Avian embryos, which develop within eggs, exhibit remarkable tolerance to extremely low temperatures. Despite being a common trait among all birds, the mechanisms underlying this cold tolerance in avian embryos remain largely unknown. To gain a better understanding of this phenomenon and the coping mechanisms involved, we reviewed the literature on severe cold tolerance in embryos of both wild and domestic birds. We found that embryos of different bird orders exhibit tolerance to severe cold during their development. In response to cold stress, embryos slow down their heartbeat rates and metabolism. In severe cold temperatures, embryos can suspend these processes, entering a torpid-like state of cardiac arrest. To compensate for these developmental delays, embryos extend their regular incubation periods. Depending on their embryonic age, embryos of all bird species can tolerate acute severe cold regimes; only a few tolerate chronic severe cold regimes. We also discussed various extrinsic and intrinsic factors that affect the tolerance of bird embryos to low temperatures before and after incubation. Cold tolerance appears to be a heritable trait shared by wild and domestic embryos of all bird classes, regardless of egg size or development (altricial/precocial). Driven by environmental variability, cold tolerance in avian embryos is an optimal physiological and ecological strategy to mitigate the adverse effects of cold conditions on their development in response to fluctuating environmental temperatures.

With the continued development of tracking technology and increasing interest in animal movement, our understanding of migration behavior has become more comprehensive. However, there are still many species that have not been well studied, particularly sea birds. Here, we present the first year-round Global Positioning System (GPS) tracking data of the Black-tailed Gull (Larus crassirostris) at the population level. We used solar-powered GPS-Global System for Mobile communication (GSM) loggers to successfully track 30 individuals breeding at Xingrentuo Islet, Liaoning Province, China, for 1–3 years. Except for one individual who roamed in the far north of the Yellow Sea during non-breeding period, all others did a directed southward migration. Migration routes and wintering sites differed among migrating gulls and between years for the birds tracked for two or more years. Additionally, during wintering, the migrating gulls were more likely to travel over a large body of water and shift sites, and some trajectories were quite complex, which was probably closely related to what we observed in the field about their boat-chasing behavior. Compared to wintering movements, the post-breeding movements ranged over a smaller area. Specifically, almost all of them had a long post-breeding period near the breeding islet (≥120 days, <220 ​km from the breeding islet), and 80% of the gulls who were tracked more than one year had at least one faithful post-breeding site. Compared to the post-breeding period, only approximately half of the migrating gulls had a pre-breeding period that was shorter (3–20 days) and closer to the breeding islet (≤80 ​km). Migration distance varied among migrating gulls (range 209–2405 ​km) and the gulls moved least distance during post-breeding period. Furthermore, we found that the southward movement of the migrating gulls occurred when the temperature near the breeding islet dropped; specifically, the gulls directly migrated southward away from the post-breeding site. Our results suggest that the Black-tailed Gull has a long post-breeding period but a short pre-breeding period near the breeding islet and high diversity of their migrating patterns (in especial migration routes and wintering sites).

The hydrological regime in wetlands plays an important role in the process of wintering waterbird metacommunity assemblage. However, increasing frequency of extreme climate and the intensification of human activities, such as the construction of sluices and dams, have resulted in frequently abnormal hydrological regime in the middle and lower Yangtze River floodplain. In recent years, earlier flood recession has become one of the main hydrological problems faced in the shallow lakes, having a great impact on wetland biodiversity. It is necessary to understand the impact of earlier flood recession on waterbirds, an indicator of wetland biodiversity, and the metacommunity concept is helpful to elucidate the underlying mechanism involved in the processes of assemblage by waterbird communities. In this study, we surveyed the wintering waterbirds at three sub-lakes of Caizi Lakes during 2019–2020 and 2020–2021 and compared the richness, abundance, alpha and beta diversity of waterbirds in and among local metacommunities under earlier flood recession and normal hydrological regime. The results showed that the earlier flood recession reduced the species richness in the early stage and abundance in the late stage, it also reduced the Shannon–Wiener index in the early stage and increased the dissimilarity between and within waterbird metacommunities in the late stage. The partition of beta diversity showed that the turnover component played a major role in the process of waterbird metacommunity assemblage. It was found that the earlier flood recession reduced the richness, abundance in different stages of flood recession, which also increased the turnover of waterbirds. Metacommunities with high habitat heterogeneity had better resistance to abnormal hydrological regime, which resulted in high dissimilarity between and within metacommunities. The results of this study provide important information for waterbird conservation and water level management at shallow lakes in the middle and lower Yangtze River floodplain.

Artificial nest boxes are placed to attract birds to nest and breed in a specific location, and they are widely used in avian ecology research and in the attraction of insectivorous birds. There is evidence that artificial nest boxes can adversely affect breeding fitness but no great focus has been placed on this issue by researchers. Therefore, we retrieved 321 research papers regarding artificial nest boxes published from 2003 to 2022 and used the ‘Biblioshiny’ program to extract and integrate keywords; we then summarized the adverse effects of artificial nest boxes on avian breeding success. The studies highlighted many drawbacks and misuses in the designing and placement of nest boxes; furthermore, bird attraction was decreased by their inappropriate selection, thus reducing breeding success. Regarding nest box production, there were shortcomings in the construction material, color, smell, and structural design of the boxes used. Nest boxes were also placed at inappropriate densities, locations, orientations, heights, and managed incorrectly. Finally, we propose suggestions for more efficient and safer artificial nest boxes for future use in avian ecology research and bird conservation.

