos económicos. Para tener mejores evaluaciones y mitigaciones del impacto de este conflicto, una investigación más profunda debería cuantificar la mortalidad de las aves costeras en otras granjas, incluso durante el invierno, explorar métodos de disuasión menos dañinos y evaluar los factores socioeconómicos que causan el conflicto.

The threat of microplastics: Exploring pollution in coastal ecosystems and migratory shorebirds along the west coast of India.

To evaluate the exposure risk and ingestion of microplastics by migratory shorebirds, which are regarded as apex predators in the coastal ecosystem, this study investigated the ubiquitous presence of microplastics in estuarine and coastal habitats and their potential to be transferred in the food chains. We analysed the presence of microplastics in water, sediment, major macroinvertebrate prey and the guano samples of ten shorebird species from ten important wintering grounds in the west coast of India. Our results revealed that water is the primary source through which microplastics disseminate into various ecosystem components. Microplastic debris in various forms were reported in all samples analysed, with microfibres being the most abundant form. While polyethylene and polypropylene were found as the major microplastic types in water, sediment, and prey samples, polystyrene was most abundant in guano samples. Microplastic transfer and impacts in this delicate ecosystem demand further investigations.

Individuals of a group-living shorebird show smaller home range overlap when food availability is low.

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.

Heavy metals in wetlands of southwestern India: from sediments through invertebrates to migratory shorebirds.

Heavy metal pollution in Indian wetlands is rising due to industrial, agricultural and urban development activities. Shorebirds occupy upper trophic levels and are therefore especially vulnerable to heavy metal pollution. We evaluated the concentration of heavy metals (zinc, copper, cobalt, chromium, lead and cadmium) in 22 common species of migrant shorebirds (220 shorebird dropping samples) with diverse foraging behaviors, in their different prey (55 prey samples) and in the sediments (90 sediment samples) in different habitat types (mudflats, mangroves and sand beaches) between 2019 and 2021. Further, we analyzed a total of 10 biofilm samples from mudflats and mangroves. We detected relatively low concentrations of heavy metals in the sediments (Zn concentration range: 9.11-40.91 mg/kg; Cu: 5.74-21.38 mg/kg; Co: 2.00-4.04 mg/kg; Cr: 4.05-41.03 mg/kg; Pb: 1.02-7.19 mg/kg; Cd: 0.56-4.35 mg/kg). However, we measured relatively high concentrations of heavy metals in invertebrate prey species (Zn concentration range: 84.72-224.74 mg/kg; Cu: 26.63-170.36 mg/kg; Co: 13.98-14.42 mg/kg; Cr: 14.78-98.16 mg/kg; Pb: 18.95-157.29 mg/kg; Cd: 9.33-60.56 mg/kg). In addition, we found high concentrations of heavy metals in shorebird droppings (Zn concentration range: 41.33-58.8 mg/kg; Cu: 31.42-52.11 mg/kg; Co: 36.34-55.68 mg/kg; Cr: 52.3-68.21 mg/kg; Pb: 25.94-43.13 mg/kg; Cd: 5.53-16.4 mg/kg). It is evident that concentration of heavy metals increased successively moving from sediment to prey to shorebird species, likely through trophic transfer. The biofilm samples contained very high concentrations of Cr, Pb and Cd (22.64, 28.09 and 18.46 mg/kg respectively) which could be harmful to biofilm grazing shorebirds. Since bioaccumulation of heavy metals entail risks in living species, we suggest that increasing concentrations may detrimentally affect physiological processes in invertebrates and shorebirds. There is an urgent need to identify the sources of pollution and to reduce the discharge of heavy metals and other pollutants into coastal and inland wetlands.

An impact evaluation of conservation investments targeting long-distance migratory species.

We evaluated the impact of a philanthropic program investing in the conservation of sites along the Pacific Americas Flyway, which spans >16,000 km of coastline and is used by millions of shorebirds. Using a quasi-experimental, mixed methods approach, we estimated what would have happened to shorebird populations at 17 wintering sites without the sustained and additional investment they received. We modeled shorebird populations across the entire flyway and at sites with and without investment. Combining shorebird abundance estimates with a land-cover classification model, we used the synthetic control method to create counterfactuals for shorebird trends at the treatment sites. We found no evidence of an overall effect across three outcome variables. Species- and site-level treatment effects were heterogeneous, with a few cases showing evidence of a positive effect, including a site with a high level of overall investment. Results suggest six shorebirds declined across the entire flyway, including at many Latin American sites. However, the percentage of flyway populations present at the sites remained stable, and the percentage at the treatment sites was higher (i.e., investment sites) than at control sites. Multiple mechanisms behind our results are possible, including that investments have yet to mitigate impacts and negative impacts at other sites are driving declines at the treatment sites. A limitation of our evaluation is the sole focus on shorebird abundance and the lack of data that prohibits the inclusion of other outcome variables. Monitoring infrastructure is now in place to design a more robust and a priori shorebird evaluation framework across the entire flyway. With this framework, it will prove easier to prioritize limited dollars to result in the most positive conservation outcomes.

