May brood desertion be ruled by partner parenting capability in a polygamous songbird? An experimental study.

Parents confront multiple aspects of offspring demands and need to coordinate different parental care tasks. Biparental care is considered to evolve under circumstances where one parent is not competent for all tasks and cannot efficiently raise offspring. However, this hypothesis is difficult to test, as uniparental and biparental care rarely coexist. Chinese penduline tits (Remiz consobrinus) provide such a system where both parental care types occur. Here, we experimentally investigated whether parents in biparental nests are less capable of caring than parents in uniparental nests. We monitored parenting efforts at (1) naturally uniparental and biparental nests and (2) biparental nests before and during the temporary removal of a parent. Given the relatively small sample sizes, we have employed various statistical analyses confirming the robustness of our results. We found that total feeding frequency and brooding duration were similar for natural uniparental and biparental nests. Feeding frequency, but not brooding duration, contributed significantly to nestling mass. In line with this, a temporary parental removal revealed that the remaining parents at biparental nests fully compensated for the partner's feeding absence but not for brooding duration. This reflects that the manipulated parents are confronted with a trade-off between feeding and brooding and were selected to invest in the more influential one. However, such a trade-off may not occur in parents of natural uniparental care nests. The different capabilities of a parent independently coordinating feeding and brooding tasks suggest that parents from biparental and uniparental nests were exposed to different resource conditions, thereby foraging efficiency may differ between care types.

Spatiotemporal genotype replacement of H5N8 avian influenza viruses contributed to H5N1 emergence in 2021/2022 panzootic.

Since 2020, clade 2.3.4.4b highly pathogenic avian influenza H5N8 and H5N1 viruses have swept through continents, posing serious threats to the world. Through comprehensive analyses of epidemiological, genetic, and bird migration data, we found that the dominant genotype replacement of the H5N8 viruses in 2020 contributed to the H5N1 outbreak in the 2021/2022 wave. The 2020 outbreak of the H5N8 G1 genotype instead of the G0 genotype produced reassortment opportunities and led to the emergence of a new H5N1 virus with G1's HA and MP genes. Despite extensive reassortments in the 2021/2022 wave, the H5N1 virus retained the HA and MP genes, causing a significant outbreak in Europe and North America. Furtherly, through the wild bird migration flyways investigation, we found that the temporal-spatial coincidence between the outbreak of the H5N8 G1 virus and the bird autumn migration may have expanded the H5 viral spread, which may be one of the main drivers of the emergence of the 2020-2022 H5 panzootic.IMPORTANCESince 2020, highly pathogenic avian influenza (HPAI) H5 subtype variants of clade 2.3.4.4b have spread across continents, posing unprecedented threats globally. However, the factors promoting the genesis and spread of H5 HPAI viruses remain unclear. Here, we found that the spatiotemporal genotype replacement of H5N8 HPAI viruses contributed to the emergence of the H5N1 variant that caused the 2021/2022 panzootic, and the viral evolution in poultry of Egypt and surrounding area and autumn bird migration from the Russia-Kazakhstan region to Europe are important drivers of the emergence of the 2020-2022 H5 panzootic. These findings provide important targets for early warning and could help control the current and future HPAI epidemics.

Divergent Selection in Low Recombination Regions Shapes the Genomic Islands in Two Incipient Shorebird Species.

Speciation in the face of gene flow is usually associated with a heterogeneous genomic landscape of divergence in nascent species pairs. However, multiple factors, such as divergent selection and local recombination rate variation, can influence the formation of these genomic islands. Examination of the genomic landscapes of species pairs that are still in the early stages of speciation provides an insight into this conundrum. In this study, population genomic analyses were undertaken using a wide range of sampling and whole-genome resequencing data from 96 unrelated individuals of Kentish plover (Charadrius alexandrinus) and white-faced plover (Charadrius dealbatus). We suggest that the two species exhibit varying levels of population admixture along the Chinese coast and on the Taiwan Island. Genome-wide analyses for introgression indicate that ancient introgression had occurred in Taiwan population, and gene flow is still ongoing in mainland coastal populations. Furthermore, we identified a few genomic regions with significant levels of interspecific differentiation and local recombination suppression, which contain several genes potentially associated with disease resistance, coloration, and regulation of plumage molting and thus may be relevant to the phenotypic and ecological divergence of the two nascent species. Overall, our findings suggest that divergent selection in low recombination regions may be a main force in shaping the genomic islands in two incipient shorebird species.

