Functional reorganization of North American wintering avifauna.

Wintering birds serve as vital climate sentinels, yet they are often overlooked in studies of avian diversity change. Here, we provide a continental-scale characterization of change in multifaceted wintering avifauna and examine the effects of climate change on these dynamics. We reveal a strong functional reorganization of wintering bird communities marked by a north-south gradient in functional diversity change, along with a superimposed mild east-west gradient in trait composition change. Assemblages in the northern United States saw contractions of the functional space and increases in functional evenness and originality, while the southern United States saw smaller contractions of the functional space and stasis in evenness and originality. Shifts in functional diversity were underlined by significant reshuffling in trait composition, particularly pronounced in the western and northern United States. Finally, we find strong contributions of climate change to this functional reorganization, underscoring the importance of wintering birds in tracking climate change impacts on biodiversity.

Gut fungi of black-necked cranes (Grus nigricollis) respond to dietary changes during wintering.

BACKGROUND: Migratory birds exhibit heterogeneity in foraging strategies during wintering to cope with environmental and migratory pressures, and gut bacteria respond to changes in host diet. However, less is known about the dynamics of diet and gut fungi during the wintering period in black-necked cranes (Grus nigricollis). RESULTS: In this work, we performed amplicon sequencing of the trnL-P6 loop and ITS1 regions to characterize the dietary composition and gut fungal composition of black-necked cranes during wintering. Results indicated that during the wintering period, the plant-based diet of black-necked cranes mainly consisted of families Poaceae, Solanaceae, and Polygonaceae. Among them, the abundance of Solanaceae, Polygonaceae, Fabaceae, and Caryophyllaceae was significantly higher in the late wintering period, which also led to a more even consumption of various food types by black-necked cranes during this period. The diversity of gut fungal communities and the abundance of core fungi were more conserved during the wintering period, primarily dominated by Ascomycota and Basidiomycota. LEfSe analysis (P < 0.05, LDA > 2) found that Pyxidiophora, Pseudopeziza, Sporormiella, Geotrichum, and Papiliotrema were significantly enriched in early winter, Ramularia and Dendryphion were significantly enriched in mid-winter, Barnettozyma was significantly abundant in late winter, and Pleuroascus was significantly abundant in late winter. Finally, mantel test revealed a significant correlation between winter diet and gut fungal. CONCLUSIONS: This study revealed the dynamic changes in the food composition and gut fungal community of black-necked cranes during wintering in Dashanbao. In the late wintering period, their response to environmental and migratory pressures was to broaden their diet, increase the intake of non-preferred foods, and promote a more balanced consumption ratio of various foods. Balanced food composition played an important role in stabilizing the structure of the gut fungal community. While gut fungal effectively enhanced the host's food utilization rate, they may also faced potential risks of introducing pathogenic fungi. Additionally, we recongnized the limitations of fecal testing in studying the composition of animal gut fungal, as it cannot effectively distinguished between fungal taxa from food or soil inadvertently ingested and intestines. Future research on functions such as cultivation and metagenomics may further elucidate the role of fungi in the gut ecosystem.

Relationship between wintering site and survival in a migratory waterbird using different migration routes.

When wintering at different sites, individuals from the same breeding population can experience different conditions, with costs and benefits that may have implications throughout their lifetime. Using a dataset from a longitudinal study on Eurasian Spoonbills from southern France, we explored whether survival rate varied among individuals using different wintering sites. In the last 13 years, more than 3000 spoonbills have been ringed as chicks in Camargue. These birds winter in five main regions that vary in both migratory flyway (East Atlantic vs. Central European) and migration distance (long-distance vs. short-distance vs. resident). We applied Cormack-Jolly-Seber models and found evidence for apparent survival to correlate with migration distance, but not with flyway. During the interval between the first winter sighting and the next breeding period, long-distance migrants had the lowest survival, independently of the flyway taken. Additionally, as they age, spoonbills seem to better cope with migratory challenges and wintering conditions as no differences in apparent survival among wintering strategies were detected during subsequent years. As dispersal to other breeding colonies was rarely observed, the lower apparent survival during this period is likely to be partly driven by lower true survival. This supports the potential role of crossing of natural barriers and degradation of wintering sites in causing higher mortality rates as recorded for a variety of long-distance migrants. Our work confirms variation in demographic parameters across winter distribution ranges and reinforces the importance of longitudinal studies to better understand the complex demographics of migratory species.

