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.

Review of contaminant levels and effects in shorebirds: Knowledge gaps and conservation priorities.

Environmental pollution has emerged as a major threat to bird populations. Many shorebird populations are declining, although contamination has been documented in some shorebirds, evidence of negative impacts is sparse and this important topic remains understudied. To guide future research and develop effective conservation strategies, we carried out a comprehensive review of environmental pollutants and their consequences on shorebirds. In total, we found 93 relevant articles which examined pollutant contamination in ~37% (79 of 215) of all shorebird species, mostly from the Charadriidae and Scolopacidae families. Studies were geographically biased: the majority were conducted in American flyways, while only 1 was found from Australasia and few were conducted in Asian flyways. The main geographic gap for research includes East Africa, South Asia and Siberian Arctic. The most well-documented pollutants included mercury (Hg, 37 studies), cadmium (33), and lead (Pb, 28); less well studied pollutants were barium (1), calcium (1), strontium (1), dicofols (1), and other newly emerging contaminants, such as plastic debris/microplastics (4) and antibiotics resistance (2). Several pollutants have caused considerable concerns in shorebirds, including embryotoxicity caused by PCBs at non-optimum temperature (laboratory experiments); reduced reproduction performance linked to maternal Hg and paternal Pb (field evidence); and reduced refueling and flight performance related to oil contamination (both field and laboratory evidence). Our results confirm that an in-depth understanding of the local, regional and global factors that influence population trends of shorebirds in light of increasing pollution threats is essential for accurate and effective management and conservation strategies.

Global population trends in shorebirds: migratory behaviour makes species at risk.

Linking population trends to species' traits is informative for the detection of the most important threatening factors and for assessing the effectiveness of conservation measures. Although some previous studies performed such an analysis at local to continental scales, the global-scale focus is the most relevant for conservation of the entire species. Here we evaluate information on global population trends of shorebirds, a widely distributed and ecologically diversified group, where some species connect different parts of the world by migration, while others are residents. Nowadays, shorebirds face rapid environmental changes caused by various human activities and climate change. Numerous signs of regional population declines have been recently reported in response to these threats. The aim of our study was to test whether breeding and non-breeding habitats, migratory behaviour (migrants vs. residents) and migration distance, breeding latitude, generation time and breeding range size mirror species' global population trends. We found that a majority of shorebird species have declined globally. After accounting for the influence of traits and species taxonomy, linear mixed-effects models showed that populations of migratory shorebirds decreased more than populations of residents. Besides that, declines were more frequent for species breeding at high latitudes of the Northern Hemisphere, but these patterns did not hold after excluding the non-migratory species. Our findings suggest that factors linked to migration, such as habitat loss as well as deterioration at stop-over or wintering sites and a pronounced climate change impact at high latitudes, are possible drivers of the observed worldwide population decreases.

More Than Just a Trend: Integrating Population Viability Models to Improve Conservation Management of Colonial Waterbirds.

Waterbird populations in eastern Australia have been declining over the past 35 years primarily due to water resource development and resultant changes to natural river flows and flooding. To mitigate these impacts there is an increased allocation of water for the environment, including waterbird populations. We used population viability models to identify the frequency of breeding events required to reverse the trend and achieve long-term species' management objectives. We found that the population size of straw-necked ibis was primarily dictated by the frequency of large breeding events and to a lesser extent by adult annual survival and the frequency of small breeding events. We identified combinations of small and large breeding events over the next 10 years required for increased population growth. We also assessed the likelihood of current water management policies increasing populations and thereby reversing the decline in eastern Australia's waterbird populations.

Response of waterbird abundance and flight behavior to a coastal wind farm on the East Asian-Australasian Flyway.

Coastal wetlands along migratory flyways are crucial in supporting staging or wintering waterbirds, yet they are often targeted for wind energy development. Potential conflicts are likely to be strong in densely populated East and Southeast Asia, where many bird species along the flyway are endangered, and wind energy projects are just flourishing. We investigated waterbird abundance and flight behavior at a coastal wind farm at the mid of the East Asian-Australasian Flyway. For shorebirds roosting in the aquacultural ponds, the abundance showed no significant change in the study area compared with the control area across all development stages of the wind farm. For egrets breeding in the mangroves, fewer Cattle Egrets Bubulcus ibis were observed in the year of wind farm construction and the first year of wind farm operation, then the number recovered afterwards. Since the operation of the wind farm, birds avoided crossing closely spaced (200 m) turbines while travelling through widely spaced (500 m) ones more frequently. Shorebirds, egrets, and landbirds flew lower when turbines were present, reducing the overlap of their flight height with the swept zone. Our study suggests that coastal wind farms are not necessarily a great threat to waterbirds. Yet environmentally sound planning and rigorous monitoring are crucial in minimizing potential impacts.

