摘要: The imbalanced allocation of maternal resources to eggs and nestlings may significantly impact the phenotype and fitness of offspring. Moreover, anthropogenic metal pollution has been reported to exert adverse effects on avian offspring. Therefore, we herein evaluated the relationships among offspring characteristics, asymmetric sibling rivalry, and the resulting offspring phenotype in a small passerine bird, Tree Sparrow（Passer montanus）, at a polluted site（Baiyin, BY） and a relatively unpolluted site（Liujiaxia, LJX）. By initiating incubation before the completion of clutch, asymmetric sibling rivalry might create a core and marginal offspring within the brood. In this study, lower egg mass, fewer core offspring, and more marginal offspring were found at the polluted site. Although eggshell speckling and coloration were relatively similar between the two sites, higher eggshell spotting coverage ratio and lower eggshell lightness（L^*） and hue（h^°） were observed in core eggs than in marginal eggs at the unpolluted site. The clutch size had a positive relationship with egg mass at the polluted site and with brood size at hatching at the unpolluted site. The differences in egg measurements across the laying orders in the samples were relatively large for larger clutch sizes. The core and marginal egg masses had a significant positive effect on the size of early core nestlings and late marginal nestlings at the unpolluted site. Fledgling rate was significantly positively related to the incubation period and nestling period, while negative relationship with mean spotting coverage ratio was found at the polluted site. Marginal nestlings at the polluted site showed a higher mortality rate. Overall, although asymmetric sibling competition strongly determines the variation of marginal offspring size, the effect is less dramatic in metal-polluted environments, providing some respite to wild birds that survive pollution-induced stress.

摘要: During the non-breeding season(September–April), Black-tailed Godwits(Limosa limosa) are commonly seen in coastal and inland wetlands of the Ganges-Brahmaputra-Meghna Delta in Bangladesh. We hypothesize that the Ganges-Brahmaputra-Meghna Delta, at the overlap between the Central Asian and East Asian–Australasian flyways, may host three subspecies that breed in disjunct areas of temperate and northern Asia: L. l. limosa, L. l. melanuroides, and L. l. bohaii. We used mitochondrial DNA(mt DNA) haplotype network and biometric analysis to determine subspecies in captured individuals, and deployed GPS–GSM transmitters to verify breeding areas of individuals with subspecies assignments. To test for differential habitat preferences, we sampled birds at two ecologically distinct habitats known to host the largest concentrations of non-breeding Black-tailed Godwits in Bangladesh: Nijhum Dweep National Park, a tidal coastal habitat with brackish water on the south-central coast, and Tanguar Haor(‘backmarsh'), a seasonal freshwater floodplain in the north. During the non-breeding seasons of 2021–2022 and 2022–2023, we sampled and measured 93 Black-tailed Godwits, 54 of which were equipped with GPS–GSM transmitters. Our mt DNA haplotype network analysis confirmed the presence of limosa, melanuroides, and bohaii subspecies at the study sites. Thus, indeed, Black-tailed Godwits subspecies, despite having distinct breeding ranges, exhibit(partially) overlapping non-breeding ranges in Asia. The subspecies composition differed significantly between sites, with limosa and bohaii dominating in Tanguar Haor and melanuroides in Nijhum Dweep. Of the 21 individuals that were tracked to their breeding grounds, 18 migrated to the expected breeding range of their respective subspecies. However, one bird with a limosa haplotype migrated to a known breeding area of bohaii, whereas two birds with melanuroides haplotypes migrated to the supposed breeding range of limosa. Therefore, while ecological factors at both ends of the flyways may shape the morphological and behavioural differences between Black-tailed Godwit subspecies, their delineations and possible gene flow require further studies.

