Comparisons of microstructure and elemental composition of eggshells among wild plover populations

Reproduction investment is a prominent trade-off in life-history theory and is subject to strong selection pressure.The avian eggshell,as a crucial barrier between the bird embryo and the surrounding environment,undergoes optimization under different environmental selection regimes to ensure the successful development of embryos,which can be linked to local adaptation.Therefore,understanding the variation in eggshell microstructure and composition in wild bird populations living in contrasting ambient environments is of great significance.In this study,we utilized electron microscope ultrastructure measurement and elemental analyses to measure and compare the microstructure and element composition of eggshells from three wild plover populations(Charadrius alexandrinus and C.dealbatus)residing in heterogeneous habitats across varied climatic zones.These populations include the high-altitude Qinghai Lake population,the temperate coastal Tangshan population,and the tropical coastal Zhanjiang population.Our findings revealed that the palisade layer was thinner in the Qinghai Lake population compared to its lowland populations.This difference might be attributed to hypoxia which facilitates the hatching process by allowing chicks to easily break through their shells.Additionally,the variations in the elemental composition of the eggshells among populations well reflected the distribution of element content in different geographical regions.The Qinghai Lake population displayed low zinc and low manganese levels but high calcium levels,while the Zhanjiang population exhibited high zinc,high iron,high manganese,and high phosphorus levels.Furthermore,these variations in elemental composition could also account for the observed microstructural differences among populations.Collectively,we propose that the dissimilarities in eggshell microstructure and elemental composition among populations could be attributed to adaptations to different environmental conditions.Our findings lay the groundwork for future research to explore the mechanisms behind the variations in eggshell characteristics among wild bird populations,and contribute to a broader understanding of biodiversity mechanisms.

Integrative taxonomy of the Russet Bush Warbler Locustella mandelli complex reveals a new species from central China

Background: The Russet Bush Warbler Locustella(previously Bradypterus) mandelli complex occurs in mountains in the eastern Himalayas, southern China, Vietnam, the Philippines, and Indonesia. The taxonomy has been debated,with one(L. seebohmi) to four(L. seebohmi, L. mandelli, L. montis and L. timorensis) species having been recognised.Methods: We used an integrative approach, incorporating analyses of morphology, vocalizations and a molecular marker, to re-evaluate species limits in the L. mandelli complex.Results: We found that central Chinese L. mandelli differed from those from India through northern Southeast Asia to southeast China in plumage, morphometrics and song. All were easily classified by song, and(wing + culmen)/tail ratio overlapped only marginally. Both groups were reciprocally monophyletic in a mitochondrial cytochrome b(cytb) gene tree, with a mean divergence of 1.0 ± 0.2%. They were sympatric and mostly altitudinally segregated in the breeding season in southern Sichuan province. We found that the Mt Victoria(western Myanmar) population differed vocally from other L. mandelli, but no specimens are available. Taiwan Bush Warbler L. alishanensis was sister to the L. mandelli complex, with the most divergent song. Plumage, vocal and cytb evidence supported the distinctness of the south Vietnamese L. mandelli idonea. The Timor Bush Warbler L. timorensis, Javan Bush Warbler L.montis and Benguet Bush Warbler L. seebohmi differed distinctly in plumage, but among-population song variation in L. montis exceeded the differences between some populations of these taxa, and mean pairwise cytb divergences were only 0.5–0.9%. We also found that some L. montis populations differed morphologically.Conclusions: We conclude that the central Chinese population of Russet Bush Warbler represents a new species,which we describe herein, breeding at mid elevations in Sichuan, Shaanxi, Hubei, Hunan and Guizhou provinces.The taxonomic status of the other allopatric populations is less clear. However, as they differ to a degree comparable with that of the sympatric L. mandelli and the new species, we elevate L. idonea to species status, and retain L. seebohmi and L. montis as separate species, the latter with timorensis as a subspecies. Further research should focus on different populations of L. montis and the Mt Victoria population of L. mandelli.