Urbanization brings new selection pressures to wildlife living in cities, and changes in the life-history traits of urban species can reflect their responses to such pressures. To date, most of the studies investigating the impacts of urbanization on avian life-history traits are conducted in Europe and North America, while such studies are often lacking in quickly developing countries in Asia (e.g., China). In this study, we examined the variations in reproductive life-history traits of Chinese Bulbuls (Pycnonotus sinensis) along the urbanization gradient in Hangzhou, China. We detected 234 natural nests of Chinese Bulbuls and continuously monitored them in two continuous breeding seasons from 2012 to 2013. We collected data on seven life-history traits (laying date, incubation period, nestling period, clutch size, egg volume, hatching success rate, and fledging success rate). We used infrared cameras to record the number of feedings per hour as the measure of food resources for the nestlings. We measured nest predation pressure by monitoring 148 natural breeding nests during breeding seasons and 54 artificial nests immediately after breeding seasons. We then calculated the urbanization synthetic index (USI) as a measure of the level of urbanization and examined its relationship with the seven life-history traits. We found that Chinese Bulbuls laid eggs significantly earlier with increasing USI. However, the other six life-history traits did not vary significantly with the USI. Moreover, the feeding frequency of chicks increased significantly with the USI, but the nest predation pressure of Chinese Bulbuls decreased significantly with the USI. Increased food resources and reduced nest predation pressure in cities may lead to earlier laying date of Chinese Bulbuls. Further study should test whether the earlier laying date of Chinese Bulbuls is the result of phenotypic plasticity or genetic change.

Nordmann's Greenshank (Tringa guttifer) is a globally endangered species that has received little research attention. It is threatened by rapid habitat loss, an incomplete network of protected sites, and lack of long-term data on population dynamics. Citizen science data can be combined with survey data to support population estimation and conservation gap analysis. From 2020 to 2021, Nordmann's Greenshank was surveyed in Tiaozini, Xiaoyangkou, and Dongling on the southern coast of Jiangsu Province, China, and the global population of the species was re-evaluated using the data obtained. We integrated citizen science data from eBird and the China Bird Report from 2000 to 2020 with the survey results to identify important habitats harboring over 1% of its total population, and compared this data with existing protected areas to identify gaps in its global conservation. Our survey found that Tiaozini supported at least 1194 individuals. Consequently, its global population was re-estimated to be 1500-2000. Moreover, 45 important habitats were identified based on citizen data and survey results. Although 44.4% and 50.0% of the priority sites in the world and China, respectively, are located outside protected areas, the Conservation Effectiveness Index (C) is 68.4% and 71.1%, respectively, showing that the current coverage of protected areas for this part of its range is reasonable. This study presents the most complete and recent population data to date. Tiaozini is the most important migration stopover site for Nordmann's Greenshanks. The species is under threat in terms of breeding, wintering, and stopover sites. Therefore, we suggest improving monitoring, establishing new protected sites to complete the habitat protection network, and improving the effectiveness of existing habitat protection strategies, including further developing high tide roosting sites.

Providing nest-boxes as surrogate tree cavities can be of great importance to increase the breeding populations of cavity-nesting birds in managed forests. However, the exact placement of nest-boxes should be taken into consideration to enhance their occupancy according to species-specific preferences. In this study, we investigated which factors can better predict nest-box occupancy by the Great Tit (Parus major) in eucalypt plantations. We used generalised linear mixed-effects models to analyse the influence of topography, nest-box positioning, vegetation cover and landscape variables on three-year occupancy records from 80 newly provided nest-boxes. Non-random patterns of nest-box occupancy were found with respect to all categories except topography. Results suggest that Great Tits prefer to occupy high-placed nest-boxes, close to areas that can provide them with supplementary resources either within or in the vicinity of the stand (i.e., trees other than eucalypts, riparian vegetation, and large patches of adjacent habitats). Overall, this study provides important recommendations for nest-box placement and spatial distribution in managed forests and enhances the potential of nest-box interventions as a biodiversity offset and management tool.

Environmentally heterogeneous mountains provide opportunities for rapid diversification and speciation. The family Prunellidae (accentors) is a group of birds comprising primarily mountain specialists that have recently radiated across the Palearctic region. This rapid diversification poses challenges to resolving their phylogeny. Herein we sequenced the complete mitogenomes and estimated the phylogeny using all 12 (including 28 individuals) currently recognized species of Prunellidae. We reconstructed the mitochondrial genome phylogeny using 13 protein-coding genes of 12 species and 2 Eurasian Tree Sparrows (Passer montanus). Phylogenetic relationships were estimated using a suite of analyses: maximum likelihood, maximum parsimony and the coalescent-based SVDquartets. Divergence times were estimated by implementing a Bayesian relaxed clock model in BEAST2. Based on the BEAST time-calibrated tree, we implemented an ancestral area reconstruction using RASP v.4.3. Our phylogenies based on the maximum likelihood, maximum parsimony and SVDquartets approaches support a clade of large-sized accentors (subgenus Laiscopus) to be sister to all other accentors with small size (subgenus Prunella). In addition, the trees also support the sister relationship of P. immaculata and P. rubeculoides ​+ ​P.atrogularis with 100% bootstrap support, but the relationships among the remaining eight species in the Prunella clade are poorly resolved. These species cluster in different positions in the three phylogenetic trees and the nodes are often poorly supported. The five nodes separating the seven species diverged simultaneously within less than half million years (i.e., between 2.71 and 3.15 million years ago), suggesting that the recent radiation is likely responsible for rampant incomplete lineage sorting and gene tree conflicts. Ancestral area reconstruction indicates a central Palearctic region origin for Prunellidae. Our study highlights that whole mitochondrial genome phylogeny can resolve major lineages within Prunellidae but is not sufficient to fully resolve the relationship among the species in the Prunella clade that almost simultaneously diversify during a short time period. Our results emphasize the challenge to reconstruct reliable phylogenetic relationship in a group of recently radiated species.

The song systems of oscine passerines (songbirds) are complex and diverse. Because songs are used for both mate attraction and territory defense and are therefore important signals for survival and reproduction, comprehensive knowledge of within and among species song structure and distribution is informative for understanding the evolution of song repertoires and vocal behaviour. In this study, we explored variation in the song structure of the Ovenbird (Seiurus aurocapilla), a widespread warbler (Family Parulidae) found in North American forests. We analyzed recordings from the 2021 breeding season to assess song type variation at a local (n ​= ​158 birds; Sault Ste. Marie, ON) and breeding range scale (n ​= ​512 birds; eBird). We characterized the local song types and tested whether Ovenbirds share song types with their neighbors more often than expected by chance. We then characterized song types of Ovenbirds across the breeding range to determine whether any geographic pattern of song clustering exists (i.e., macro-dialects). We found 10 distinct song types and some evidence for song type clustering at the local study site (i.e., song neighborhoods). We found 7 of those 10 song types throughout the breeding range and identified an additional 24 types that were not recorded in our local population. We found no evidence for song dialects across the Ovenbird breeding range. This study contributes to our understanding of Ovenbird song while simultaneously adding to our understanding of geographic structuring of warbler repertoires. Our work contributes to delineating a more comprehensive understanding of factors affecting dialect development for this diverse group of songbirds.