Parental incubation exchange in a territorial bird species involves sex-specific signalling.

BACKGROUND: Effective communication between sexual partners is essential for successful reproduction. Avian parents with biparental incubation need to know how to negotiate, when and who will incubate, and how to harmonize partner exchange at the nest. Although considerable effort has been dedicated to studies of incubation rhythms, few studies have investigated how behavioural signals serve to tighten cooperation between parents. Moreover, existing studies are almost exclusively restricted to species in which long distances between incubating and non-incubating parents prevent continuous communication during incubation. Thus, the most frequently described parental exchange system is a simple model characterized by the return of the non-incubating parent to the nest itself. Here, we propose more complex parental exchange behaviour in the Northern Lapwing (Vanellus vanellus), a territorial species capable of continuous partner communication during incubation and with a highly variable male contribution to incubation. RESULTS: Northern Lapwing females regularly vocalized shortly before departing from the nest, while males mostly left the nest quietly. Responsiveness of the male to female vocalization, perhaps in combination with her flying away from the nest, helped to synchronize incubation care by increasing the probability of exchange, and also by shortening the exchange gaps. In contrast, a male-to-female exchange gap most often occurred after the male quietly flew away from the nest. The frequency of female vocal signalling was not correlated with the male incubation effort on a between-nest scale, but the highest probability of a female-to-male exchange occurred after vocal signalling by females with the most nest-attentive males. Conversely, lowered effort by females to vocalize in the night was accompanied by lower willingness of males to incubate. CONCLUSIONS: Our results suggest that (1) that the incubating parent can communicate with the non-incubating partner using sex-specific behavioural signals, and this helps to synchronize parental exchange on the nest, (2) this signalling may combine acoustic and visual cues, and (3) the efficiency of this signalling might influence the overall nest attendance. The presumption that the repertoire of behavioural signals during reproduction will be much more complex in territorial species that are capable of continuous communication between the partners during the incubation period should be further tested.

Habitat selection can reduce effects of extreme climatic events in a long-lived shorebird.

Changes in the frequency of extreme climatic events (ECEs) can have profound impacts on individual fitness by degrading habitat quality. Organisms may respond to such changes through habitat selection, favouring those areas less affected by ECEs; however, documenting habitat selection in response to ECEs is difficult in the wild due to the rarity of such events and the long-term biological data required. Sea level rise and changing weather patterns over the past decades have led to an increase in the frequency of coastal flooding events, with serious consequences for ground nesting shorebirds. Shorebirds therefore present a useful natural study system to understand habitat selection as a response to ECEs. We used a 32-year study of the Eurasian oystercatcher (Haematopus ostralegus) to investigate whether habitat selection can lead to an increase in nest elevation and minimize the impacts of coastal flooding. The mean nest elevation of H. ostralegus has increased during the last three decades. We hypothesized that this change has been driven by changes in H. ostralegus territory settlement patterns over time. We compared various possible habitat selection cues to understand what information H. ostralegus might use to inform territory settlement. There was a clear relationship between elevation and territory settlement in H. ostralegus. In early years, settlements were more likely at low elevations but in more recent years the likelihood of settlement was similar between high and low elevation areas. Territory settlement was associated with conspecific fledgling output and conspecific density. Settlement was more likely in areas of high density and areas with high fledgling output. This study shows that habitat selection can minimize the effects of increasingly frequent ECEs. However, it seems unlikely that the changes we observe will fully alleviate the consequences of anthropogenic climate change. Rates of nest elevation increase were insufficient to track current increases in maximum high tide (0.5 vs. 0.8 cm/year). Furthermore, habitat selection cues that rely on information from previous breeding seasons (e.g. conspecific fledgling output) may become ineffective as ECEs become more frequent and environmental predictability is diminished.