Metabarcoding of fecal DNA reveals the broad and flexible diet of a globally endangered bird.

Knowing the diet of endangered wild animals is a prerequisite for species-specific conservation and habitat management. The Sichuan partridge Arborophila rufipectus is a globally endangered Galliformes species endemic to the mountains of southwest China. Existing information on the diet of this species is biased and fragmented owing to traditional observation methods. Little is known about their dietary composition or how they respond to temporal variations in food resources throughout the year. In this study, a dietary analysis was performed on 60 fecal samples using DNA Metabarcoding of invertebrates and plants to determine the primary animal and plant components of the diet across 3 critical periods of adult life history (breeding, postbreeding wandering, and overwintering). Preys from the dipteran order, followed by the lepidopteran and araneaen spp., were the predominant, animal-derived foods. Symplocos, Rubus, Celastrus, Holboellia, and Actinidia spp. supply a large abundance of fruits and seeds for this omnivorous bird. Substantial temporal dietary changes among the 3 periods and a general shift toward lower dietary diversity during the breeding season were observed, suggesting that the Sichuan partridge can adjust their diet according to the availability of food resources and their own needs. Characterizing the composition and seasonal changes in Sichuan partridge diets informs the habitat management of native flora (the plant taxa that can generate berries and seeds, such as Symplocos, Rubus, Celastrus, and Holboellia, which are likely of conservation interest) to achieve full life-cycle conservation.

Temporal Variations in the Gut Microbiota of the Globally Endangered Sichuan Partridge (Arborophila rufipectus): Implications for Adaptation to Seasonal Dietary Change and Conservation.

Host-associated microbiotas are known to influence host health by aiding digestion, metabolism, nutrition, physiology, immune function, and pathogen resistance. Although an increasing number of studies have investigated the avian microbiome, there is a lack of research on the gut microbiotas of wild birds, especially endangered pheasants. Owing to the difficulty of characterizing the dynamics of dietary composition, especially in omnivores, how the gut microbiotas of birds respond to seasonal dietary changes remains poorly understood. The Sichuan partridge (Arborophila rufipectus) is an endangered pheasant species with a small population endemic to the mountains of southwest China. Here, 16S rRNA sequencing and Tax4Fun were used to characterize and compare community structure and functions of the gut microbiota in the Sichuan partridges across three critical periods of their annual life cycle (breeding, postbreeding wandering, and overwintering). We found that the microbial communities were dominated by Firmicutes, Proteobacteria, Actinobacteria, and Cyanobacteria throughout the year. Diversity of the gut microbiotas was highest during postbreeding wandering and lowest during the overwintering periods. Seasonal dietary changes and reassembly of the gut microbial community occurred consistently. Composition, diversity, and functions of the gut microbiota exhibited diet-associated variations, which might facilitate host adaptation to diverse diets in response to environmental shifts. Moreover, 28 potential pathogenic genera were detected, and their composition differed significantly between the three periods. Investigation of the wild bird gut microbiota dynamics has enhanced our understanding of diet-microbiota associations over the annual life cycle of birds, aiding in the integrative conservation of this endangered bird. IMPORTANCE Characterizing the gut microbiotas of wild birds across seasons will shed light on their annual life cycle. Due to sampling difficulties and the lack of detailed dietary information, studies on how the gut microbiota adapts to seasonal dietary changes of wild birds are scarce. Based on more detailed dietary composition, we found a seasonal reshaping pattern of the gut microbiota of Sichuan partridges corresponding to their seasonal dietary changes. The variation in diet and gut microbiota potentially facilitated the diversity of dietary niches of this endangered pheasant, revealing a seasonal diet-microbiota association across the three periods of the annual cycle. In addition, identifying a variety of potentially pathogenic bacterial genera aids in managing the health and improving survival of Sichuan partridges. Incorporation of microbiome research in the conservation of endangered species contributes to our comprehensive understanding the diet-host-microbiota relationship in wild birds and refinement of conservation practices.

Egg characteristics vary longitudinally in Arctic shorebirds.

Arctic environments are changing rapidly and if we are to understand the resilience of species to future changes, we need to investigate alterations in their life histories. Egg size and egg shape are key life-history traits, reflecting parental investment as well as influencing future reproductive success. Here we focus on egg characteristics in two Arctic shorebirds, the Dunlin (Calidris alpina) and the Temminck's stint (Calidris temminckii). Using egg photos that encompass their full breeding ranges, we show that egg characteristics exhibit significant longitudinal variations, and the variation in the monogamous species (Dunlin) is significantly greater than the polygamous species (Temminck's stint). Our finding is consistent with the recent "disperse-to-mate" hypothesis which asserts that polygamous species disperse further to find mates than monogamous species, and by doing so they create panmictic populations. Taken together, Arctic shorebirds offer excellent opportunities to understand evolutionary patterns in life history traits.