The family Alaudidae, larks, comprises 93–100 species (depending on taxonomy) that are widely distributed across Africa and Eurasia, with single species extending their ranges to North and northernmost South America and Australia. A decade-old molecular phylogeny, comprising ~80% of the species, revealed multiple cases of parallel evolution and large variation in rates of morphological evolution, which had misled taxonomists into creating many non-monophyletic genera. Here, we reconstruct the phylogeny of the larks, using a dataset covering one mitochondrial and 16 nuclear loci and comprising all except one of the currently recognised species as well as several recently proposed new species (in total 133 taxa; not all loci available for all species). We provide additional support using genome-wide markers to infer a genus-level phylogeny based on near-complete generic sampling (in total 51 samples of 44 taxa across 40 species). Our results confirm the previous findings of rampant morphological convergence and divergence, and reveal new cases of paraphyletic genera. We propose a new subfamily classification, and also that the genus Mirafra is divided into four genera to produce a more balanced generic classification of the Alaudidae. Our study supports recently proposed species splits as well as some recent lumps, while also questioning some of the latter. This comprehensive phylogeny will form an important basis for future studies, such as comparative studies of lark natural history, ecology, evolution and conservation.

Unintentional food resources in urban areas (street litter, food leftovers, overflowing trash bins) are dietary components of some urban-exploiter bird species. In this study, we report on 13 bird species in six southern Finnish cities using urban trash bins and describe differences in their activity when provided with food resources (i.e., bait) in different bin types. We used generalized linear models (GLM) and classification and regression trees (CART) to test for associations between environmental variables and bird activity at the binscapes. Bird activity at the binscapes significantly differed among all cities and among types of bins and was significantly higher after placing bait in all cases. Bins with the largest opening had more activity as opposed to those with smaller openings or lids. Corvids and gulls had the highest activity, with corvids usually being present before the bait was placed and gulls increasing their activity thereafter. These differences show that trash bin foraging is highly malleable and thus susceptible to management preventing its occurrence. Suitable waste management measures could aid in reducing the number of species close to bins and their surroundings, benefiting both bird and human health.

Harsh environmental conditions often impose strong selection on the phenotype of natural populations through impacts on their fitness. For overwintering birds, winter is an important period for survival because the weather conditions in winter is usually severer than in other seasons and birds often suffer more thermoregulation costs while food is in short supply. Thus, the selective effect of weather conditions on phenotype in winter is expected to be strong. In this study, we examined the relationship of overwinter survival of Silver-throated Tits (Aegithalos glaucogularis) with their morphological traits under different levels of winter conditions (winters with and without snowstorms) to explore the differential selective effect of winter weather on their morphology. We found that regardless of whether the winter experienced a snowstorm, the female Silver-throated Tits with a smaller bill surface area or smaller bill depth and a smaller surface area:volume ratio were more likely to survive during the winter, which supported the hypothesis of selection for heat retention. Furthermore, the females with a smaller body length survived better than the larger females, indicating that the lesser food requirements for smaller body sizes may confer advantages during the winter when food availability was reduced. In addition, in agreement with the finding in many short-lived birds that survival rate increases with the increase of age, older (≥2-year-old) female Silver-throated Tits had higher overwinter survival than 1-year-old females. However, we did not find any correlation of morphological traits and age with survival in male Silver-throated Tits. These results illustrate differential selective effects of winter weather on female and male Silver-throated Tits and contribute to the knowledge of sex-specific selection on the phenotype of natural populations.

The outbreak of the COVID-19 pandemic has brought massive shifts in human activities through a global blockade, directly affecting wildlife survival. However, the indirect impacts of changes in human activities are often easily overlooked. We conducted surveys of Reeves’s Pheasant (Syrmaticus reevesii) and its sympatric species by camera traps in forest-type nature reserves in three different scenarios: pre-lockdown, lockdown and post-lockdown. An increase in livestock activities observed during the lockdown and post-lockdown period in our study area provided us an opportunity to investigate the indirect impact of the lockdown on wildlife. The pre-lockdown period was used as a baseline to compare any changes in trends of relative abundance index, activity patterns and temporal spacing of targeted species and livestock. During the lockdown period, the relative abundance index of livestock increased by 50% and there was an increase in daytime activity. Reeves's Pheasant showed avoidance responses to almost all sympatric species and livestock in three different periods, and the livestock avoidance level of Reeves's Pheasant during the lockdown period was significantly and positively correlated with the relative abundance index of livestock. Species-specific changes in activity patterns of study species were observed, with reduced daytime activities of Hog Badger and Raccoon Dog during and after the confinement periods. This study highlights the effect of the COVID-19 lockdown on the responses of wildlife by considering the changes in their temporal and spatial use before, during and after lockdown. The knowledge gained on wildlife during reduced human mobility because of the pandemic aids in understanding the effect of human disturbances and developing future conservation strategies in the shared space, to manage both wildlife and livestock.

Despite the widely accepted view that planted forests are valuable habitat for wildlife species, there is a lack of empirical evidence showing the suitability of this novel habitat, especially in relation to plantations of exotic tree species. Furthermore, little is known about the effects of forest management on the ecology and dynamics of wild populations in the Neotropics. During the breeding season, the migrant flycatcher White-crested Elaenia is the most abundant bird species in forested landscapes in Chile. For several years we have studied different aspects of these artificial forests in the coastal range of south-central Chile as habitat for the species, particularly in contrast to the native forest. In general, our results indicate that plantation forests offer a poorer quality habitat, where the density of the species tends to be lower than in the native forest, although a significant edge effect suggests that its quality can be mitigated by planting as a matrix mosaic with native forest. Furthermore, compared to native forests, populations in plantations contained a higher proportion of younger adult individuals maintaining larger territories, and showing poorer body condition. We suggest that these differences could also have an impact on the birds’ longevity and survival.