Methylmercury exposure and risk of wintering migratory birds in the Poyang Lake basin, China.

Mercury (Hg), especially methylmercury (MeHg), is a pervasive contaminant that poses significant risks to birds occupying high trophic levels. However, we have little knowledge about the mercury exposure and its risks for birds in Poyang Lake basin, China. Therefore, during 2020-2021, we investigated MeHg concentrations in breast feathers of wintering migratory birds (n = 430 from 43 species belonging to 9 orders) in Poyang Lake Nanji Wetland and Jiangxi Nanfengmian National Nature Reserve, China. MeHg concentrations in breast feathers varied greatly by species, foraging guilds and taxonomic orders, among which the highest concentration was detected in great egret (8849 ± 5975 ng g-1 dw). Comparing with studies worldwide, high MeHg concentrations in feathers of Ardeidae from Pelecaniformes were found in this area. Moreover, herons migrating between northern and southern China had lower MeHg concentration than residents in southern China related to habitat Hg. Considering the applicability and sensitivity of the equations for the transformation of MeHg concentrations in feathers to blood-equivalent total Hg (THg) values, method CJ that the equation based on songbirds was used for the transformation of the songbirds and the equation based on seabirds for the others performed better than other three for risk assessment of bird Hg in this study. 23.1% of birds from Poyang Lake were at risk of Hg exposure based on the method CJ. Carnivorous birds from Pelecaniformes had the highest risk levels, with 37.2% categorized as no risk (≤200 ng g-1 ww), 48.9% as low risk (200-1000 ng g-1 ww), 11.1% as moderate risk (1000-3000 ng g-1 ww), 1.1% as high risk (3000-4000 ng g-1 ww), and 1.7% as severe risk (>4000 ng g-1 ww). These risks suggest long-term monitoring and further advanced studies about freshwater waterbirds Hg exposure is necessary.

Effects of 2 wintering practices on behavioral and physiological indicators of welfare of nonlactating, pregnant dairy cattle in a pasture-based system.

In countries with pasture-based dairy systems and relatively cold winters, such as New Zealand, it is common to manage pregnant, nonlactating cows on forage crop paddocks rather than pasture, due to slow pasture growth rates. Wintering dairy cattle on grazed crops can compromise welfare if wet and muddy underfoot conditions occur, which can reduce lying. This study investigated behavioral and physiological indicators of welfare of cows under 2 wintering practices: cows managed on and grazed kale crop (Brassica oleracea), and cows managed on pasture with baled hay. Following dry-off (d 0), 80 cows were randomly assigned to 1 of the 2 wintering practices (40 cows/practice) and monitored between d 4 and 32 (phase 1). During this period, lying and stepping behavior was continuously recorded using leg-based accelerometers. Blood samples were obtained at d 0 and 32 for measurements of thyroxine (T4), nonesterified fatty acids (NEFA), white blood cells (WBC), and red blood cells. All data for phase 1 were presented descriptively due to the lack of treatment replication. Daily mean air temperature during this period was 5.2°C (range: 0.0-10.7°C), and rainfall was 1.1 mm/d (range: 0-5.6mm/d). Between d 4 and 32, cows in both groups spent similar amounts of time lying (pasture with hay cows: 8.9 h/24 h ± 2.57, kale crop cows: 8.7 h/24 h ± 3.06, mean ± SEM). Both groups reduced their lying on wet and cold days, and there was evidence of rebound lying once unfavorable weather conditions stopped. Cows on kale crop had numerically higher NEFA and lower WBC compared with cows managed on pasture, although most physiological values were within normal ranges. In a second phase of the study (d 34 and 35), cows were managed under controlled, replicated conditions in the 2 wintering practices using typical on-farm stocking rates (2 or 4 cows per group in the pasture with hay and kale crop treatments, respectively; n = 10 groups/treatment). During this period, cow behavior, skin and surface temperatures, hygiene scores, feed intakes, and ground conditions were measured. Weather conditions during the 48-h exposure were mostly cold and dry (mean air temperature: 7.8°C, range: -2.2 to 20.5°C). Cows managed on pasture with hay spent more time lying down on the first day of exposure; however, this was likely due to less space being available to kale cows on this day. Cows managed on pasture with hay ruminated more than cows on kale crop on both days of observations (d 1: 37.9% vs. 30.9% of observations, d 2: 36.8% vs. 28.7% of observations for pasture with hay and kale crop groups, respectively) and were lying more often in postures indicative of greater thermal comfort. Cows managed on pasture with hay had higher skin and surface temperatures compared with cows on kale crop, whereas cows on kale crop had dirtier coats. Results suggest that opportunities for thermal comfort were greater for cows managed on pasture with hay bales, which may be due to increased rumination activities and more insulated lying areas.