First breeding record of the black-headed penduline tit (Remiz macronyx) in China.

Black-headed penduline tit (Remiz macronyx) is a poorly known bird species mainly distributed in Iran, Turkmenistan, and Kazakhstan. The distribution of black-headed penduline tit is disjointed and fragmented, and it occurs only along lakes or rivers surrounded by extensive reedbeds. Four subspecies of R. macronyx have been recognized (macronyx, neglectus, nigricans, and ssaposhnikowi). The ssaposhnikowi subspecies was previously known to occur only around lakes in southeastern Kazakhstan. In this study, we reported the first confirmed breeding record of R. m. ssaposhnikowi in the Nalati wetland, Ili, Xinjiang, China, extending the distribution range of the black-headed penduline tit by 350 km to the east. We also obtained new information about the morphology and breeding behavior of R. m. ssaposhnikowi, which can be useful for the taxonomy of penduline tits, especially in distinguishing black-headed penduline tits from Eurasian penduline tits (R. pendulinus).

Mammalian predators and vegetated nesting habitat drive reduced protected area nesting success of Kentish plovers, Yellow Sea region, China.

Protected areas provide essential habitats for wildlife by conserving natural and semi-natural habitats and reducing human disturbance. However, whether breeding birds vulnerable to nest predation can benefit from strict land management in the protected area is unclear. Here, we compare the nesting performance of two groups of a ground-nesting shorebird, the Kentish plover (Charadrius alexandrinus), in the protected area (Liaohekou Natural Reserve, hereinafter PA), and the control non-protected area (non-PA) around the Liaohekou Natural Reserve, in the north of the Yellow Sea, China, and identify which environmental factors, such as nesting habitat and nest materials, influence the daily nest survival rate (DSR). We found similar nesting habitats in both study areas, dominated by bare land or Suaeda salsa grassland. However, DSR was lower in PA (0.91 ± 0.01) than in non-PA (0.97 ± 0.01). Kentish plovers nesting in areas with vegetation cover experienced lower DSR than in bare lands in both areas, and nests built with materials of S. salsa sticks had the lowest DSR in the bare land. Data from infrared cameras confirmed relatively higher predator abundances and nest predation rates by nocturnal mammals, such as Eurasian badgers (Meles meles), in PA than in non-PA, and this pattern was especially evident for plover nests located in S. salsa grassland. Our results suggest that Liaohekou Natural Reserve protected area may not necessarily provide safe nesting sites for Kentish plovers due to the abundance of generalist mammal nest predators. However, the PA includes about 80% of the nests from both locations. This means the contribution of the total number of successful nests continues to be much higher within PA, with the benefit for the species that this brings in terms of conservation. The variation and mechanisms underlying differences in the nest predator communities of PA and non-PA deserve further study.

Inter-glacial isolation caused divergence of cold-adapted species: the case of the snow partridge.

Deciphering the role of climatic oscillations in species divergence helps us understand the mechanisms that shape global biodiversity. The cold-adapted species may have expanded their distribution with the development of glaciers during glacial period. With the retreat of glaciers, these species were discontinuously distributed in the high-altitude mountains and isolated by geographical barriers. However, the study that focuses on the speciation process of cold-adapted species is scant. To fill this gap, we combined population genetic data and ecological niche models (ENMs) to explore divergence process of snow partridge (Lerwa lerwa). Lerwa lerwa is a cold-adapted bird that is distributed from 4,000 to 5,500 m. We found 2 genetic populations within L. lerwa, and they diverged from each other at about 0.40-0.44 million years ago (inter-glacial period after Zhongliangan glaciation). The ENMs suggested that L. lerwa expanded to the low elevations of the Himalayas and Hengduan mountains during glacial period, whereas it contracted to the high elevations, southern of Himalayas, and Hengduan mountains during inter-glacial periods. Effective population size trajectory also suggested that L. lerwa expanded its population size during the glacial period. Consistent with our expectation, the results support that inter-glacial isolation contributed to the divergence of cold-adapted L. lerwa on Qinghai-Tibetan Plateau. This study deepens our understanding of how climatic oscillations have driven divergence process of cold-adapted Phasianidae species distributed on mountains.

