砂土中桥梁高桩承台基础的抗震延性能力参数分析

尽管现行的各国抗震规范对桩基础优先按照能力保护构件进行设计,但以往震害和相关分析表明,桩基础进入非线性对于桥梁的抗震性能并非一定不利。基于此出发点,本文采用Pushover方法对2×3高桩承台基础的延性能力进行了参数分析,探究其延性抗震的潜力。数值模型通过某高桩承台基础的拟静力试验进行了验证。参数分析考虑了桩基础、上部结构和土体三方面参数变化的影响,包括桩径、配筋率、配箍率、恒载轴压比、承台底附加弯矩、自由段长度和土体相对密实度。提出了基于不同性能状态的高桩承台基础延性能力指标:"易修位移延性系数"和"极限位移延性系数",揭示了指标随各参数的变化规律;结果表明,易修、极限位移延性系数基本符合对数正态分布,中位值分别为2.66、3.82,延性能力可观;另外,建立了位移延性系数和截面曲率延性系数的定量关系。

Oral disease is linked to low nestling condition and brood size in a raptor species living in a highly modified environment

Anthropogenic stressors can favor the occurrence of noninfectious disease that can be worsened by the impact of opportunistic pathogens,making the epizootiology of environmental diseases difficult to unravel.The incidence and impact of oral lesions in nestlings of a facultative scavenger species,the black kite Milvus migrans,were examined over seven breeding seasons in the highly degraded environment close to Madrid,Spain.We found an overall prevalence of 31%of nestlings with oral lesions,with no clear spatial pattern in nests with affected and unaffected individuals.The occurrence and number of oral lesions were negatively associated with nestling body condition and brood size.Broods,where all siblings had oral lesions,were smaller than those where some or all siblings were apparently healthy,suggesting that oral disease could be causing nestling mortality and,consequently,brood size reduction.In turn,nestling body condition was negatively affected by lesion occurrence,brood size,and laying date.Although these relationships were bidirectional,piecewise structural equation modeling analyses showed a greater negative effect of body condition on lesion occurrence than vice versa,indicating that nestlings in poorer body condition were more likely to develop oral lesions(which could contribute to aggravate their state of deterioration)than those in better condition.Nestlings from small broods were also more likely to have oral disease(directly or indirectly through their lower body condition)than nestlings from large broods.Nestlings that hatched last in the broods showed greater development stress than those that hatched first.Anthropogenic stressors could trigger poor body condition,and contribute to microbiota dysbiosis-related diseases.Although further research is needed to determine the consequences for the long-term fitness of individuals,actions should be taken to mitigate adverse conditions that may favor the appearance of environmental diseases associatedwithperi-urbanareas,giventheirrapidexpansion overnatural areas.

Nestling sex ratio is unaffected by individual and population traits in the griffon vulture

Variation in offspring sex ratios is a central topic in animal demography and population dynamics.Most studies have focused on bird species with marked sexual dimorphism and multiple-nestling broods,where the offspring sex ratio is often biased due to different individual or environmental variables.However,biases in offspring sex ratios have been far less investigated in monomorphic and single-egg laying species,and few studies have evaluated long-term and large-scale variations in the sex ratio of nestling vultures.Here,we explore individual and environmental factors potentially affecting the secondary sex ratio of the monomorphic griffon vulture Gyps fulvus.We used information collected at three breeding nuclei from central Spain over a 30-year period(1990–2020)to analyse the effects of nestling age,parental age,breeding phenology,conspecific density,population reproductive parameters,and spatial and temporal variability on nestling sex.Sex ratio did not differ from parity either at the population or the nuclei level.No significant between-year differences were detected,even under highly changing conditions of food availability associated with the mad-cow crisis.We found that tree nesting breeders tend to have more sons than daughters,but as this nesting behavior is rare and we consequently have a small sample size,this issue would require additional examination.Whereas further research is needed to assess the potential effect of breeder identity on nestling sex ratio,this study contributes to understanding the basic ecology and population dynamics of Griffon Vultures,a long-lived species with deferred maturity and low fecundity,whose minor deviations in the offspring sex ratio might imply major changes at the population level.