Timing mowing for maximal energy gain - Managing foraging habitat of wintering geese under extreme drought conditions.

The availability of high-quality food resources is a critical determinant of wildlife fitness. Over the past two decades, phenological mismatch - the temporal misalignment between animals' peak nutrient demand and optimal resource availability - has emerged as a significant conservation challenge. This issue is particularly worrisome for migratory birds, which must accumulate energy reserves to meet the elevated metabolic demands of migration between breeding and wintering grounds. In Poyang Lake, a crucial wintering ground along the East Asian-Australasian flyway, increasing asynchrony between vegetation growth and the migration of herbivorous waterbirds significantly impedes conservation efforts and presents a major management challenge for this Ramsar wetland. This study evaluates the efficacy of mowing, a grassland management measure, in regulating plant growth processes and restoring food resources for geese. In-situ mowing experiments were conducted with varying timings in Carex wet meadows, the primary foraging habitats of geese. Optimal mowing times were identified, and the maximum goose carrying capacity was assessed by comparing Carex growth and nutritional dynamics with goose dietary requirements. The results reveal that mowing effectively slows down the aging process of Carex, and protein content is identified as a critical limiting factor for geese foraging. Different mowing timings extend the suitable foraging period by 11-25 days. Estimates suggest varying carrying capacities with different mowing timings, supporting goose populations ranging from 133 to 2,046 in Changhuchi Lake during wintering. The optimal mowing window is early October, avoiding dates before late September and after late November. Moreover, multiple-stage mowing is recommended to accommodate different wintering stages. The study highlights mowing as a potential habitat restoration approach for goose conservation, effectively mitigating the challenges imposed by phenological mismatch directly and indirectly caused by anthropogenic activities.

Temperature-Caused Changes in Raman Pattern and Protein Profiles of Winter Triticale (x Triticosecale, Wittm.) Field-Grown Seedlings.

Climate change, which causes periods with relatively high temperatures in winter in Poland, can lead to a shortening or interruption of the cold hardening of crops. Previous research indicates that cold acclimation is of key importance in the process of acquiring cereal tolerance to stress factors. The objective of this work was to verify the hypothesis that both natural temperature fluctuations and the plant genotype influence the content of metabolites as well as proteins, including antioxidant enzymes and photosystem proteins. The research material involved four winter triticale genotypes, differing in their tolerance to stress under controlled conditions. The values of chlorophyll a fluorescence parameters and antioxidant activity were measured in their seedlings. Subsequently, the contribution of selected proteins was verified using specific antibodies. In parallel, the profiling of the contents of chlorophylls, carotenoids, phenolic compounds, and proteins was carried out by Raman spectroscopy. The obtained results indicate that a better PSII performance along with a higher photosystem II proteins content and thioredoxin reductase abundance were accompanied by a higher antioxidant activity in the field-grown triticale seedlings. The Raman studies showed that the cold hardening led to a variation in photosynthetic dyes and an increase in the phenolic to carotenoids ratio in all DH lines.

Temporal and interspecific dietary variation in wintering ducks in agricultural landscapes.

Farmlands are becoming more important as waterfowl foraging habitats, while natural wetlands are being lost globally. However, it is unclear how waterfowl coexist in agricultural landscapes by resource partitioning. We evaluated the diets of seven sympatric dabbling ducks foraging in rice paddy and lotus fields around Lake Kasumigaura, the second largest lake in Japan, during two wintering seasons (from November to February) by faecal DNA metabarcoding using chloroplast trnL and mitochondrial CO1 region sequences. We examined 420 faecal samples and found different patterns of dietary diversity and composition among the duck species. The pattern also differed between plant and invertebrate food. Dietary niche partitioning was clear in plant food. Large-bodied ducks intensively use crop plants, and other ducks might mediate competition by using terrestrial and aquatic plants that are suitable for their foraging behaviours or microhabitats. Dietary segregation among species was the most apparent in February, when the abundance of foraging ducks was the largest. This study illustrated the complex pattern of dietary niche partitioning of dabbling ducks in agricultural landscapes, which might be difficult to evaluate by conventional approaches. The availability of crop plants, as well as other plant food resources in flooted areas and farmland dikes, may enable ducks to coexist by spatial or behavioural resource partitioning.