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Oil and its pollutants, which enter environment through natural oil seepage and many human activities, have considerable impacts on birds. We summarized the research advances in how oil pollutants influence birds and the cleaning technology of polluted birds and their habitats. The toxicity and destruction to feather structure are the major impacts of oil pollution on birds. Oil pollution can lead to birds' death, and also produce many chronic harms, including causing hemolytic anemia, reducing their immunity, disrupting thermal insulation and waterproo-fing performance of feather. It is an important way to reduce the impacts of oil pollution on birds by timely cleaning up the oil in bird habitats as well as carrying out the clean and repair work to the polluted birds. As a big oil-consuming country, China has been left behind by foreign countries in the studies of the effects of oil pollution on birds. More attention should be paid on the short-term and long-term impacts of oil pollution on birds and the cleaning and remediation technologies of the polluted birds and their habitats.

Genomic status of yellow-breasted bunting following recent rapid population decline.

Global biodiversity is facing serious threats. However, knowledge of the genomic consequences of recent rapid population declines of wild organisms is limited. Do populations experiencing recent rapid population decline have the same genomic status as wild populations that experience long-term declines? Yellow-breasted Bunting (Emberiza aureola) is a critically endangered species that has been experiencing a recent rapid population decline. To answer the question, we assembled and annotated the whole genome of Yellow-breasted Bunting. Furthermore, we found high genetic diversity, low linkage disequilibrium, and low proportion of long runs of homozygosity in Yellow-breasted Bunting, suggesting that the populations following recent rapid declines have different genomic statuses from the population that experienced long-term population decline.

Current breeding distributions and predicted range shifts under climate change in two subspecies of Black-tailed Godwits in Asia.

Habitat loss and shifts associated with climate change threaten global biodiversity, with impacts likely to be most pronounced at high latitudes. With the disappearance of the tundra breeding habitats, migratory shorebirds that breed at these high latitudes are likely to be even more vulnerable to climate change than those in temperate regions. We examined this idea using new distributional information on two subspecies of Black-tailed Godwits Limosa limosa in Asia: the northerly, bog-breeding L. l. bohaii and the more southerly, steppe-breeding L. l. melanuroides. Based on breeding locations of tagged and molecularly assayed birds, we modelled the current breeding distributions of the two subspecies with species distribution models, tested those models for robustness and then used them to predict climatically suitable breeding ranges in 2070 according to bioclimatic variables and different climate change scenarios. Our models were robust and showed that climate change is expected to push bohaii into the northern rim of the Eurasian continent. Melanuroides is also expected to shift northward, stopping in the Yablonovyy and Stanovoy Ranges, and breeding elevation is expected to increase. Climatically suitable breeding habitat ranges would shrink to 16% and 11% of the currently estimated ranges of bohaii and melanuroides, respectively. Overall, this study provides the first predictions for the future distributions of two little-known Black-tailed Godwit subspecies and highlights the importance of factoring in shifts in bird distribution when designing climate-proof conservation strategies.

Artificial shelters provide suitable thermal habitat for a cold-blooded animal.

Human activities such as urbanization often has negative affects wildlife. However, urbanization can also be beneficial to some animals by providing suitable microhabitats. To test the impact of urbanization on cold-blooded animals, we first conducted a snake survey at a national nature reserve (Xianghai natural reserve) and an adjacent tourist bird park (Red-crowned Crane Park). We show high presence of Elaphe dione in the tourist park even with high human activities and predator population (the endangered, red-crowned crane, Grus japonensis). We then radio-tracked 20 individuals of E. dione, set seven camera traps, and recorded the temperature of the snakes and artificial structures in Crane Park to document their space use, activity, and thermal preference, respectively. Our results show E. dione preferred to use artificial facilities to shelter from their predators and for thermoregulation. The high number of rats from the camera traps indicate abundant prey items. Overall, E. dione appears to be adapted to modified habitats and may expand population size at the current study site.

Unravelling the processes between phenotypic plasticity and population dynamics in migratory birds.