Interspecific differences in plasma carotenoid profiles in nestlings of three sympatric vulture species

Carotenoids are diet-based micronutrients important in health and coloration signaling.Related species with similar diets can differ in the kinds and levels of circulating carotenoids,which suggests specific physiological mechanisms to efficiently utilize these micronutrients,regardless of their availability.We explored whether diet and parental provisioning of unusual sources of carotenoids(fresh vegetal matter and vertebrate feces)can explain the occurrence and concentrations of carotenoids in the cinereous vulture Aegypius monachus,griffon vulture Gyps fulvus,and Egyptian vulture Neophron percnopterus nestlings,even when these pigments appear to not be deposited in their integumentary system.A greater diversity of wild prey in diet could be behind the profile of higher concentrations of carotenoids in the Egyptian vulture,the species with carotenoid-dependent coloration during adulthood,while differences in diet composition between cinereous and griffon vultures do not translate to different carotenoid profiles.The carotenoid profile appears to not be related to the ingestion of unusual matter rich in these compounds,although the infrequent occurrence of lycopene and unidentified y-carotene-like compounds suggest that these vultures may be exploiting vegetal matter that left no identifiable unconsumed remains in the nest of Egyptian vultures.The consumption of green plant material by griffon vultures does not result in especially high levels of carotenoids when compared to the carotenoids found in cinereous vultures,which do not consume green plant material.Ungulate feces were not provisioned to Egyptian vulture nestlings,despite the fact they contain carotenoids that adults need for appropriate coloration.Overall,this study indicates that diet differences alone appear insufficient to explain contrasting inter.specific carotenoid profiles,especially since all types of food consumed are considered to be poor in carotenoids,except vegetable matter.We suggest that nestling Egyptian vultures are comparatively efficient in uptaking carotenoids present in low concentrations in food when these compounds are not deposited in their integument,which suggests allocation to other functions.

Nesting innovations allow population growth in an invasive population of rose-ringed parakeets

Certain traits of recipient environments,such as the availability of limiting resources,strongly determine the establishment success and spread of non-native species.These limitations may be overcome through behavioral plasticity,allowing them to exploit alternative resources.Here,we show how a secondary cavity nester bird,the rose-ringed parakeet Psittacula krameri,innovates its nesting behavior as a response to the shortage of tree cavities for nesting in its invasive range in Tenerife(Canary Islands).We observed that some breeding pairs excavated their own nest cavities in palms,thus becoming primary cavity nester,whereas others occupied nests built with wood sticks by another invasive species,the monk parakeet Myiopsitta monachus.The use of these novel nesting strategies increased the number of breeding pairs by up to 52%over 6 years,contributing to a 128.8%increase of the whole population.Innovative nests were located at greater heights above ground and were more aggregated around conspecifics but did not result in greater breeding success than natural cavities.Occupation of monk parakeet colonies by rose-ringed parakeets also benefited the former species through a protective-nesting association against nest predators.Our results show how an invasive species innovate nesting behaviors and increase nest-site availability in the recipient environment,thus facilitating its population growth and invasion process.Potential behavioral innovations in other invasive rose-ringed parakeet populations may be overlooked,and should be considered for effective management plans.

Physiological dormancy broken by endozoochory:Austral parakeets(Enicognathus ferrugineus)as legitimate dispersers of calafate(Berberis microphylla)in the Patagonian Andes

种子由动物内携传播是植物再生和新种群建立的重要过程。具有休眠的种子经过传播者肠道传代作用后可能特别受益。然而,肠道传代作用如何影响具有生理休眠植物的萌发尚不清楚。在本研究中,我们实验性地评估了南鹦哥(Enicognathus ferrugineus)作为小檗属植物(Berberis microphylla)传播者的互惠共生。Berberis microphylla是一种多刺的灌木,栖息在南美洲温带森林的下层,其种子具有深度生理休眠的特性。本研究通过四种处理:(1)种子消化处理,(2)粪便提取物消化处理,(3)果实种子完整处理和(4)包含果肉果实种子完整处理,测定了从粪便和完整果实中提取的B.microphylla种子的发芽成功率和活力。研究结果表明,大约65%的南鹦哥的粪便中含有B.micro phylla种子。不同处理的种子存活率无显著差异。然而,消化后的种子萌发率显著高于完整果实种子,而粪便和果肉提取物处理之间没有差异。粪便和果肉都没有为种子提供任何提高发芽能力的生态优势,但在萌发时间上确实造成了一些劣势。由于持续降雨和巴塔哥尼亚安第斯山脉春季融雪带来的严重冲刷,种子附近的粪便在雪下几个月后就会完全缺失。消化种子较高的发芽能力和较快的发芽速度验证了南鹦哥和B.microphylla之间具有合理互惠共生的假设。因为消化和非消化种子发芽能力的差异,我们假设通过传播者的肠道传代作用可能打破种子的生理休眠。我们的研究结果强调了在具有高度季节性的环境下,具有生理休眠的植物物种中与动物内携传播的相关作用。