An improved comprehensive model for assessing the heavy metals exposure towards waterbirds: A case report from Black-necked cranes (Grus nigricollis) in Caohai Wetland, China.

Heavy metal contamination poses a significant environmental threat to wildlife on global scale, making accurate assessment of exposure risk crucial for conservation efforts, particularly for vulnerable species. Existing risk assessment models have been widely used, but their construction process lacks comprehensive considerations. In this study, we constructed an optimized health risk assessment model based on the well-established "Liu's model" and "ADI model", and applied the pollution allocation factor (AF) to accurately assess the risk of heavy metal exposure to wildlife. Our model was applied to assess exposure risk of heavy metal for the black-necked crane(Grus nigricollis), a flagship species in the alpine wetland ecosystem of Caohai Wetland. Soil, plant and black-necked crane fecal samples were collected from the Caohai Wetland and surrounding areas in Guizhou, China. We revealed varying degrees of As, Cd, Cr, Ni, Pb, and Zn contamination in soil and plants from different habitats, exceeding the background or plant limit values. This indicated that the black-necked crane and other waterbirds living in Caohai Wetland are suffering with the multi-elemental heavy metal contamination, especially in the gutterway and grassland. The exposure dose of As, Cd, Cr, Ni, Cu, and Zn toward black-necked cranes differed significantly in soil and plant pathways (P < 0.05). As, Cd, Cu, and Zn were mainly derived from plants consumption, while Cr and Ni originated from soil. Considering the contribution of soil and plant pathways to heavy metal exposure in black-necked cranes, the exposure doses of each elements calculated via food intake accounted for over half of the exposure calculated via feces (AF>0.5). The risk assessment model identified Cr and Pb were the highest risk elements for black-necked cranes, with exposure risk simulated through feces exceeding those through food. These findings suggested that current Liu's model may underestimate the effects of other pathways and medium. Therefore, we proposed a more comprehensive and accurate model for evaluating the exposure risk of black-necked cranes, incorporating AF to quantify the contribution of risk sources to black-necked cranes and understand their overall health risk. This model can serve as a useful tool for the conservation and habitat quality improvement of the black-necked cranes and other waterbirds.

Molecular Changes in the Brain of the Wintering Calidris pusilla in the Mangroves of the Amazon River Estuary.

Migrant birds prepare differently to fly north for breeding in the spring and for the flight to lower latitudes during autumn, avoiding the cold and food shortages of the Northern Hemisphere's harsh winter. The molecular events associated with these fundamental stages in the life history of migrants include the differential gene expression in different tissues. Semipalmated sandpipers (Calidris pusilla) are Arctic-breeding shorebirds that migrate to the coast of South America during the non-breeding season. In a previous study, we demonstrated that between the beginning and the end of the wintering period, substantial glial changes and neurogenesis occur in the brain of C. pusilla. These changes follow the epic journey of the autumn migration when a 5-day non-stop transatlantic flight towards the coast of South America and the subsequent preparation for the long-distance flight of the spring migration takes place. Here, we tested the hypothesis that the differential gene expressions observed in the brains of individuals captured in the autumn and spring windows are consistent with the previously described cellular changes. We searched for differential gene expressions in the brain of the semipalmated sandpiper, of recently arrived birds (RA) from the autumnal migration, and that of individuals in the premigratory period (PM) in the spring. All individuals were collected in the tropical coastal of northern Brazil in the mangrove region of the Amazon River estuary. We generated a de novo neurotranscriptome for C. pusilla individuals and compared the gene expressions across libraries. To that end, we mapped an RNA-Seq that reads to the C. pusilla neurotranscriptome in four brain samples of each group and found that the differential gene expressions in newly arrived and premigratory birds were related with neurogenesis, metabolic pathways (ketone body biosynthetic and the catabolic and lipid biosynthetic processes), and glial changes (astrocyte-dopaminergic neuron signaling, astrocyte differentiation, astrocyte cell migration, and astrocyte activation involved in immune response), as well as genes related to the immune response to virus infections (Type I Interferons), inflammatory cytokines (IL-6, IL-1ß, TNF, and NF-κB), NLRP3 inflammasome, anti-inflammatory cytokines (IL-10), and cell death pathways (pyroptosis- and caspase-related changes).