Populations can rapidly respond to environmental change via adaptive phenotypic plasticity, which can also modify interactions between individuals and their environment, affecting population dynamics. Bird migration is a highly plastic resource-tracking tactic in seasonal environments. However, the link between the population dynamics of migratory birds and migration tactic plasticity is not well-understood. The quality of staging habitats affects individuals' migration timing and energy budgets in the course of migration and can consequently affect individuals' breeding and overwintering performance, and impact population dynamics. Given staging habitats being lost in many parts of the world, our goal is to investigate responses of individual migration tactics and population dynamics in the face of loss of staging habitat and to identify the key processes connecting them. We started by constructing and analysing a general full-annual-cycle individual-based model with a stylized migratory population to generate hypotheses on how changes in the size of staging habitat might drive changes in individual stopover duration and population dynamics. Next, through the interrogation of survey data, we tested these hypotheses by analysing population trends and stopover duration of migratory waterbirds experiencing the loss of staging habitat. Our modelling exercise led to us posing the following hypotheses: the loss of staging habitat generates plasticity in migration tactics, with individuals remaining on the staging habitat for longer to obtain food due to a reduction in per capita food availability. The subsequent increasing population density on the staging habitat has knock-on effects on population dynamics in the breeding and overwintering stage. Our empirical results were consistent with the modelling predictions. Our results demonstrate how environmental change that impacts one energetically costly life-history stage in migratory birds can have population dynamic impacts across the entire annual cycle via phenotypic plasticity.

A pipeline for effectively developing highly polymorphic simple sequence repeats markers based on multi-sample genomic data.

Simple sequence repeats (SSRs) are widely used genetic markers in ecology, evolution, and conservation even in the genomics era, while a general limitation to their application is the difficulty of developing polymorphic SSR markers. Next-generation sequencing (NGS) offers the opportunity for the rapid development of SSRs; however, previous studies developing SSRs using genomic data from only one individual need redundant experiments to test the polymorphisms of SSRs. In this study, we designed a pipeline for the rapid development of polymorphic SSR markers from multi-sample genomic data. We used bioinformatic software to genotype multiple individuals using resequencing data, detected highly polymorphic SSRs prior to experimental validation, significantly improved the efficiency and reduced the experimental effort. The pipeline was successfully applied to a globally threatened species, the brown eared-pheasant (Crossoptilon mantchuricum), which showed very low genomic diversity. The 20 newly developed SSR markers were highly polymorphic, the average number of alleles was much higher than the genomic average. We also evaluated the effect of the number of individuals and sequencing depth on the SSR mining results, and we found that 10 individuals and ~10X sequencing data were enough to obtain a sufficient number of polymorphic SSRs, even for species with low genetic diversity. Furthermore, the genome assembly of NGS data from the optimal number of individuals and sequencing depth can be used as an alternative reference genome if a high-quality genome is not available. Our pipeline provided a paradigm for the application of NGS technology to mining and developing molecular markers for ecological and evolutionary studies.

Sex differences in immune gene expression in the brain of a small shorebird.

Males and females often exhibit differences in behaviour, life histories, and ecology, many of which are typically reflected in their brains. Neuronal protection and maintenance include complex processes led by the microglia, which also interacts with metabolites such as hormones or immune components. Despite increasing interest in sex-specific brain function in laboratory animals, the significance of sex-specific immune activation in the brain of wild animals along with the variables that could affect it is widely lacking. Here, we use the Kentish plover (Charadrius alexandrinus) to study sex differences in expression of immune genes in the brain of adult males and females, in two wild populations breeding in contrasting habitats: a coastal sea-level population and a high-altitude inland population in China. Our analysis yielded 379 genes associated with immune function. We show a significant male-biased immune gene upregulation. Immune gene expression in the brain did not differ in upregulation between the coastal and inland populations. We discuss the role of dosage compensation in our findings and their evolutionary significance mediated by sex-specific survival and neuronal deterioration. Similar expression profiles in the coastal and inland populations suggest comparable genetic control by the microglia and possible similarities in pathogen pressures between habitats. We call for further studies on gene expression of males and females in wild population to understand the implications of immune function for life-histories and demography in natural systems.

The Value of Contrast-Enhanced Ultrasound in Diagnosing Small Renal Cell Carcinoma Subtypes and Angiomyolipoma.