Metal and metalloid levels in blood of semipalmated sandpipers (Calidris pusilla) from Brazil, Suriname, and Delaware Bay: Sentinels of exposure to themselves, their prey, and predators that eat them.

Identifying animals as sentinels for humans and other animal species is an excellent method for understanding exposure to environmental contamination at different times and places. Shorebirds are useful sentinels because they have a world-wide distribution, eat a range of prey, and are eaten by a range of other species, including humans. We collected blood from semipalmated sandpipers (Calidris pusilla) wintering in northern (Suriname N = 71) and northeastern (Brazil N = 61) South America to examine levels of heavy metals and metalloids (arsenic, selenium), and compare them to blood levels in sandpipers at a heavily used stopover site in New Jersey (N = 30; Delaware Bay, NJ). Since blood represents relatively recent exposure, it can provide information on where and when the birds were exposed. Levels were highest in Brazil for arsenic and particularly selenium; highest in Suriname for cadmium and lead; and highest in New Jersey for chromium. Samples from Brazil and Suriname presented higher levels of mercury than did those from New Jersey. There were no geographic differences for cobalt. Levels of all metals were generally within an order of magnitude. The significant geographic difference for selenium was interesting because it is regulated in the body. Selenium levels in the NJ sample were directly proportional to levels found in their principle food at this migration stopover site (eggs of horseshoe crab, Limulus polyphemus). Mean selenium level was almost an order of magnitude higher in the semipalmated sandpiper blood samples from Brazil (mean of 27,500 µg/L= ppb) compared to the other sampling locations (mean > 5330 µg/L). This is a toxic level and cause for concern and further investigation, alerting us to look for other evidence of excess selenium exposure. Otherwise the levels of other metals are generally not high enough to cause harm to the sandpipers themselves or to predators that eat them. We discuss the implications for these birds and their exposure to contaminants at different stopover sites.

Rapid climate-driven loss of breeding habitat for Arctic migratory birds.

Millions of birds migrate to and from the Arctic each year, but rapid climate change in the High North could strongly affect where species are able to breed, disrupting migratory connections globally. We modelled the climatically suitable breeding conditions of 24 Arctic specialist shorebirds and projected them to 2070 and to the mid-Holocene climatic optimum, the world's last major warming event ~6000 years ago. We show that climatically suitable breeding conditions could shift, contract and decline over the next 70 years, with 66-83% of species losing the majority of currently suitable area. This exceeds, in rate and magnitude, the impact of the mid-Holocene climatic optimum. Suitable climatic conditions are predicted to decline acutely in the most species rich region, Beringia (western Alaska and eastern Russia), and become concentrated in the Eurasian and Canadian Arctic islands. These predicted spatial shifts of breeding grounds could affect the species composition of the world's major flyways. Encouragingly, protected area coverage of current and future climatically suitable breeding conditions generally meets target levels; however, there is a lack of protected areas within the Canadian Arctic where resource exploitation is a growing threat. Given that already there are rapid declines of many populations of Arctic migratory birds, our results emphasize the urgency of mitigating climate change and protecting Arctic biodiversity.

Why fly the extra mile? Using stress biomarkers to assess wintering habitat quality in migratory shorebirds.

Migratory birds make decisions about how far to travel based on cost-benefit trade-offs. However, in many cases the net effect of these trade-offs is unclear. We sought to address this question by measuring feather corticosterone (CORTf), leucocyte profile, avian malaria parasite prevalence and estimating fueling rates in three spatially segregated wintering populations of the migratory shorebird ruddy turnstone Arenaria interpres during their stay in the winter habitat. These birds fly from the high-Arctic breeding ground to Australia, but differ in that some decide to end their migration early (Broome, Western Australia), whereas others travel further to either South Australia or Tasmania. We hypothesized that the extra costs in birds migrating greater distances and overwintering in colder climates would be offset by benefits when reaching their destination. This would be evidenced by lower stress biomarkers in populations that travel further, owing to the expected benefits of greater resources and improved vitality. We show that avian malaria prevalence and physiological stress levels were lower in birds flying to South Australia and Tasmania than those overwintering in Broome. Furthermore, our modeling predicts that birds in the southernmost locations enjoy higher fueling rates. Our data are consistent with the interpretation that birds occupying more costly wintering locations in terms of higher migratory flight and thermoregulatory costs are compensated by better feeding conditions and lower blood parasite infections, which facilitates timely and speedy migration back to the breeding ground. These data contribute to our understanding of cost-benefit trade-offs in the decision making underlying migratory behaviour.