The Oriental Stork (Ciconia boyciana) is listed as ‘Endangered’ on the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species and is classified as a first category nationally protected bird species in China. Understanding this species' seasonal movements and migration will facilitate effective conservation to promote its population. We tagged 27 Oriental Stork nestlings at Xingkai Lake on the Sanjiang Plain in Heilongjiang Province, China, used GPS tracking to follow them over the periods of 2014–2017 and 2019–2022, and confirmed their detailed migratory routes using the spatial analysis function of ArcGIS 10.7. We discovered four migration routes during autumn migration: one common long-distance migration route in which the storks migrated along the coastline of Bohai Bay to the middle and lower reaches of the Yangtze River for wintering, one short-distance migration route in which the storks wintered in Bohai Bay and two other migration routes in which the storks crossed the Bohai Strait around the Yellow River and wintered in South Korea. There were no significant differences in the number of migration days, residence days, migration distances, number of stopovers and average number of days spent at stopover sites between the autumn and spring migrations (P > 0.05). However, the storks migrated significantly faster in spring than in autumn (P ​= ​0.03). The same individuals did not exhibit a high degree of repetition in their migration timing and route selection in either autumn or spring migration. Even storks from the same nest exhibited considerable between-individual variation in their migration routes. Some important stopover sites were identified, especially in the Bohai Rim Region and on the Songnen Plain, and we further explored the current conservation status at these two important sites. Overall, our results contribute to the understanding of the annual migration, dispersal and protection status of the endangered Oriental Stork and provide a scientific basis for conservation decisions and the development of action plans for this species.

Signals within animals' vocal communication are considered functional referential and context-specific. Even in the absence of the context, receivers are expected to acquire the information of calls and respond specifically. Whereas the framework was supported by plenty of evidence, its exhaustivity in describing all animal vocalisations has been questioned. Here, we investigated the vocal repertoire of a cooperatively breeding species, Azure-winged Magpie (Cyanopica cyanus), to present evidence for referential signals. The results showed that Azure-winged Magpies had a relatively large vocal repertoire, consisting of twelve distinct calls. These calls were associated with the context including movement, begging for food, contact, vigilance against predators, etc. However, even the predator-specific alarm calls would induce various responses of receivers. This implies that multiple pieces of information are involved in the vocalisation, which could be utilised by the receiver to select an appropriate response based on the surroundings. Our study gives a detailed description of the context and function of the vocal repertoire in Azure-winged Magpies, laying the foundation for further investigation on the developmental mechanisms of bird vocalisations. This study also suggests that the referential signals of animal vocalisations may not be limited to the context-specific responses of receivers and need to be discussed from a broader perspective.

Nest site selection is a vital component of bird reproduction success, and an adaptive behavior conducted to decrease nest predation risk with avoiding external disturbances. Understanding patterns of nest site selection can provide insights into how species adapt to changes in their habitat and has important conservation implications. In this study, we used microhabitat variables and multi-scale data with a field survey of nest occurrence to determine nest site selection patterns and adaptive strategies of the breeding Oriental Storks (Ciconia boyciana) in different nest areas. Results demonstrate that the nest site microhabitat characteristics of the breeding Oriental Storks significantly differed among the three nesting areas, and nest height was higher in the middle and lower Yangtze River floodplain than in the Northeast China and Bohai Bay nest areas. The food resources and intensity of human disturbance had the greatest effects on the nest site selection of the breeding Oriental Storks. The intensity of human disturbance was positively correlated with the nest height of the breeding Oriental Storks in Bohai Bay and the middle and lower Yangtze River floodplain; however, nest height decreased with the abundance of food resources in the Northeast China nest area. Our findings indicate that the nest site selection patterns of Oriental Storks showed flexible adaptive strategies. In safer environments, nests were lower and closer to food resources, which allows parent storks to invest more in the nestlings. However, in areas where human activity was intense, nests were higher to ensure the safety of their offspring. Some measures that could be taken to improve the breeding habitat of Oriental Storks include increasing the percentage of wetland areas in nesting areas to enhance food resources availability and setting artificial nests at suitable heights in potential nesting grounds to encourage nesting. Finally, the establishment of soft barriers around the nesting areas could increase the safety of nests.

Personality widely exists in diverse animal taxa. Such inter-individual variance in behaviour is supposed to be influenced by social context. However, it remains unknown whether the experience of social life has any carryover effects on the subsequent expression of personality. Here, we examined exploratory behaviour in caged Java Sparrows (Lonchura oryzivora) using exploration assays. Birds were assigned to live in either a solitary or a social context for four weeks. We compared the expressions of exploration before and after the treatments, and found that birds showed higher exploration tendencies after than before social life, while the isolated birds were consistent in their exploratory behaviours. Different living experience led to differences in the exploration activities for birds without significant differences in exploration before. Our results indicate that social experience can make birds more proactive.

Birds maintain complex and intimate associations with a diverse community of microbes in their intestine. Multiple invasive and non-invasive sampling methods are used to characterize these communities to answer a multitude of eco-evolutionary questions related to host-gut microbiome symbioses. However, the comparability of these invasive and non-invasive sampling methods is sparse with contradicting findings. Through performing a network meta-analysis for 13 published bird gut microbiome studies, here we attempt to investigate the comparability of these invasive and non-invasive sampling methods. The two most used non-invasive sampling methods (cloacal swabs and fecal samples) showed significantly different results in alpha diversity and taxonomic relative abundances compared to invasive samples. Overall, non-invasive samples showed decreased alpha diversity compared to intestinal samples, but the alpha diversities of fecal samples were more comparable to the intestinal samples. On the contrary, the cloacal swabs characterized significantly lower alpha diversities than in intestinal samples, but the taxonomic relative abundances acquired from cloacal swabs were similar to the intestinal samples. Phylogenetic status, diet, and domestication degree of host birds also influenced the differences in microbiota characterization between invasive and non-invasive samples. Our results indicate a general pattern in microbiota differences among intestinal mucosal and non-invasive samples across multiple bird taxa, while highlighting the importance of evaluating the appropriateness of the microbiome sampling methods used to answer specific research questions. The overall results also suggest the potential importance of using both fecal and cloacal swab sampling together to properly characterize bird microbiomes.