OBJECTIVES: To retrospectively explore the value of contrast-enhanced ultrasound (CEUS) in differentiating small renal cell carcinomas (RCCs) from angiomyolipomas (AMLs), and distinguishing between clear cell RCC (ccRCC), papillary RCC (pRCC), and chromophobe RCC (chRCC). METHODS: A total of 151 patients with small renal masses (110 ccRCCs, 12 pRCCs, 9 chRCCs, and 20 AMLs) were enrolled between August 2016 and October 2019. RESULTS: There were significant differences in terms of enhancement intensity (EI), enhancement homogeneity, perilesional rim-like enhancement (PRE), wash in, and wash out (WO) between RCC and AML (P = .000, .011, .000, .001, .000, respectively). Although there was no significant difference in EI between pRCC and chRCC (P = .272), EI of ccRCC was higher than that of pRCC (P = .000) and chRCC (P = .010). Multivariate regression analysis showed PRE and fast WO were related to RCC (OR = 18.189, 15.141, respectively). Although there were no significant differences in the sensitivity and area under the curve (AUC) between PRE and fast WO (95.0% vs. 95.0%, P = 1.000 and .880 vs. 0.799, P = .123, respectively), the specificity of PRE in predicting RCC was higher than that of fast WO (80.92% vs. 64.89%, P = .011). The sensitivity, specificity, and AUC of the two characteristics combination for differentiating RCC from AML were 95.0%, 90.8%, and 0.920, respectively, and that of EI for differentiating between ccRCC, pRCC, and chRCC were 81.0%, 78.2%, and 0.796, respectively. CONCLUSIONS: CEUS has value in differentiating small RCCs from AMLs and distinguishing ccRCC, a subtype associated with a greater likelihood of malignant behavior from pRCC and chRCC.

Reproductive Success of a Tropical Barn Swallow Hirundo rustica Population Is Lower Than That in Temperate Regions.

Temperate-tropical comparisons of avian life history traits are helpful to understand the different selective pressures placed on birds by different climate zones. Although there have been many comparative studies targeting multiple species in different regions, there are few comparative studies on the reproductive successes of the same species between tropical and temperate regions. In this study, we monitored the breeding activities of the Barn Swallow (Hirundo rustica) simultaneously at a single tropical site and a single temperate site in China, compared the breeding performances of the two populations, and investigated the effects of weather conditions on reproductive success separately. The clutch and brood sizes of the Barn Swallow at the topical site were significantly smaller than those at the temperate site. Furthermore, the breeding success of the Barn Swallow at the tropical site was significantly lower than that at the temperate site. The mean daytime temperature had a negative effect on the clutch size and brood size at both sites; it had a negative effect on nestling survival at the tropical site, but not the temperate site. This study will help us understand the adaptation strategies of widely distributed bird species in different environments, and how climate change will affect birds in different climate zones.

Identifying A New Phylogeographic Population of the Blyth's Tragopan (Tragopan blythii) through Multi-locus Analyses.

Geographically and morphologically distinct populations within a species are frequently the focus of conservation efforts, especially when the populations are evolutionarily significant units. The Blyth's Tragopan (Tragopan blythii) is a globally-threatened species confined to South and Southeast Asia. During our field surveys in western Myanmar, we discovered a distinct group of individuals that differed in their appearance relative to all other populations. We further examined the differences in their DNA sequence using three nuclear introns and three mitochondrial genes through phylogenetic analytical methods. Our results showed the population from Mount Kennedy, Chin Hills formed reciprocal monophyletic groups with the nominate subspecies from Mount Saramati, Sagaing Division. Species delimitation analyses further confirmed this differentiation. Geographical isolation by the intervening lowlands found between high elevation habitats may have been the main cause of their differentiation. Hence, we propose that the Mount Kennedy population be viewed as a distinct evolutionarily significant unit and be given special priority for conservation.

Occurrence and risks of PCDD/Fs and PCBs in three raptors from North China.

Concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) were investigated in muscle samples from common kestrels (Falco tinnunculus), eagle owls (Bubo bubo), and little owls (Athene noctua) collected in Beijing, China. The concentrations of PCDD/Fs were in the ranges of 22.7-5280, 67.5-1610, and 68.4-3180 pg/g lipid weight (lw), while levels of dioxin-like PCBs ranged from 4.91 to 1560, 8.08-294, and 28.2-3540 ng/g lw, in common kestrel, eagle owl, and little owl, respectively. The main PCDD/Fs congener was 2,3,4,7,8-PeCDF, and CB-153 dominated the seven indicator PCBs. PCB levels have shown a decreasing trend in the last decade for the common kestrel, but not for little owl in Beijing, which exhibited higher levels of pollutants and toxic equivalency (TEQ) values than the other two species. Concentrations of PCDD/Fs, dioxin-like PCBs, and indicator PCBs differed between fledgling and adult raptors for certain species. Raptors in this study generally had a higher TEQ than the no-observed-effect level in the literature, indicating significant exposure risks to PCDD/Fs and dioxin-like PCBs in raptors, especially in adult little owls.