Waterfowl Wintering in Cities of Temperate Climatic Zone and Its Shaping Factors.

The dynamics of the population size and species diversity of wintering waterfowl was for the first time studied in 30 cities of Russia over eight years. The total population size increased by 35%. The species diversity was found to reach 32 species in total. The mallard Anas platyrhynchos dominated in all 30 cities. The cities grouped to form seven clusters significantly differing from each other by the total parameter set. The geographical location and climatic characteristics of a city are the main environmental conditions for both people and birds. The variance of the wintering waterfowl population size was determined to the extent of 93% by the area and human population size of the city; and 62% of the variance in species number was determined by the longitude, the average January temperature, and the human population size of the city (p < 0.001). The population size and species number of birds correlated with the "age" of the wintering place (p < 0.05). If the urbanization rate continues the same, the population size and species diversity are expected to grow further.

Community modeling reveals the importance of elevation and land cover in shaping migratory bird abundance in the Andes.

The tropical Andes are characterized by extreme topographic and climatic complexity, which has likely contributed to their outstanding current species diversity, composed of many range-restricted species. However, little is known about how the distribution and abundance of highly mobile organisms, like long-distance migratory birds, varies across different land covers, elevations, and climatic conditions within the Andes. We conducted 1,606 distance-sampling point counts across the Colombian Andes, spanning elevations from 253 to 3,708 m, a range of precipitation regimes and representative land covers. We then employed a novel application of a multispecies hierarchical modeling approach to evaluate how elevation, local land cover, aboveground woody biomass, cloud cover, precipitation, and seasonality in precipitation shape the abundance of the migratory land bird community in the Andes. We detected 1,824 individuals of 29 species of migratory land birds, six of which were considered incidental in our study region. We modeled the abundance of the remaining 23 species, while considering observer and time of day effects on detectability. We found that both elevation and land cover had an overriding influence on the abundance of migratory species across the Andes, with strong evidence for a mid-elevation peak in abundance, and species-specific responses to both variables. As a community, migratory birds had the highest mean abundance in shade coffee plantations, secondary forest, and mature forest. Aboveground woody biomass did not affect the abundance of all species as a group, but a few showed strong responses to this variable. Contrary to predictions of a positive correlation between abundance and precipitation, we found no evidence for community-level responses to precipitation, aside for a weak tendency for birds to select areas with intermediate levels of precipitation. This novel use of a multispecies model sheds new light on the mechanisms shaping the winter distribution of migratory birds and highlights the importance of elevation and land cover types over climatic variables in the context of the Colombian Andes.

Should I stay or should I fly? Migration phenology, individual-based migration decision and seasonal changes in foraging behaviour of Common Woodpigeons.

Migration is used by many species as a strategy to deal with a seasonally changing environment. For some species, migration patterns can vary across different or even within the same breeding area. The Common Woodpigeon Columba palumbus, an abundant and widespread Palearctic species, exhibits three migratory strategies (strictly migratory, partially migratory and resident) across its European breeding grounds. Based on ring recoveries and satellite tracking data, we investigated the migration and foraging behaviour of Woodpigeons breeding in Southwestern Europe (Portugal) and Central Europe (Germany). We found that individuals could be classified as residents (Portugal) or partial migrants (Germany), with migrating individuals following the European sector of the East Atlantic flyway, and mainly wintering in France. In addition to general data on migration phenology, we provide evidence for different migration strategies (migration of varying distances or resident behaviour), low wintering site fidelity and the use of multiple wintering sites. Furthermore, tracking data provided information on migratory behaviour in consecutive years, clearly showing that individuals may switch migratory strategies (resident vs. migrant) between years, i.e. are facultative partial migrants. While individuals from Portugal mainly stayed within a large park ('green urban area') year-round, Woodpigeons from the city of Giessen (Germany) regularly left the urban area to forage on surrounding farmland (with an average distance covered of 5.7 km), particularly from July to September. Overall, our results highlight the behavioural plasticity in Woodpigeons in terms of foraging and migration strategies within and amongst individuals as well as populations.