Thermal emissivity of avian eggshells.

The hypothesis has been tested that evolution has resulted in lower thermal emissivity of eggs of birds breeding openly in cold climates than of eggs of birds that nest under protective covering or in warmer climates. Directional thermal emissivity has been estimated from directional-hemispherical reflectance spectra. Due to several methodological difficulties the absolute emissivity is not accurately determined, but differences between species are obvious. Most notably, small waders of the genus Calidris, breeding in cold climates on the tundra, and in most cases with uniparental nest attendance, have low directional emissivity of their eggshells, about 0.92 when integration is carried out for wavelengths up to 16µm. Species belonging to Galloanserinae have the highest directional emissivity, about 0.96, of their eggs. No differences due to climate or breeding conditions were found within this group. Eggs of most other birds tested possess intermediate emissivity, but the values for Pica pica and Corvus corone cornix are as low as for Calidris. Large species-dependent differences in spectral reflectance were found at specific wavelengths. For instance, at 4.259µm the directional-hemispherical reflectance for galliforms range from 0.05 to 0.09, while for Fratercula arctica and Fulmarus glacialis it is about 0.3. The reflection peaks at 6.5 and 11.3µm due to calcite are differentially attenuated in different species. In conclusion, the hypothesis that evolution has resulted in lower thermal emissivity of bird eggs being exposed in cold climates is not supported by our results. The emissivity is not clearly related to nesting habits or climate, and it is unlikely that the small differences observed are ecologically important. The spectral differences between eggs that nevertheless exist should be taken into account when using infrared thermometers for estimating the surface temperature of avian eggs.

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.

A Bionic Walking Wheel for Enhanced Trafficability in Paddy Fields with Muddy Soil.

To improve wheel trafficability in soft and muddy soils such as paddy fields, a bionic walking wheel is designed based on the structural morphology and movement mode of the feet of waders living in marshes and mudflats, similar to the muddy soil of paddy fields. The bionic walking wheel adopts the arrangement of double-row wheel legs and staggered arrays to imitate the walking posture of waders. The two legs move alternately, cooperate with each other, and improve the smoothness of movement. The cam inside the bionic walking wheel is used to control the movement mode of the feet. The flippers open before touching the ground to increase the contact area and reduce sinking, and the toes bend and grip the ground while touching the ground to increase traction. Multi-rigid-body dynamics software (Adams View 2020) is used to simulate the movement of the wheel during the wading process, and the movement coordination and interference between the wheel legs are analyzed. The simulation results show that there is no interference between the parts and that the movement smoothness is good. The interaction between the bionic walking wheel and muddy soil was analyzed via coupled EDEM-ADAMS simulation, and the simulation analysis and experiments were conducted and compared with those for a common paddy wheel. The results showed that the bionic walking wheel designed in this paper improved the drawbar pull by 113.56% compared with that of a common paddy wheel and had better anti-sinking performance. By analyzing the effect of toe grip on traction, it was found that the soil under the feet can be disturbed to provide greater traction when the toe is bent downward. This study provides a reference for improving the trafficability of walking mechanisms in soft and muddy soils, such as paddy fields.

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.

Trace elements in relation to trophic ecology of long-distance migratory shorebirds and seabirds in West Africa.

Shorebirds and seabirds are abundant predators in coastal habitats worldwide, relying upon a high diversity of benthic invertebrates and fish, respectively. While occupying different trophic guilds, they are differently exposed to element contamination entering the coastal food web. Therefore, these birds have been used as bioindicators of environmental contamination in marine ecosystems. We analysed the concentration of trace elements in blood samples of 16 shorebird and seabird migratory species in a major non-breeding site, the Bijagós Archipelago, in regard to their trophic ecology. Overall, our study shows low exposure of this bird community to toxic elements, except for Hg. Most species presented Hg burdens within the moderate toxicity threshold, but one species (Dunlin) presented values at a potential high Hg toxicity risk. We found a positive relationship between Se and Ni concentrations and δ15N values (a proxy for trophic level). In addition, a positive relationship was found between δ13C (a proxy for habitat characteristics) and Hg, Fe, Cu and Mn, while the opposite pattern was recorded for As. Differences were also shown for several trace elements between the two studied trophic guilds: concentrations of As, Pb and Se were higher in pelagic fish consumers (seabirds), whereas Cr, Fe and Sr burdens were higher in benthic invertebrate consumers (shorebirds). Although previous studies in the same site revealed very high concentrations of Cd and Pb in some of the prey species of shorebirds and seabirds (bivalves and fishes), values found in birds for these two elements suggest no toxicological risk. Thus, exposure to toxic elements is not currently a threat to coastal bird populations, namely those facing apparent local declines in Guinea-Bissau, one of the most important non-breeding quarters for of West Africa. Still, Hg burdens were high in some species, deserving further monitoring.