Multiple lines of evidence confirm that the critically endangered Blue-crowned Laughingthrush(Garrulax courtoisi)is an independent species

The taxonomy of the Blue-crowned Laughingthrush(Garrulax courtoisi)and its relationship with the Yellowthroated Laughingthrush(G.galbanus)and G.c.simaoensis,a range-restricted subspecies in China,has not been fully elucidated.So the taxonomic status and system evolution of the three taxa G.courtoisi,G.galbanus and G.c.simaoensis need to be reclarified.Two gene sequences myoglobin(MYO)and the mitochondrial cytochrome coxidase subunit I(COI)were combined to investigate the phylogenetic relationships among courtoisi,simaoensis and galbanus,genetic data,combining with morphological,ecological and acoustic data were used to comb out the classification status and divergence level of the three taxa.Significant genetic and morphological differentiations(body size and plumage coloration)were detected between courtoisi and galbanus.However,no notable and reliable differences between the courtoisi and simaoensis were detected.The courtoisi,simaoensis and galbanus are clearly isolated in geographical distribution as a result of differing altitudes,climate conditions and habitats.The courtoisi has characteristic preference for nest location compared with galbanus.In addition,the results of song analysis also indicated that there are differences in maximum frequency between courtoisi and galbanus.G.courtoisi was confirmed to be an independent species based on genetic,morphological,geographical,ecological and vocal characteristics,and the validity of simaoensis as a subspecies still need more evidence.This study further confirmed the high conservation value of Blue-crowned Laughingthrush.In addition,due to the genetic differences between Simao and Wuyuan populations,this should be fully considered in future protection strategies.

Taxonomy of the White-browed Shortwing(Brachypteryx montana)complex on mainland Asia and Taiwan:an integrative approach supports recognition of three instead of one species

Background: The White-browed Shortwing(Brachypteryx montana) is widespread from the central Himalayas to the southeast Chinese mainland and the island of Taiwan, the Philippines and Indonesia. Multiple subspecies are recognised, and several of these have recently been suggested to be treated as separate species based on differences in morphology and songs.Methods: We here analyse plumage, morphometrics, songs, two mitochondrial and two nuclear markers, and geographical distributions of the two mainland Asian taxa B. m. cruralis and B. m. sinensis and the Taiwan Residents B. m. goodfellowi.Results: We conclude that these differ congruently in morphology, songs and DNA. Male B. m. goodfellowi is the most divergent in plumage(sexually monomorphic, unlike the two others; male similar to female), and B. m. cruralis and B. m. sinensis differ in male plumage maturation. The song of B. m. cruralis is strongly divergent from the others, whereas the songs of B. m. sinensis and B. m. goodfellowi are more similar to each other. Brachypteryx m. sinensis and B. m. goodfellowi are sisters, with an estimated divergence time 4.1 million years ago(mya; 95% highest posterior distribution [HPD] 2.8–5.5 mya), and B. m. cruralis separated from these two 5.8 mya(95% HPD 4.1–7.5 mya). We also report notable range extensions of B. m. sinensis as well as sympatry between this taxon and B. m. cruralis in Sichuan Province, China. Brachypteryx m. montana from Java is found to be more closely related to Lesser Shortwing(B. leucophris) and Rusty-bellied Shortwing(B. hyperythra) than to the mainland Asian and Taiwan Residents taxa.Conclusion: Our data support a recent proposal to treat the three mainland Asian and Taiwan Residents taxa as three species, separate from B. montana sensu stricto: B. cruralis(central Himalayas to south central China and south Vietnam), B. sinensis(north central to southeastern part of China's Mainland) and B. goodfellowi(Taiwan Island).