Prehatching temperatures drive inter-annual cohort differences in great tit metabolism.

Basal metabolic rate (BMR) constitutes the lowest metabolic rate in a resting animal and is, therefore, considered to reflect the energetic cost of maintenance in endotherms. BMR is a reversible plastic trait that changes with environmental and ecological circumstances, albeit being heritable and susceptible to selection. Inter-individual variation within populations of small birds is substantial, and while many of the drivers of such variation have been identified, many remain unexplained. We studied winter BMR variation of juveniles over a 15-year period in a wild population of great tits Parus major at the northern border of their distribution. BMR during winter consistently changed between years, even after controlling for environmental factors, suggestive of a non-reversible developmental plasticity shaping the adult metabolic phenotype. BMR in cohorts of wintering great tits varied among winters as a response to minimum ambient temperatures experienced early in life, during the prehatching period. This developmental plasticity might be adaptive if temperatures experienced by growing embryos would metabolically prime them to an environment that they will likely encounter in future life. However, in line with a more unpredictable future climate, the risk of phenotype-environment mismatch is likely to lead to certain cohorts being poorly adapted to prevailing winter conditions, resulting in wider annual fluctuations in population size.

Plasticity in the hippocampal formation of shorebirds during the wintering period: Stereological analysis of parvalbumin neurons in Actitis macularius.

The number of parvalbumin neurons can be modified by social, multisensory, and cognitive stimuli in both mammals and birds, but nothing is known about their plasticity in long-distance migratory shorebirds. Here, in the spotted sandpiper (Actitis macularius), we investigated the plasticity of parvalbumin neurons of two brain areas during this species' wintering period at a lower latitude. We compared individuals in a nonmigratory rest period (November-January) and premigration (May-July) period. We used parvalbumin as a marker for counting a subpopulation of inhibitory neurons in the hippocampal formation (HF), with the magnocellular nucleus of the tectal isthmus (IMC) as a control area. Because the HF is involved in learning and memory and social interaction and the IMC is essential for control of head, neck, and eye movements, we hypothesized that parvalbumin neurons would increase in the HF and remain unchanged in the IMC. We used an optical fractionator to estimate cell numbers. Compared with the nonmigratory rest birds, parvalbumin neuron count estimates in the premigration birds increased significantly in the HF but remained unchanged in IMC. We suggest that the greater number of parvalbuminergic neurons in the HF of A. macularius in the premigration period represents adaptive circuitry changes involved in the migration back to reproductive niches in the northern hemisphere.

Variable tropical moisture and food availability underlie mixed winter space-use strategies in a migratory songbird.

Identifying environmental correlates driving space-use strategies can be critical for predicting population dynamics; however, such information can be difficult to attain for small mobile species such as migratory songbirds. We combined radio-telemetry and high-resolution GPS tracking to examine space-use strategies under different moisture gradients for wood thrush (Hylocichla mustelina). We explored the role moisture plays in driving food abundance and, in turn, space-use strategies at a wintering site in Belize across 3 years. Individuals occupying drier habitats experienced lower food abundance and poorer body condition. Using data from our radio-tracked study population and GPS tracking from across five breeding populations, we detected low rates of overwinter site persistence across the wood thrush wintering range. Contrary to expectations, individuals in wetter habitats were more likely to engage in permanent mid-winter relocations, up to 148 km. We suggest facultative movements are instead a condition-dependent strategy that enables wintering wood thrush to locate alternative habitat as food availability declines throughout the dry season. Increased aridity is predicted across the wintering range of wood thrush, and future research should delve deeper into understanding how moisture impacts within and between season space-use dynamics and its ultimate impact on the population dynamics of this declining species.

Structural changes in the gut microbiota community of the black-necked crane (Grus nigricollis) in the wintering period.