摘要: The transformation of natural habitats into human-modified landscapes has far-reaching consequences for species distribution and abundance. As species adapt to these changing environments, shifts in distribution patterns,niche dynamics, and interspecies interactions may occur, impacting biodiversity at multiple levels and potentially leading to ecosystem imbalances. This study aims to assess the impact of variations in vegetation composition and human disturbance on the distribution of sympatric breeding birds and to determine the extent of niche overlap or differentiation among these species. We conducted field surveys and collected data on bird distribution, vegetation composition, and level of human disturbance in eastern Inner Mongolian grasslands. We focused on the six most frequently co-occurring breeding birds, representing a mix of sparrows, larks, and corvids. Generalized Additive Models revealed varying responses of species occurrence along habitat gradients.Species like the Eurasian Skylark(Alauda arvensis), Mongolian Lark(Melanocorypha mongolica), and Asian Shorttoed Lark(Calandrella cheleensis), increased in larger and more connected habitats, while others, like the Tree Sparrow(Passer montanus), Eurasian Magpie(Pica pica), and Barn Swallow(Hirundo rustica), adapted to more fragmented habitats. Niche analysis indicated habitat generalists tended to occupy larger niches than grassland specialists. Substantial niche overlap was also found among the six co-occurring bird species. Conservation efforts should consider the specific needs of specialist species and strive to maintain or restore critical grassland habitats. Additionally, promoting sustainable agricultural practices that balance the needs of birds and human activities can contribute to the coexistence of generalist and specialist bird species in modified landscapes.

摘要: Wetland degradation is an escalating global challenge with profound impacts on animal diversity, particularly during successional processes. Birds, as highly mobile and environmentally sensitive organisms, serve as effective indicators of ecological change. While previous studies have primarily focused on local community structures and species diversity during a specific season, there is a need to extend the research timeframe and explore broader spatial variations. Additionally, expanding from simple species diversity indices to more multidimensional diversity indices would provide a more comprehensive understanding of wetland health and resilience. To address these gaps, we investigated the effects of wetland degradation on bird diversity across taxonomic, phylogenetic, and functional dimensions in the Zoige Wetland, a plateau meadow wetland biodiversity hotspot. Surveys were conducted during both breeding(summer) and overwintering(winter) seasons across 20 transects in 5 sampling areas, representing 4 degradation levels(pristine, low, medium, and high). Our study recorded a total of 106 bird species from 32 families and 14 orders, revealing distinct seasonal patterns in bird community composition and diversity. Biodiversity indices were significantly higher in pristine and low-degraded wetlands, particularly benefiting waterfowl(Anseriformes, Ciconiiformes) and wading birds(Charadriiformes) in winter, when these areas provided superior food resources and habitat conditions. In contrast, medium and highly degraded wetlands supported increased numbers of terrestrial birds(Passeriformes) and raptors(Accipitriformes, Falconiformes). Seasonal differences in taxonomic, phylogenetic, and functional diversity indices highlighted the contrasting ecological roles of wetlands during breeding and overwintering periods. Furthermore, indicator species analysis revealed key species associated with specific degradation levels and seasons, providing valuable insights into wetland health. This study underscores the importance of spatiotemporal dynamics in understanding avian responses to wetland degradation. By linking seasonal patterns of bird diversity to habitat conditions, our findings contribute to conservation efforts and provide a framework for assessing wetland degradation and its ecological impacts.

摘要: The life-history strategies of organisms are shaped by trade-offs among traits that influence survival, development, reproduction, and ultimately fitness. However, the specific physiological and environmental mechanisms driving population-level variation in phenotypic traits, particularly in relation to migratory adaptations, remain poorly understood. Elevational migration represents an adaptive behavior for mountain birds that offers a unique model to investigate adaptive phenotypes because of the diverse migratory strategies that have been observed within and between species. Flight muscles, as multifunctional organs, exhibit phenotypic variation that aligns with locomotor and thermoregulatory demands. Linking flight muscle phenotypes to migratory strategies can provide insights into inter-and intraspecific variation in migratory adaptations. In this study, we examined spring arrival dates at high-altitude breeding sites for three closely related high-altitude breeding birds in the mountains of Asia: Blue-fronted Redstart(Phoenicurus frontalis), Himalayan Bluetail(Tarsiger rufilatus), and Rufous-gorgeted Flycatcher(Ficedula strophiata). We analyzed relationships between arrival dates and phenotypic traits, including flight muscle physiology, morphology, and internal organ mass, alongside environmental effects on these traits. Our findings indicate that species arriving earlier encountered lower temperatures and exhibited reduced fiber cross-sectional areas coupled with higher fast oxidative glycolytic(FOG) fibers densities. Males displayed pronounced protandry and higher fast glycolytic(FG) fibers densities. Ambient temperature significantly influenced flight muscle phenotypes, highlighting intraspecific variation and the potential plasticity of flight muscle fibers as crucial mechanisms for adapting to migration strategies and environmental conditions. Additionally, this study underscores the potential role of sexual selection in shaping functional phenotypic variation, further advancing our understanding of adaptive strategies in high-altitude migratory birds.