Sperm competition has been studied in numerous species as a representative example of postcopulatory sexual selection, where sampling sperm from male is the most basic and important step. Sperm collection can be tricky in birds, however, because unlike mammals, the genitals of birds are generally latent in the cloacal region and their characteristics vary among species. Various methods to collect sperm from different birds have been tested, such as cloacal massage, feces collection, and electro-stimulation, but their applicability varies depending on species. In this study, we introduced the urodeum stimulation method (UroS method) to collect sperm from Cuculus cuckoos, such as the Common Cuckoo (C. canorus). These species are expected to have interesting patterns of pair bonding and sperm competition because of their unique breeding strategy called brood parasitism; however, it remains unexplored. In this study, we described the application of our new method to expel semen from male common cuckoos, measured the volume of semen collected, checked the presence of sperm in the semen sample, and finally estimated its success rate among 82 males. Samples were successfully collected from 76 cuckoos (approximately 93%) and the colors and volumes of the samples were very diverse. Sperm was present in 43 of these samples (57%), showing a sperm observation rate approximately twice as high as that of the conventional cloacal massage method. We believe that this novel method will contribute to a better understanding of postcopulatory sexual selection in avian brood parasites and facilitate the process of sperm collection and artificial insemination in other medium-sized birds.

Temperature and other environmental factors play an integral role in the metabolic adjustments of animals and drive a series of morphological, physiological, and behavioral adaptions essential to survival. However, it is not clear how the capacity of an organism for temperature acclimation translates into seasonal acclimatization to maintain survival. Basal metabolic rate (BMR), evaporative water loss (EWL), and energy budget were measured in the Chinese Hwamei (Garrulax canorus) following winter and summer acclimatization, and in those acclimatized to 15 ​℃ (cold) and 35 ​℃ (warm) under laboratory conditions for 28 days. In addition to the above indicators, internal organ masses, as well as state 4 respiration and cytochrome c oxidase (COX) activity were also measured for the liver, skeletal muscle, heart, and kidney. Both winter-acclimatized and cold-acclimated birds exhibited significantly higher BMR, EWL, and energy budget, as well as organ masses, state 4 respiration, and COX activity compared with the summer-acclimatized and warm-acclimated birds. This indicated that the Chinese Hwamei could adapt to seasonal or just temperature changes through some physiological and biochemical thermogenic adjustments, which would be beneficial to cope with natural environmental changes. A general linear model showed that body mass, BMR, GEI, state 4 respiration in the liver and kidney, and COX activity in the skeletal muscle, liver, and kidney were significantly affected by temperature and acclimation. A positive correlation was observed between BMR and each of the other parameters (body mass, EWL, energy budget, heart dry mass, kidney dry mass, state 4 respiration) in the muscle, heart, and kidney and also between BMR and COX activity in the muscle and kidney. The results suggested that similar to seasonal acclimatization, Chinese Hwameis subjected to temperature acclimation also exhibited significant differences in metabolism-related physiological and biochemical parameters, depending on the temperature. The data also supported the prediction that metabolic adjustment might be the primary means by which small birds meet the energetic challenges triggered by cold conditions.

The Hooded Crane (Grus monacha) is listed as a Vulnerable species in the IUCN red list. Tidal wetland (tideland), the major habitat for wintering Hooded Cranes at East China's Chongming Dongtan, has dramatically changed in the past two decades, but there is limited knowledge about the population and habitat changes of the Hooded Cranes. This study investigated the population size and distribution of wintering Hooded Cranes at Chongming Dongtan from 2000 to 2021. We used remote sensing images combined with a vegetation classification algorithm to analyse the distribution of saltmarsh vegetation. The quadrat method was used to investigate the density and weight of the underground corms of Sea Bulrush (Scirpus mariquter), the main food on tideland for the Hooded Cranes. From 2000 to 2021, the population number of wintering Hooded Cranes at Chongming Dongtan remained stable at approximately 100. In 2000, the area of Scirpus spp. and Common Reed (Phragmites australis) accounted for approximately half of the total saltmarsh area at Chongming Dongtan, respectively. The invasive Smooth Cordgrass (Spartina alterniflora) rapidly expanded on tideland in the 2000s while the Scirpus spp. was competed out and thus significantly reduced in area. After the implementation of an ecological project to control Smooth Cordgrass and to restore Scirpus spp. in the 2010s, the area of the Smooth Cordgrass decreased considerably while the area of Scirpus spp. increased. The corms of Sea Bulrush decreased on the southeastern tideland during the study period, which might be the cause of the northward movement of the foraging Hooded Cranes on tideland. We also found Hooded Cranes foraged crops in the nearby farmland in mid-winter, causing human-bird conflicts in the recent decade. Our results found that changes in habitat and food conditions on tideland impacted wintering Hooded Cranes. Foraging in farmland with human disturbance in the recent decade might be related to insufficient food on tideland. We suggest active intervention to accelerate the restoration of Sea Bulrush on tideland and reduce human disturbance in farmland to improve the habitat quality of the wintering Hooded Crane at Chongming Dongtan.

The breeding traits of Sporophila seedeaters have been relatively well studied in recent years; nevertheless, a group of ten species in the genus, known as southern capuchinos, remain understudied. That is the case with Chestnut Seedeater (Sporophila cinnamomea), a species vulnerable to extinction, which breeds in the grasslands of southeast South America and, after reproduction, migrates towards the Cerrado region in central Brazil. Here, we investigated breeding ecology and calculated average clutch size, productivity, the sex ratio of nestlings, and estimated nest success. Then we tested (1) whether there is a relationship between the number of active nests and environmental variables, (2) whether the nestling sex ratio deviates from the 1:1 ratio, (3) whether clutch size varies between breeding seasons, and (4) whether the nest success is related to starting date, nest age, plant support, nest height from the ground, and clutch size. During two breeding seasons (October–March 2018–2020), we monitored 98 nests. We generated survival models with five interacting covariates to assess the survival of the nests. We recorded the entire breeding period for Chestnut Seedeater, which was estimated to be 4.6 months, similar to other migratory seedeaters. Clutch size did not differ between breeding seasons. The sex ratio of nestlings was not significantly different from the 1:1 ratio. Nest success was 31%, and predation was the leading cause of unsuccessful nests (83%). The daily survival rate was 0.95 ​± ​0.01. The main predictor of nest survival was the covariate starting date. These findings, added to other aspects of the species' natural history described here, may help illuminate the ecology and behavior of Chestnut Seedeater and other southern endangered capuchinos, and grassland-dependent species of South America.

