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排序方式: 共有218条查询结果,搜索用时 15 毫秒
1.
Wild birds have been identified as a relevant reservoir of Campylobacter spp., therefore, a potential source of infection in humans and domestic animals. The objective of this study was to determine the occurrence of Campylobacter spp. on birds of prey in Spain. In addition, antibiotic resistance profiles of the isolates were evaluated. A total of 689 specimens of 28 raptor species were analyzed, with a resulting individual prevalence of 7.5%. C. jejuni was the most frequently isolated species (88.5%), followed by C. coli and C. lari (3.8% each). The occurrence of Campylobacter was significantly higher (p < 0.05) in nocturnal birds of prey (15.3%), in spring season (12.2%) and in carnivorous species (9.4%). Isolates displayed a remarkable resistance to nalidixic acid (69.9%), ciprofloxacin (69.9%), and tetracycline (55.6%), and a low resistance to streptomycin (6.7%).Our findings highlight the importance of birds of prey as reservoirs of Campylobacter strains and their significant role as carriers of antimicrobial resistance.  相似文献   
2.
Urban green space has various environmental and ecological benefits, and uneven access to such amenities has drawn substantial attention from policy makers in developing sustainable community planning. In this study, we illustrate the spatial distribution of publicly owned and maintained trees in Edmonton, Canada and assess neighborhoods’ heterogeneous tree availability by using the container approach. Through spatial regression models, we further investigate the association of neighborhood public tree availability with socio-economic status (SES). We contribute to the existing literature by taking resident modes of transportation into consideration, in addition to many other commonly examined SES such as household income and ethnicity. Another unique contribution of this study is that we distinguish trees planted on different location types (i.e., boulevard, park, and buffer areas) when exploring the unequal coverage across neighborhoods and among different SES groups. Key results include: (1) a general examination without differentiating location types can lead to misleading results and thus provide inappropriate policy recommendations; (2) resident modes of transportation is a critical factor associated with a neighborhood’s public tree coverage; and (3) there exists evident spatial dependence on public tree availability between neighborhoods. The results from this study provide important information to better understand the issue and to allocate public resource (such as tree coverage) more efficiently and effectively to support sustainable community development.  相似文献   
3.
四川海子山自然保护区鸟类群落结构及多样性   总被引:5,自引:0,他引:5  
应用样线法,调查海子山自然保护区鸟类的组成和群落结构,经调查确认保护区内有鸟类16目48科210种,以留鸟和夏候鸟为主,鸟类区系成分复杂,古北界种类略占优势。根据鸟类栖息地的生境类型,将保护区鸟类划分为5个群落。调查得知,不同群落的优势种、常见种有较大差异;同一群落类型的物种组成、数量、遇见频次的季节差异明显。运用Shannon Weinner指数计算各群落的多样性;采用E=H/Hmax。计算群落中各群落物种的均匀度;用百分率相似性数(index of percent similarity)对各群落做相似性比较。结果表明:保护区内鸟类群落结构与各群落类型内部的空间异质性程度密切相关,群落的空间结构越复杂,则物种多样性就越高;湿地鸟类群落的均匀度指数最高,而高山灌丛鸟类群落的均匀度指数最低;各群落类型百分比相似性指数均较低;鸟类群落结构具有较大差异。  相似文献   
4.
张腾  刘丹  黄明远  文陇英 《安徽农业科学》2014,(33):11734-11737
2013年9月至2013年11月,采用样线法对乐山市五通桥区冠英镇和牛华镇的鸟类资源进行了调查.共记录到冠英镇鸟类28种,隶属5目17科.牛华镇共记录到鸟类35种,隶属6目19科.多样性分析表明,冠英镇农田生境多样性指数最高(2.645),牛华镇水域生境均匀度指数最高(0.949),2个镇的水域生境之间的相似性最低(0.476).冠英镇水域生境鸟类群落不稳定,对岷江河应采取一定的保护措施.  相似文献   
5.
Turloughs are karst wetland ecosystems that are virtually unique to Ireland. Flooding annually in autumn through springs and fissures in the underlying limestone and draining in the springtime, often through the same fissures or swallow-holes, they have been described as ‘temporal ecotones’. Over 300 have been documented. They are priority habitats in the EU Habitats Directive and support a variety of wet grassland and fen type vegetation. Though the vegetation has been recorded and mapped for over 80 turloughs, records for invertebrates are more sporadic. Characteristic species include some aquatic species-often benefiting from the absence of fish-, and many wetland terrestrial species, including carabid beetles that are rare on a European scale. Due to their shallow nature and the full vegetation cover of the basin, turloughs can host internationally significant numbers of visiting winter wildfowl, particularly whooper swans. The variety of plant and invertebrate communities between turloughs is primarily due to different hydrogeomorphological characteristics, but also depends on the range of grazing practices on turloughs. Since these often vary within a turlough basin, this helps maintain within-turlough biodiversity. The main threat to turloughs in the past was drainage, but pollution by nutrients is also now potentially detrimental. However, a more recent and important threat may be the cessation of farming within turloughs. As potentially threatened wetlands of European importance, turloughs require a full inventory of their biodiversity and the factors affecting it. The collation here of all literature concerning turloughs will provide a basis for an integrated approach to future research on turloughs that is essential for a full understanding of these complex ecosystems.  相似文献   
6.