Evaluación del impacto de la inversión para la conservación enfocada en especies migratorias de largo recorrido Resumen Evaluamos el impacto de un programa filantrópico que invierte en la conservación de sitios a lo largo de la Ruta Migratoria Pacífico-Américas, la cual abarca >16,000 km de la línea costera y millones de aves playeras la usan. Estimamos con una estrategia cuasiexperimental y de métodos mixtos lo que habría pasado con las poblaciones de estas aves en 17 sitios invernales sin la inversión adicional y continua que recibieron. Modelamos estas poblaciones en toda la ruta y en sitios con y sin inversión. Combinamos las estimaciones de aves playeras con el modelo de clasificación de la cobertura del suelo y usamos el método de control sintético para crear contrafactuales para las tendencias de las aves playeras en sitios de tratamiento. No encontramos evidencia alguna de un efecto generalizado en las tres variables de los resultados. Los efectos del tratamiento de especies y de sitio fueron heterogéneos, con unos cuantos casos que mostraron evidencia de un efecto positivo, incluido un sitio con un nivel elevado de inversión general. Los resultados sugieren que seis especies de aves playeras declinaron a lo largo de toda la ruta, incluyendo en varios sitios de América Latina. Sin embargo, el porcentaje de poblaciones de la ruta presentes en los sitios permaneció estable y el porcentaje en los sitios de tratamiento (sitios de inversión) fue más elevado que en los sitios control. Muchos mecanismos son posibles detrás de nuestros resultados, incluidas las inversiones que todavía no han mitigado impactos y los impactos negativos en otros sitios que están causando las declinaciones en los sitios de tratamiento. Una limitación en nuestra evaluación es el enfoque único en la abundancia de aves playeras y la falta de datos que impiden la inclusión de otras variables de los resultados. El monitoreo de la infraestructura ahora está en una posición en la que puede diseñar un marco de evaluación más robusto y a priori de las aves playeras a lo largo de toda la ruta. Con este marco, será más fácil priorizar los dólares limitados para que los resultados de conservación sean lo más positivos posible.

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.

Assessment of contaminants, health and survival of migratory shorebirds in natural versus artificial wetlands - The potential of wastewater treatment plants as alternative habitats.

The rapid destruction of natural wetland habitats over past decades has been partially offset by an increase in artificial wetlands. However, these also include wastewater treatment plants, which may pose a pollution risk to the wildlife using them. We studied two long-distance Arctic-breeding migratory shorebird species, curlew sandpiper (Calidris ferruginea, n = 69) and red-necked stint (Calidris ruficollis, n = 103), while on their Australian non-breeding grounds using an artificial wetland at a wastewater treatment plant (WTP) and a natural coastal wetland. We compared pollutant exposure (elements and per- and poly-fluoroalkyl substances/PFASs), disease (avian influenza), physiological status (oxidative stress) of the birds at the two locations from 2011 to 2020, and population survival from 1978 to 2019. Our results indicated no significant differences in blood pellet pollutant concentrations between the habitats except mercury (WTP median: 224 ng/g, range: 19-873 ng/g; natural wetland: 160 ng/g, 22-998 ng/g) and PFASs (total PFASs WTP median: 85.1 ng/g, range: <0.01-836 ng/g; natural wetland: 8.02 ng/g, <0.01-85.3 ng/g) which were higher at the WTP, and selenium which was lower at the WTP (WTP median: 5000 ng/g, range: 1950-34,400 ng/g; natural wetland: 19,200 ng/g, 4130-65,200 ng/g). We also measured higher blood o,o'-dityrosine (an indicator of protein damage) at the WTP. No significant differences were found for adult survival, but survival of immature birds at the WTP appeared to be lower which could be due to higher dispersal to other wetlands. Interestingly, we found active avian influenza infections were higher in the natural habitat, while seropositivity was higher in the WTP, seemingly not directly related to pollutant exposure. Overall, we found limited differences in pollutant exposure, health and survival of the shorebirds in the two habitats. Our findings suggest that appropriately managed wastewater treatment wetlands could provide a suitable alternative habitat to these migratory species, which may aid in curbing the decline of shorebird populations from widespread habitat loss.

The Effects of Climate Change on the Nesting Phenology of Three Shorebird Species in the United States.

Previous research suggests that a frequent response of organisms to the ongoing climate crisis is the adjustment of their reproductive timing or breeding phenology. Shorebirds may be especially vulnerable to increasing temperatures and precipitation, as many are migratory and depend on coastal habitats for wintering and breeding. These particular habitats could be at risk due to changes in climate, and nesting times often depend on food availability, which is often directly influenced by temperature. We investigated if clutch initiation dates (CID) for three shorebird species in the United States have become earlier over time with increasing temperatures and precipitation. We used nest records from Cornell's NestWatch program and various museum databases and weather station data from the National Oceanic and Atmospheric Administration. We found evidence that CIDs have become earlier over time, though this was only a significant factor for one species. While temperature in our study areas has increased significantly over time, precipitation changes were more variable and not always significantly predicted by time. We found evidence that one species may be responding to increasing temperatures by nesting earlier, but there was no support for our hypothesis that CID has changed due to changes in precipitation for any species. Results varied for each species, indicating the importance of further studies on shorebirds as the effects of climate change on their nesting phenology may not be fully realized and will likely depend on the species' biology and distribution.