Identification of vocal individuality in male cuckoos using different analytical techniques

Background: Individuality in vocalizations may provide an effective tool for surveying populations of the Common Cuckoo(Cuculus canorus) but there remains few data on which technique to use to identify individuality. In this research, we compared the within-and between-individual variation in cuckoo calls using two different analytical methods, and discuss the feasibility of using call individuality to count male cuckoos within a population.Methods: We recorded vocalization from 13 males, and measured 15 spectro-temporal variables for each call. The majority of these call variables(n = 12) have greater variation between individuals than within individual. We first calculated the similarity(Pearson's R) for each paired calls in order to find a threshold that could distinguish calls emitted from the same or different males, and then counted the number of males based on this distinction. Second, we used the more widely accepted technique of discriminant function analysis(DFA) to identify individual male cuckoos, and compared the correct rate of classifying individuals between the two analytical methods.Results: Similarity of paired calls from the same male was significantly higher than from different males. Under a relatively broad threshold interval, we achieved a high(>90%) correct rate to distinguish calls and an accurate estimate of male numbers. Based on banded males(n = 3), we found the similarity of paired calls from different days was lower when compared with paired calls from the same day, but this change did not obscure individual identification, as similarity values of paired calls from different days were still larger than the threshold used to distinguish calls from the same or different males. DFA also yielded a high rate(91.9%) of correct classification of individuals.Conclusions: Our study suggests that identifying individual vocalizations can form the basis of an appropriate survey method for counting male cuckoos within a population, provided the performance of different analytical techniques are compared.

Comparing post-release survival and habitat use by captive-bred Cabot's Tragopan(Tragopan caboti) in an experimental test of soft-release reintroduction strategies

Background: Restoring a viable population by reintroduction is the ultimate goal of a large number of ex situ conservation projects for endangered animals. However, many reintroductions fail to establish a population in the wild, partly because released animals cannot acclimate to the native environment of the release site, resulting in very low survival rates. Acclimation training is a technique to resolve this problem, although it does not have positive results in all species. We tested whether acclimation training and soft-release could improve the reintroduction success for captive-bred Cabot's Tragopan(Tragopan caboti), an endangered pheasant in southern China.Methods: Reintroduction of captive-bred Cabot's Tragopan was carried out in the Taoyuandong National Nature Reserve, China from 2010 to 2011. We built a soft-release enclosure for acclimation training in the typical montane habitat of this pheasant. Nine birds were acclimated to the environment of this release site in this cage for more than 50 days before release("trained birds"), while 11 birds remained only in the cage for 3 days prior to release("untrained birds"). Released birds were tagged with a collar radio-transmitter.Results: Post-release monitoring revealed that the survival rate of trained birds was higher than that of untrained birds after 50 days(trained: 85.7%; untrained: 20.0%). Cox regression analysis showed that there was a significant difference in the mortality rates between the trained and untrained birds. In addition, a survey of the habitat of the experimental and the control groups showed significant differences in habitat selection between the groups.Conclusion: Our study suggests that pre-release acclimatization training is an important factor that can lead to improved survival and habitat selection of captive-bred reintroduced tragopans.

Long-lived birds suffer less from oxidative stress

Background: Oxidative stress, caused by an imbalance between reactive oxygen species and antioxidants, is thought to be an important intrinsic mechanism for aging. Ecologists have tested this hypothesis in birds, although the evidence supporting the link between oxidative stress and lifespan has so far been ambiguous. Two previous studies based on a wide range of different free-living bird species provided contradictory findings: antioxidants were negatively associated with survival rate in one study, but positively associated with longevity in another.Methods: In this study, we identified possible shortcomings in previous research, and then used the comparative methods to test whether long-lived birds experience less oxidative stress reflected by four blood redox state markers(total antioxidant status, uric acid, total glutathione, malondialdehyde) based on data for 78 free-living species.Results: Relatively long-lived bird species had high levels of antioxidants(total antioxidant status, total glutathione) and low levels of reactive oxygen species(malondialdehyde). These associations were independent of statistical control for any effects of body mass, sampling effort and similarity among taxa due to common phylogenetic descent.Conclusions: The direction of these associations is consistent with the oxidative stress theory of aging.