During overwintering of black-necked cranes (Grus nigricollis), the composition and function of the gut microbiota changes are of considerable interest for understanding its environmental adaption mechanism. In this study, we characterized the structure of the gut microbiota from the black-necked crane in the Dashanbao wintering area, and compared the early-winter (November) microbiota to the late-winter (March of the next year) microbiota. The results showed that the gut microbiota diversity of black-necked crane in the early-overwintering stage was higher than that in the late-overwintering stage, but it did not reach a significant level. Gut microbiota taxonomic composition analysis showed that relative abundance of Bacteroidota increased significantly, and showed decreased Firmicutes to Bacteroidota ratio at the phylum level, meanwhile, the abundance of Lactobacillus decreased significantly at the genus level. Explain gut microbiota between the early- and late-wintering showed some differences in microbiota richness but maintained a relatively conservative microbiota structure. PICRUSt2 method was used to predict and analyze the KEGG functional abundance of 16S rDNA sequences of bacteria, it was found that the changes in gut microbiota composition increased the abundance of bacteria associated with amino acid biosynthesis and acid metabolism in the late stage of overwintering. This work provides basic data for black-necked crane gut microbiota study, which might further contribute to their protection.

Multi-species prey dynamics influence local survival in resident and wintering generalist predators.

Stochasticity in food availability influences vital rates such as survival and fertility. Life-history theory predicts that in long-lived organisms, survival should be buffered against environmental stochasticity showing little temporal variability. Furthermore, to optimize survival prospects, many animal species perform migrations to wintering areas where food availability is larger. Species with large latitudinal distribution ranges may show populations that migrate and others that are resident, and they may co-occur in winter. One example of these species is the predatory raptor buzzard Buteo buteo. Here, we test whether temporal variability in the density of five small mammal species of prey inhabiting different habitats (shrubland and forests) influences local annual survival of buzzards in a wintering area depending on their age and residency status (residents versus wintering individuals). We found that prey density explained a considerable amount of annual changes in local survival, which was higher for older and resident birds. This difference in local survival likely corresponded to philopatry to the wintering area, which was larger for residents and increased when prey density was larger. The total density of prey inhabiting open shrublands was the variable explaining more variance in temporal variability of local survival, even though the study area is mostly occupied by woodlands. Temporal population dynamics of the different small mammals inhabiting shrublands were not synchronous, which suggests that buzzards preyed opportunistically on the most abundant prey each winter. Generalist predation may buffer the impact of resource unpredictability for pulsed and asynchronous prey dynamics, typical of small mammals in winter.

Characterization of the gut microbiome of black-necked cranes (Grus nigricollis) in six wintering areas in China.

The black-necked crane (Grus nigricollis) is a vulnerable species, breeding exclusively on the high-altitude wetlands of the Qinghai-Tibet Plateau. Bird species harbor diverse communities of microorganisms within their gastrointestinal tracts, which have important roles in the health, nutrition, and physiology of birds. Hitherto, virtually nothing was known about the gut microbial communities associated with wild black-necked cranes. For the first time, this study characterized the gut microbial community compositions, diversity, and functions of black-necked cranes from six wintering areas in China using the Illumina Miseq platform. The taxonomic results revealed that Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes were the four most abundant phyla in the gut of black-necked cranes. At the genus level, 11 genera including Lactobacillus, Pseudomonas, Carnobacterium, Pantoea, Enterococcus, Erwinia, Turicibacter, Bacillus, Phenylobacterium, Sanguibacter, and Psychrobacter were dominant. The differences in the gut microbial community alpha and the beta diversities of black-necked cranes among the six wintering areas were investigated. Furthermore, the representative microbial taxa and their predicted functions in each wintering location were also determined. These data represent the first analysis of the gut microbiome of black-necked cranes, providing a baseline for further microbiological studies and a foundation for the conservation of this bird.

Generational shift in the migratory common noctule bat: first-year males lead the way to hibernacula at higher latitudes.

Many migratory species have shifted their geographic distribution in response to climate change, yet the underlying mechanisms are poorly understood, particularly for mammals. We hypothesized that generational shifts are underlying the observed colonization of hibernation sites further north in a migratory bat, the common noctule (Nyctalus noctula). To evaluate our hypothesis, we collected long-term data on the migratory status and demography of common noctules in a recently colonized hibernation area. Based on isotopic data of 413 individuals, we observed a significant decline in the proportion of long-distance migrants from 2004 to 2015 for both sexes and across all age groups. Demographic data collected between 2007 and 2016 from 3394 individuals demonstrated that subadult males were more abundant during the early colonization stage, followed by a gradual shift to a more balanced age and sex composition. Our results suggest that the colonization of hibernacula at higher latitudes is promoted by generational shifts, involving mostly first-year males. Generational shifts seem to be a likely mechanism for distribution changes in other bats and potentially also in other mammals.