Site fidelity of migratory shorebirds facing habitat deterioration: insights from satellite tracking and mark-resighting.

BACKGROUND: Site fidelity, the tendency to return to a previously visited site, is commonly observed in migratory birds. This behaviour would be advantageous if birds returning to the same site, benefit from their previous knowledge about local resources. However, when habitat quality declines at a site over time, birds with lower site fidelity might benefit from a tendency to move to sites with better habitats. As a first step towards understanding the influence of site fidelity on how animals cope with habitat deterioration, here we describe site fidelity variation in two species of sympatric migratory shorebirds (Bar-tailed Godwits Limosa lapponica and Great Knots Calidris tenuirostris). Both species are being impacted by the rapid loss and deterioration of intertidal habitats in the Yellow Sea where they fuel up during their annual long-distance migrations. METHODS: Using satellite tracking and mark-resighting data, we measured site fidelity in the non-breeding (austral summer) and migration periods, during which both species live and co-occur in Northwest Australia and the Yellow Sea, respectively. RESULTS: Site fidelity was generally high in both species, with the majority of individuals using only one site during the non-breeding season and revisiting the same sites during migration. Nevertheless, Great Knots did exhibit lower site fidelity than Bar-tailed Godwits in both Northwest Australia and the Yellow Sea across data types. CONCLUSIONS: Great Knots encountered substantial habitat deterioration just before and during our study period but show the same rate of decline in population size and individual survival as the less habitat-impacted Bar-tailed Godwits. This suggests that the lower site fidelity of Great Knots might have helped them to cope with the habitat changes. Future studies on movement patterns and their consequences under different environmental conditions by individuals with different degrees of site fidelity could help broaden our understanding of how species might react to, and recover from, local habitat deterioration.

Translocation of shorebird siblings shows intraspecific variation in migration routines to arise after fledging.

Although many recent tracking studies have uncovered considerable variation in the migratory routines of birds,1,2 the source of this variation is surprisingly poorly discussed.3 We hypothesize that a wealth of possible factors, including factors other than genetics, translate into these variable outcomes. To demonstrate how factors that are not inherited can shape migratory routine during development, we performed a translocation and delayed-release experiment with juvenile, hand-raised black-tailed godwits Limosa limosa limosa that were carefully matched for ancestral background, releasing siblings 1,000 km apart. Translocated juveniles adopted the spatiotemporal pattern of migration that is habitual for the population at the release location rather than the origin. This leads to the rejection of the hypothesis that the migration of inexperienced birds is only shaped by pre-release factors, including genes, maternal material in the eggs, and a common environment from hatching to fledging. Instead, these findings are consistent with inexperienced migrants also developing their knowledge and capacities through contextual individual learning,4 the precise nature of which now warrants study. The fact that hand-raised godwits, depending on the context in which they are released, can be induced to show different migratory routines, wintering sites, and breeding locations from their siblings indicates that processes during development offer the substrate for rapid adaptation of long-distance migration.

A comprehensive comparison of fecal microbiota in three ecological bird groups of raptors, waders, and waterfowl.