Avian malaria and related haemosporidian parasites can negatively impact fitness in many songbirds. Research on the malaria infection and its physiological costs on their avian hosts is heavily skewed toward native passerines, with exotic species underrepresented. However, introduced species may carry on and spread new pathogens to native species, and play a role on parasite transmission cycle in invaded bird communities as pathogen reservoir. Here, we molecularly assess the prevalence and diversity of haemosporidian parasites in three introduced wetland passerines (the Red Avadavat Amandava amandava, the Yellow-crowned Bishop Euplectes afer, and the Common Waxbill Estrilda astrild) captured during the same season in southwestern Spain. We also explored the relation between parasite infection, body condition, haematocrit, and uropygial gland volume. We detected an overall parasite prevalence of 3.55%, where Common Waxbills showed higher prevalence (6.94%) than Red Avadavats (1.51%). None Yellow-crowned Bishops were infected with haemosporidians. Almost 60% of infections were caused by Leucocytozoon, and about 40% by Plasmodium. We identified four unique lineages of Plasmodium and three of Leucocytozoon. Moreover, 91% of the identified host–parasite interactions represented new host records for these haemosporidian parasites. Parasite infection was not related to body condition, haematocrit, and uropygial gland volume of the wetland passerines. Haematocrit values varied seasonally among bird species. Additionally, haematocrit was positively related to body condition in the Yellow-crowned Bishops, but not in the other species. Red Avadavats had higher haematocrit levels than Yellow-crowned Bishops, whereas Common Waxbills showed the lower haematocrit values. The uropygial gland volume was positively correlated with body condition in all bird species. Common Waxbills showed higher uropygial gland volumes related to their body size than birds from other two species. These outcomes highlight the importance of exotic invasive species in the transmission dynamics of haemosporidian parasites.

Binomial N-mixture models are commonly applied to estimate abundance unaffected by imperfect detection, but are known to be sensitive to violations of assumptions. One of the model's assumptions, the independence of detections has rarely been tested. It requires that during a survey, detection of one individual does not affect detection of another individual. This assumption can be frequently violated in passerine birds, which exhibit territorial behaviour by singing, since neighbouring individuals are likely to motivate each other to vocalize, leading to non-independence in singing activity and in the following detection rate. Here, we explored this phenomenon with the generalized, binomial version of the N-mixture model, where detection probability is decomposed into availability probability φ – which can be interpreted as per capita song rate or the probability of vocalising – and actual detection probability p, given vocalisations take place. Using repeated counts of the Collared Flycatcher (Ficedula albicollis) as a case study, and treating the maximum observed counts C at a site i as an explanatory covariate for φ, we showed that per capita song rates increased with observed counts at a site. Hence, if song rates vary due to local abundance, including C as an explanatory variable for song rate addressed with φ, helps to explain this variation (which otherwise goes undetected) and improves inferences under the model. This had strong effects on the resulting abundance estimates: if this relationship was ignored in the models, total estimated population sizes were consequently lower by as much as 22–27%, compared to when this effect was included. Since it is likely that song rates may commonly be density-dependent in birds manifesting territorial behaviours by singing, further tests addressing violations of independence assumptions in these models are needed. As suggested by Kéry and Royle (2016), despite some form of circularity likely being involved, modelling heterogeneity in the detection process with the help of C in standard N-mixture models (which, given availability, conflate availability with detection in a single parameter) should be applicable as well.

Climate exerts a dominant control over the distribution of species. Generally, species migrate to higher elevations to track thermal niches, but variations in morphological traits can result in trait-specific responses to climate change. Here we attempted to explore how three sympatrically distributed raptor species (the Upland Buzzard Buteo hemilasius, UB; the Common Kestrel, also called Eurasian ​Kestrel Falco tinnunculus, EK; and the Saker Falcon Falco cherrug, SF) would respond to climate change over time, and whether their responses would bias by different morphology. We tested the alternative hypotheses for Allen's rule for UB, EK, and SF in Qinghai Province, China, by modeling their current and future habitat suitability and confirming whether a consistent pattern exists between climate-induced range shifts and morphological differences among species. The extent of the projected distribution range within protected areas was also calculated for each species. We identified the future downward elevation shift for all the species, but with the notable northeastward shifting of the suitable climate space for UB and SF. Climate change would induce range contraction in the future, and the most acute influence is always the result of the pessimistic SSP585 scenario. No obvious pattern in climate-induced range shift was found for EK, for whom the morphological traits were significantly smaller all the time. More seriously, the ratios of highly suitable habitats being protected for our three raptor species were almost at a deficient level (below 1%). This study firstly tested the alternative hypothesis of Allen's rule among raptors in Qinghai Province unprecedently, confirmed the morphological basis for different responses to changing climate across species, and demonstrated the protection deficiency under the current protected area design. We advocate more related studies in the future to verify our findings across more taxa.

Evaluating the genetic status of threatened species is an essential task in conservation genetics. However, the genetic status of threatened species has been mostly evaluated through techniques that fail to estimate genetic diversity at the whole genomic level. Next generation sequencing can meet this demand, but high quality samples such as blood or muscle tissues are required. However, it is difficult to collect such samples from threatened species because sampling work may impact their health. Therefore, it is essential to design a workflow to evaluate the whole genomic status of threatened species using non-destructive sampling. Even though non-destructive sampling has been used in traditional barcoding technique, the barcoding technique cannot evaluate the whole genomic status. Brown Eared Pheasant (Crossoptilon mantchuricum) is an endangered species, with captive populations maintained in Taiyuan Zoo, China, and Europe. However, the genetic diversity, inbreeding pattern, and mutation load of these two populations are unclear. To uncover the genetic status of these two captive populations, we applied 2b-RAD technology to evaluate the genomic status of these populations using feathers as samples. The feathers could be collected by non-destructive sampling. The results indicate that the Taiyuan Zoo population has a lower genetic diversity and higher inbreeding coefficient than the European population. The Taiyuan Zoo population has lethal mutations when homozygous. The current project uses a non-destructive sampling technique to evaluate the whole genomic status of the two captive populations, providing a paradigm for conservation genetics, which will facilitate the development of conservation biology.