Reliability of the Brownish-flanked Bush Warbler's soft song in male-male conflict

Background: Soft song is a low-amplitude song produced by many birds. Recent studies have confirmed that soft song is an aggressive signal. For example, the Brownish-flanked Bush Warblers Cettia fortipes use soft song in male-male conflicts, particularly prior to attacks. Although stable signaling systems require that signals be honest on average,models predict that cheating is an acceptable strategy for some individuals or in some contexts.Methods: This study aimed to test the reliability of soft song as an aggressive signal in the brownish-flanked bush warbler. We used mounted specimens accompanied by broadcast songs or soft songs to simulate a male attempting to invade an existing territory.Results: We found the mounted specimen that coupled playback of soft songs suffered more and quicker attacks from the territory owner and that the relationship between soft song and subsequent attack in the territory owner was far from perfect. We observed territory owners that both over-signaled(i.e., produced soft song but did not attack) and under-signaled(i.e., attacked without producing soft song). Under-signaling territory owners were relatively more commonly than were over-signaling territory owners, particularly in simulated intrusion that coupled playback of soft song with a mount specimen.Conclusions: We discuss the cost of producing soft song and the potential benefit of the unreliable use of soft song and propose a new hypothesis for under-signaling with soft song; i.e., under-signaling territory owners might benefit from taking the initiative in fights.

Alpha声学指数效应的meta分析

通过声学指数量化声音的特征反映生物的组成和生境信息,是一种高效率、低干扰的监测方式。该研究领域在近十多年来得到了快速的发展,不断有新的声学指数被提出,同时也有大量的实证研究。声学指数可分为反映录音内信息的alpha声学指数和比较不同录音之间差异的beta声学指数,其中alpha声学指数的实证研究较多。本文在汇总已有研究数据的基础上进行meta分析,关注alpha声学指数与动物多样性、生境质量、动物活跃性之间关联的方向和程度。基于文献调研,本文对8个常用的声学指数进行了总结分析:声学复杂度指数(acoustic complexity index,ACI)、声学熵指数(acoustic entropy index,H)、生物声学指数(bioacoustic index,BI)、标准化声景差异指数(normalized difference soundscape index,NDSI)、声学多样性指数(acoustic diversity index,ADI)、声学均匀度指数(acoustic evenness index,AEI)、声学丰富度指数(acoustic richness index,AR)和频峰数(number of peaks,NP)。其中,ACI是使用频次最高的声学指数,与动物多样性、生境质量和动物活跃性均存在正相关的关系。ACI与陆地动物活跃性之间的联系最为密切,总效应量的均值达到0.53。然而,其他声学指数与动物多样性、生境质量和动物活跃性之间的关联程度普遍不高,平均解释力不足10%。此外,AEI与生境质量呈显著负相关的关系(相关系数的均值为–0.18,符号检验P=0.001),是本研究发现的唯一显著负相关的联系。本研究结果可为常用alpha声学指数的选用提供参考依据。

Comparative urbanization of birds in China and Europe based on birds associated with trees

Urbanization effects on living organisms are spatially heterogeneous.Here we quantified the abundance of birds per tree in forested urban and rural habitats for 85,829 trees mainly in China and Europe.A population model was based on the assumption that:1)birds have a normally distributed habitat preference;2)an increase in population size linked to the habitat preference;3)a population size dependent on the habitat preference;and 4)the removal of a certain fraction of individuals giving rise to extinction.We tested for large-scale differences in the impact of urbanization on the frequency distribution of the difference in abundance between urban and rural habitats in China and parts of Europe.The difference in the frequency distribution of urban population density of birds in trees minus rural population density of birds in trees in China and Europe was statistically significant suggesting that the abundance of birds differed between trees in urban and rural habitats,but more so in China than in Europe.We hypothesize that more pronounced differences in China than in Europe may have arisen due to the Four Pests Campaign in 1958-1962 that resulted in death of hundreds of millions of birds(mainly tree sparrows Passer monfanus,but also numerous other less common species that were starting to become urbanized around 1960).Species that were less common in 1960 could not sustain reductions in population size in urban areas and hence these species are still rare or absent in urban areas today 60 years later.