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.

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.

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.

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.