Adaptive mate choice has been accepted as the leading theory to explain the colorful plumage of birds. This theory hypothesizes that conspicuous colors act as signals to advertise the qualities of the owners. However, a dilemma arises in that conspicuous colors may not only attract mates, but also alert predators. The "private channels of communication" hypothesis proposes that some intraspecific signals may not be visible to heterospecific animals because of different visual systems. To better understand the evolution of plumage colors and sexual selection in birds, here we studied the chromatic difference and achromatic differences of melanin- and carotenoid-based plumage coloration in five minivet species (Pericrocotus spp.) under conspecific and predator visual systems. We found that either the chromatic or achromatic difference among male or female minivets' plumage was consistently higher under conspecific vision than under predator vision for all five studied species of minivets. This result indicated that individual differences in plumage colors of minivets were visible to the conspecific receivers and hidden from potential predators as a result of evolution under predation risk and conspecific communication. However, males were under a higher risk of predation because they were more conspicuous than females to the vision of a nocturnal predator.

Long-distance migratory birds often face major geographical barriers on their journey. While some species are able to cross them, others use longer routes to avoid such barriers. Little is known about the strategies of Siberian landbird migrants, which either cross or circumvent the deserts and mountain ranges of Central Asia en route to their non-breeding sites in Southeast Asia. Here we compare data on migration phenology and morphology from two bird ringing stations in eastern Russia, situated at similar latitudes but with a longitudinal difference of 1500 ​km, to hypothesise migration patterns. We found significant differences in timing between the two sites (birds migrated significantly earlier in spring and significantly later in autumn in the east), suggesting longitudinal migration as a result of migration detour. However, morphological differences show a less clear pattern. We argue that most Siberian landbirds might opt for a detour through the Russian Far East instead of a direct route in order to avoid unfavourable stop-over habitat in Central Asia. However, tracking studies will be necessary to prove this.

Niche partitioning is a widespread ecological strategy within trophic guilds, ensuring the coexistence of sympatric species by reducing interspecific competition. Stable isotope analysis of carbon and nitrogen and isotopic niche metrics (width and overlap) are used as a proxy to investigate niche partitioning among species of a guild. In our study, we investigated if niche partitioning was an ecological mechanism contributing to the coexistence of granivorous birds from the same geographic region along time, employing an isotopic approach. We sampled and isotopically analyzed (δ¹³C and δ¹⁵N values) wing feathers from 58 specimens of granivorous birds collected between 1900 and 1966 in southeastern Brazil. We grouped birds according to the main habitat type used by them (forest: Cyanoloxia brissonii, Leptotila rufaxilla, and Leptotila verreauxi; and grassland: Columbina squammata and Sicalis flaveola). We used the Isotopic Richness (IRic) metric to measure the isotopic niche width and the Isotopic Similarity (ISim) and Isotopic Nestedness (INes) metrics to measure the niche overlap between groups and species. The results of low isotopic niche overlap suggest that common granivorous birds had a clear niche partitioning in southeastern Brazil in the late past, especially through foraging in distinct habitat types (forest and grassland; ISim ​= ​0.1, INes ​= ​0.2). Niche overlaps in almost all species-by-species comparisons were low (ISim ≤0.3, INes ≤0.4), except between C. brissonii and L. verreauxi (ISim ​= ​0.6, INes ​= ​1.0). These results suggest that these birds, belonging to the same trophic guild, coexisted through niche and resource partitioning. Despite being considered a plastic trophic guild, the isotopic niche partitioning among granivorous birds indicates that each of these species uses a set of specific resources and habitats. This raises an ecological concern about the homogenization of landscapes across the Neotropics, oversimplifying food resources and habitats to granivorous birds.

Urbanization is currently considered one of the most rapid types of global environmental change. Urban habitats are biotically and abiotically different from their rural areas, i.e., the ambient temperature, predator, and food availability. These novel challenges create new selection pressures, which allow one to investigate eco-evolutionary responses to contemporary environmental change. A total of 118 breeding nests were monitored for nest predation in both urban and rural areas from 2018 to 2020. We used environmental factors from urban and rural areas and behavioral data from 439 Chinese Blackbird (Turdus mandarinus) valid incubation days to understand the impact of urbanization on the incubation behavior of blackbirds and its adaptation mechanism to the urban environment. Cities have warmer ambient temperatures and lower predation pressures than rural areas. Urban blackbirds chose the incubation strategy with shorter and more bouts, while rural blackbirds selected the incubation strategy with longer and fewer bouts. The plasticity of incubation behavior of urban blackbirds was higher than that of rural areas, and the range of egg temperature was also higher than that of rural areas. In addition, incubation temperature and the number of bouts per day were the key factors affecting the day survival rate of blackbirds, and the hatching rate of urban blackbirds was higher than that of rural blackbirds. Our results provide evidence for behavioral shifts in blackbirds during adaptation to urbanization and support the central role of behavioral adaptation in the successful colonization of new environments by wildlife. These help us understand the behavioral characteristics required for wildlife to live in cities and the urban adaptors faced environmental pressures.