Gut microbiota plays a vital role in maintaining the health and immunity of wild birds. However, less is known about the comparison of fecal microbiota between different ecological groups of wild birds, particularly in the Yellow River National Wetland in Baotou, China, an important transit point for birds migrating all over the East Asia-Australian and Central Asian flyways. In this study, we characterized the fecal microbiota and potential microbial function in nine bird species of raptors, waders, and waterfowl using 16S rRNA gene amplicon sequencing to reveal the microbiota differences and interaction patterns. The results indicated that there was no significant difference in α-diversity, but a significant difference in ß-diversity between the three groups of birds. The fecal bacterial microbiota was dominated by Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes in all groups of birds. Furthermore, we identified five bacterial genera that were significantly higher in raptors, five genera that were significantly higher in waders, and two genera that were more abundant in waterfowl. The bacterial co-occurrence network results revealed 15 and 26 key genera in raptors and waterfowls, respectively. The microbial network in waterfowl exhibited a stronger correlation pattern than that in raptors. PICRUSt2 predictions indicated that fecal bacterial function was significantly enriched in the antibiotic biosynthesis pathway in all three groups. Metabolic pathways related to cell motility (bacterial chemotaxis and flagellar assembly) were significantly more abundant in raptors than in waders, whereas waders were enriched in lipid metabolism (synthesis and degradation of ketone bodies and fatty acid biosynthesis). The fecal microbiota in waterfowl harbored more abundant vitamin B6 metabolism, RNA polymerase, and tyrosine and tryptophan biosynthesis. This comparative study revealed the microbial community structure, microbial co-occurrence patterns, and potential functions, providing a better understanding of the ecology and conservation of wild birds. Future studies may focus on unraveling metagenomic functions and dynamics along with the migration routine or different seasons by metagenomics or metatranscriptomics.

Curves for Curlew: Identifying Curlew breeding status from GPS tracking data.

Identifying the breeding status of cryptic bird species has proved problematic without intense or inherently expensive monitoring. Most, if not all, intensive bird monitoring comes with disturbance risks and many projects now rely on tagging of individuals to provide remote information on movements. Given the importance of breeding status when targeting conservation interventions novel methods are needed. This study aimed to identify breeding status in Eurasian Curlew (Numenius arquata) from GPS tag movement patterns using the "recurse" package in R. This package identifies foci of activity (using K-means clustering) based on revisitations. Using a training data set from an individual of known breeding status, we visually assessed the frequency of revisits to particular locations to identify prebreeding, incubation, chick guarding, and post-breeding stages to an accuracy of a within at most half a day and thus breeding outcomes. Limited validation was provided by additional field observations. Based on our results, we estimate a low daily nest survival rate of 0.935 during incubation, that only a small proportion of individuals successfully raised young, and that there was a high proportion (26%) of non-breeders in the population. The Eurasian Curlew is a species of high conservation concern across Europe, and our results concur with recent studies highlighting that population declines are likely to be driven by low levels of productivity. The acquisition of improved knowledge on the behaviors of individuals at each stage of breeding enables more targeted conservation efforts and reduces the need for additional monitoring visits that may cause increased disturbance and risk of nest failure. We hope that the approach outlined may be developed to provide practitioners who have detailed knowledge of the behavior of their study species with a practical means of assessing the breeding status and outcomes of their study populations.

Unmanned Aircraft Systems as a Powerful Tool to Detect Fine-Scale Spatial Positioning and Interactions between Waterbirds at High-Tide Roosts.

The surveillance of behavioral interactions between individuals in bird populations is important to understand social dynamics and explain distribution patterns caused by competition for food and space. For waterbirds, little is known about interactions between individuals at high-tide roosts. In the present study, we used surveying with unmanned aircraft systems (UASs) to provide enhanced information on previously hidden aspects of the highly dynamic communities of roosting waterbirds in the non-breeding season. Fine-scale density estimations, derived from aerial photos obtained with UASs, were used as a measure to explain intra- and inter-species interactions for 10 selected waterbird species on a major roost site in the Danish Wadden Sea. Uniquely defined density distributions were detected, which, to some degree, were dependent on species and species size, with smaller waders exhibiting densely packed flocks (e.g., dunlin Calidris alpina and golden plover Pluvialis apricaria), whereas larger species, such as ducks and geese (Anatidae) exhibited lower densities. Multi-species flocks were observed to occur frequently (31.9%) and generally resulted in lower densities than single-species flocks for each of the species involved. Furthermore, it has been demonstrated that UAS aerial photos can be used both to assess positions for roosting waterbirds and to classify habitats (i.e., mudflats, vegetated areas, waterline, and flooded areas) during high-tide. This facilitated the collection of precise data for temporal habitat choices for individual species when using the studied roost site. Our study highlights UAS surveys as an effective tool to gather hitherto unobtainable data for individual occurrences of roosting waterbirds on a spatiotemporal scale.