摘要: Food is a critical environmental factor that influences animal survival, especially for small passerines due to their high mass-specific metabolic rates. Basal metabolic rate（BMR） reflects the energy expended by endothermic animals for basic physiological processes and constitutes a major part of their daily energy budget. Some birds have been shown to employ compensatory mechanisms during food shortages, temporarily reducing these selfmaintenance expenditures without using hypothermia. However, the mechanisms of BMR adjustment remain unexplored. In the present study, we assessed the phenotypic variation in basal thermogenesis of Eurasian Tree Sparrows（Passer montanus） by comparing a control group to groups fasted for 6, 12, 18, and 24 h. We focused on the correlation between a reduction in energy metabolism and the alterations of cellular metabolic activities, mitochondrial substrate supply, and changes in serum thyroid hormones during fasting. Our data indicated that fasting groups had significantly lower body mass, BMR, body temperature, and body fat content. Furthermore, fasting groups had significantly lower glycogen levels, mitochondrial state 4 respiration and cytochrome c oxidase（CCO） activity in the liver, and CCO activity in pectoral muscle. The levels of avian uncoupling protein（avUCP） m RNA were significantly reduced, while the levels of myostatin protein in pectoral muscle were significantly increased in the fasting groups. Furthermore, the groups subjected to fasting exhibited significantly lower levels of serum glucose, triglyceride, thyroxine（T₄）, and triiodothyronine（T₃）. Positive correlations were observed between the following pairs of variables: log BMR and log body mass, log body mass and log body fat, log BMR and log state 4 respiration in the liver, log BMR and log CCO activity in the liver and muscle, log BMR and log av-UCP m RNA expression, whereas a negative correlation was observed between log BMR and log myostatin level. In addition, a positive correlation was also detected between log T₃ and each of the following: log BMR, state 4 respiration, and log CCO activity in the liver. Our results suggested that decreased metabolic thermogenesis via down-regulation in cellular aerobic capacity of organs and serum thyroid hormones may be an important survival strategy for fasting Tree Sparrows to reduce energy expenditure.

摘要: The Asian Houbara（Chlamydotis macqueenii）, a vulnerable species, is under significant threat from habitat degradation and anthropogenic pressures in Pakistan's arid landscapes. This study addresses the urgent need for conservation by identifying critical habitats, analyzing the influence of environmental and human factors on species distribution, and projecting future habitat shifts under climate change scenarios. Using the Max Ent model, which achieves a robust predictive accuracy（AUC =0.854）, we mapped current and future habitat suitability under Shared Socioeconomic Pathways（SSP126, SSP370, SSP585） for the years 2040 and 2070. Presently, the suitable habitat extends over 217,082 km², with 52,751 km² classified as highly suitable. Key environmental drivers, identified via the Jackknife test, revealed that annual mean temperature（Bio1） and slope play a dominant role in determining habitat suitability. Projections show significant habitat degradation; however, under SSP585, highly suitable areas are expected to expand by up to 24.92% by 2070. Despite this increase, vast areas remain unsuitable, posing serious risks to population sustainability. Moreover, only 2115 km² of highly suitable habitat currently falls within protected zones, highlighting a critical conservation shortfall. These findings highlight the imperative for immediate, targeted conservation efforts to secure the species' future in Pakistan's desert ecosystems.