Pallid Swifts (Apus pallidus), as other swifts, are birds extremely adapted to an aerial lifestyle, showing unique adaptations that allow them to fly almost continuously. The diet of these non-stopping high-altitudinal aerial birds has been mostly studied through techniques that fail to produce highly resolved prey identifications, and for that have been replaced by molecular techniques, such as DNA metabarcoding. Faecal samples of Pallid Swifts were monthly collected from a colony in the north of Portugal during the breeding season. DNA from the faecal samples was used to sex the birds and to identify the arthropods present in the diet through DNA metabarcoding. From the detected prey items, 74 families were identified belonging to 16 orders, with Hymenoptera and Hemiptera being the most frequently consumed. There were seasonal variations in diet richness, composition and prey size. Regarding the diet of males and females, although no differences were found between the diet of males and females in terms of composition and richness, there were differences in the size of arthropods preyed by the different sexes, with males feeding on larger arthropods. The large seasonal variation in Pallid Swifts' diet during the breeding season is probably a result of spatiotemporal variation in aerial prey, of which swifts likely predate opportunistically. Although no significant differences were detected in diet richness and composition between sexes, the fact that males consumed larger prey may suggest the existence of sexual dietary segregation in this group of birds. At last, several pest species were found in these swifts' diet, which, if studied through DNA metabarcoding, can be used to monitor small arthropods, including airborne pests.

According to one of the theses of optimal foraging theory, main prey species abundance in the hunting area is the main factor determining the diet and habitat choices of birds of prey. However other factors can also be important. The habitat structure influences the predators' diets as well. In this study we examined the influence of habitat structure on diet compositions of three species of birds: Long-eared Owl (Asio otus), Short-eared Owl (A. flammeus) and Common Kestrel (Falco tinnunculus). The study was carried out from 2007 to 2019 in a 48 ​km² area of the Crane's Homeland Reserve, Moscow Region, Russia. The habitat structures of model species' hunting territories (ratio of different types of landscape elements) were classified in module "Semi-Automatic Classification Plugin" based on the QGIS. A boosted regression tree analysis identified that the share of the main prey species in the diet is primarily determined by the landscape structure of hunting territories. The largest share of Common Vole (Microtus arvalis) in birds' diet was determined by the shrubs area (15% of hunting area), the meadow area (75%), the habitat heterogeneity (70%) and the arable land area (5%). The same predictors determined the largest share of Root Vole (Microtus oeconomus): the shrubs area 25%, the meadow area 70%, and the arable land area 3%. The annual mean abundance of prey species did not determine their importance in the diet of birds of prey. Thus, the main prey abundance in the hunting area is not a determining factor for the formation of diet composition of birds of prey.

A determination of how the color of animal integument is produced is a starting point for investigations into the function and evolution of coloration. The mechanisms that give rise to the color of bare skin of New World vultures are largely unexplored. Here, we investigate the source of color production in the bare skin of Turkey Vultures (Cathartes aura) and Black Vultures (Coragyps atratus). Using UV–vis reflectance spectroscopy, we found evidence that hemoglobin is the primary pigment responsible for the red coloration of the bare skin on the heads of Turkey Vultures, and that eumelanin is responsible for the black coloration of the bare skin on the heads of Black Vultures. Light microscopy of incisional skin samples further supported these mechanisms of color production by revealing the presence of numerous blood vessels near the surface of the Turkey Vulture skin, and a high concentration of melanosomes in the skin of Black Vultures. Using high performance liquid chromatography (HPLC), we detected carotenoids within the skin of both species with significantly higher total concentrations of carotenoids in the skin of Turkey Vultures compared to the skin of Black Vultures. The carotenoids detected were dietary carotenoids that typically produce yellow coloration when accumulated in integument and were present in low concentrations. We hypothesize that the dietary carotenoids present do not contribute to the color of the skin, but rather help to compensate for the lack of melanosomes found in Turkey Vulture skin. The presence of additional carotenoids may act as an antioxidant to minimize UV damage when the bare Turkey Vulture head skin is exposed to direct sunlight for prolonged periods of time when soaring and scavenging for food.

Thermogenic features are often invoked to illustrate animal's colonization, distribution, and response to climate change. To understand why the White-browed Laughingthrush (Pterorhinus sannio) has expanded its distribution to temperate zones in recent years, we compared its thermogenic features with three species of songbirds that co-occur in its newly colonized areas. Thermogenic parameters of these four species were measured under different ambient temperatures, ranging from 0 to 40 ​℃. The results showed that basal metabolic rate (BMR) was 44.5 ​± ​3.9 ​mL O₂/h in P. sannio, which is lower than predicted value by its body weight. This is also lower than the BMR of both its temperate congener the Plain Laughingthrush (P. davidi) and the montane, similar species Elliot's Laughingthrush (Trochalopteron elliotii). The thermal neutral zone (TNZ) in P. sannio was 15–35 ​℃, as compared to 10–27.5 ​℃ in P. davidi, 25–30 ​℃ in T. elliotii, and 7.5–32.5 ​℃ in the Green-capped Greenfinch (Chloris sinica). Thermal conductance was lowest in P. sannio, with the minimum value lower than the predicted value based on its body weight. Our results showed that the northward-colonizing P. sannio exhibited different thermogenic characteristics compared with its coexisting species in the new habitat, even its congener P. davidi, which shared similar microhabitats to P. sannio. We suggest that researchers further explore the physiological mechanisms of birds' northward expansion.

Until recently, Limosa limosa melanuroides was thought to be the only subspecies of Black-tailed Godwit in the East Asian–Australasian Flyway. For this reason, all previous occurrences and counts of Black-tailed Godwits in the flyway have been assigned to melanuroides. However, a larger-bodied subspecies, bohaii, has recently been discovered in the flyway. As a result, the occurrence of Black-tailed Godwits in the flyway needs to be reconsidered such that the specific distribution of each subspecies becomes known. To this end, we developed a simple discriminant function to assign individuals to subspecies based on their bill and wing length. Cross-validation with individuals known to be bohaii or melanuroides, based on molecular analysis, showed the developed function to be 97.7% accurate. When applied to measurements of godwits captured at 22 sites across 9 countries in East–Southeast Asia and Australia, we found that bohaii and melanuroides occurred at most sites and overlapped in their distribution from Kamchatka to Australia. We examined photos from all along the flyway to verify this surprising result, confirming that both subspecies co-occur in most locations. Based on these results, we hypothesise that bohaii and melanuroides from the west of their breeding ranges mostly migrate over Chinese mainland. Birds of both subspecies from the east of their ranges are expected to migrate along the Pacific Ocean. We encourage ringing groups in East–Southeast Asia and Australia to use this simple method to keep adding knowledge about Black-tailed Godwits in the East Asian–Australasian Flyway.