摘要: The process of agricultural intensification has led to significant reductions in biodiversity globally. Previous studies examined the role of semi-natural habitats within agroecosystems in supporting bird communities, but few have considered the effects of landscape agricultural intensity on avian conservation potential of seminatural habitats. Here, we disentangle the relative effects of semi-natural habitats within different landscape agricultural intensities on bird community composition in central and eastern Jilin Province, China. We established 322 sampling sites distributed across low, middle, and high landscape agricultural intensities, with 103, 118, and 101 sites respectively. Each sampling site was visited two times in May and June 2023 to test the dissimilarities in bird composition between different landscape agricultural intensities. We found that middleintensity agriculture supported the highest bird diversity in most cases, but low-intensity plays an important role in maintaining insectivorous birds. We used generalized linear models and model selection to assess the relative impacts of semi-natural habitats on bird community along agricultural intensity respectively. Our results showed that the effects of agriculture on bird communities were predominantly influenced by the amount of semi-natural habitats, with effects that differ in accordance with the level of landscape agricultural intensity. Priority should be given to preserve or/and plant these semi-natural habitats in middle-intensity agriculture due to the stronger effect sizes on bird diversity. Specifically, we suggested preserving and promoting woodlands and shrubs in high-intensity agriculture, and simultaneously increasing crop diversity to protect bird diversity in agriculture landscapes in the context of increasing crop intensification globally.

摘要: Nest predation is the leading cause of reproductive failure in birds and a major driving force in the evolution of anti-predation strategies. Current studies on the anti-predation strategies of birds driven by predation pressure have mainly focused on adults. However, the detection and behavioral responses of nestlings toward predation risk require further investigation. In this study, we examined nestling responses to predator sounds. Two species of nestlings, the Reed Parrotbill(Paradoxornis heudei) and Vinous-throated Parrotbill(Sinosuthora webbiana),were exposed to the Sparrowhawk(Accipiter nisus, less common) and Oriental Magpie(Pica serica, more common), which are predator species, the Oriental Turtle Dove(Streptopelia orientalis), which is a commonly found harmless species, and background noise. Our findings revealed that compared to pre-playback of natural begging and playback of background noise and Oriental Turtle Dove sounds, playback of the two predator types decreased the total begging time and total number of calls of the two nestlings species, with the calls of the Sparrowhawk leading to greater suppression of nestling begging behavior than those of the Oriental Magpie.Therefore, our results indicated that these nestlings were able to distinguish predators from harmless species based on auditory cues.

摘要: Inclusive fitness theory posits that altruistic behaviors, which are directed more likely towards relatives, should be favored by natural selection. However, the prevalence of alternative parenting behaviors in offspring selection, including rejecting their own offspring and accepting the offspring of others, remains poorly understood within the context of parental care evolution. In order to investigate the factors that prompt the occurrence of alternative parenting behaviors, we designed a series of experiments in the Azure-winged Magpie(Cyanopica cyanus). By manipulating the nest spatial position or offspring age/number and parent-offspring familiarity, we addressed how parents provided parental care for the manipulated offspring. In the nest resettlement experiment, the probability of parents rejecting their own offspring significantly increased with nest-moving distances while decreased with offspring ages. In the cross-fostering experiments, the probability of parents provisioning unrelated young significantly decreased with the age difference between cross-fostered chicks. In the nest duplication experiments, where parents were given a choice between familiar offspring and unfamiliar unrelated chicks or between unfamiliar offspring and familiar unrelated chicks, the probability of both alternative parenting behaviors was significantly influenced by the time when parental association with their offspring was deprived. We conclude that as offspring phenotypic traits become individualized and fixed at a special developmental stage, parents gradually acquire the capacity for offspring recognition by associating with them. Any factors that disrupt parent–offspring association or introduce unrelated young into the nest prior to this critical timeline can result in the occurrence of alternative parenting behaviors.