The need to prioritize species based on their perceived endangerment has led to the development of systems for categorizing and assessing their degree of vulnerability. Systems with divergent biological and geographical scopes can result in conflicting lists of high-priority species, potentially confusing conservationists and hampering the efficient allocation of resources. To assess conservation priorities for North American birds, we compare three priority-setting systems; those of the International Union for the Conservation of Nature (IUCN), NatureServe, and Partners in Flight (PIF). We found highest correspondence among the three systems in the highest and lowest categories of the respective systems with lower levels of correspondence in intermediate categories. We suggest that this is because the systems, while using different formulations of criteria, are based on the major factors known to be correlated with extinction risk. The few examples of species listed as a high conservation priority by one group but not one or both of the others appear to be the result of differences in availability or interpretation of data. Better communication and collaboration among those responsible for compiling the priority lists for each system is needed.A primary difference among the systems was the total number of species identified as conservation priorities. IUCN identified the fewest species (47) and PIF the most (157). This difference is the result of differences in geographic and taxonomic scope of each system. However, when considered as the percent of the total number of taxa evaluated by each system, all systems identified approximately 20% of species as of conservation concern. To reconcile disparate lists, we urge that conservationists use a hierarchical approach that first considers species that meet thresholds for endangerment under global systems, followed by species considered most vulnerable relative to all continental biota.  相似文献   
7.
Several studies have documented negative effects of persecution by humans on the population dynamics of large birds of prey. Several areas have seen a reduction in persecution in modern times, but the demography of large raptors still makes these birds vulnerable to such effects. In a GIS analysis, utilising data collected during two national censuses of the golden eagle Aquila chrysaetos in Scotland and contemporary data on the distribution of poisoning incidents (a common method of raptor persecution in Scotland), we show that persecution was associated with a reduction in the age of first breeding, territory vacancies, and the use of territories by non-breeding immatures. Persecution was therefore reducing adult survival and distribution and was probably creating ecological traps that attract mobile immatures, increasing subadult mortality in birds that may originate from persecution-free areas. Mapping a form of land management unique to moors managed for red grouse Lagopus lagopus scoticus shooting, where most poisoning occurs, we also show similar associations between golden eagle demography and grouse moor management. As such, persecution may be having a major impact on the golden eagle population of Scotland, since it occurs over a wide area and at least in some areas has continued unchecked over many decades.  相似文献   
8.
We compared breeding bird communities and vegetation characteristics at paired point locations in primary (undisturbed) and mature secondary forest (70-100 years old) sites in Great Smoky Mountains National Park, USA to understand how sites logged prior to creation of the park compare to undisturbed sites following 70 years of protection from human disturbance. We found that bird and vegetation communities are currently similar, but retain some differences in species composition. Rank abundance curves for primary and secondary forest bird communities showed very similar patterns of species dominance. Species composition was also similar on the two sites which shared 24 of the 25 most frequently recorded species. Nonetheless, comparisons of density estimates derived from distance sampling showed three bird species were more abundant on primary forest sites and that one bird species was significantly more abundant on secondary forest sites. Notably, comparisons based on raw counts (unadjusted for potential differences in detectability) produced somewhat different results. Analyses of vegetation samples for the paired sites also showed relative similarity, but with some differences between primary and secondary forests. Primary forest sites had more large trees (trees greater than 50 cm diameter at breast height) and late successional species. Primary forest sites had a denser tall shrub layer while secondary forest sites had a denser canopy layer. Nonetheless, tree species richness, basal area of live trees and number of standing snags did not differ between primary and secondary forest sites. Results indicate that breeding bird communities on sites within the park that were logged commercially 70 years ago are currently quite similar to bird communities on sites with no history of human disturbance. Similarities between the bird communities on previously disturbed and undisturbed sites in Great Smoky Mountains National Park may exceed those on more fragmented landscapes because large patches of primary forest, adjacent to commercially logged sites, remained in the park when it was established in 1935. These patches of primary forest may have served as source areas for commercially logged sites.  相似文献   
9.
The aggregation of individuals into foraging flocks is one behavioural trait that, if disrupted, can cause the Allee effect, which is a slowing in population growth at low density or small population size, and this can greatly increase the risk of extinction. Here, I describe intraspecific flocking behaviour of a colour-banded population of speckled warblers, Chthonicola sagittata, a species that has declined across a large part of its range in the fragmented temperate woodlands of Australia. I make predictions about the context in which the Allee effect might be expressed and the consequences for the viability of populations living in small habitat remnants. Speckled warblers lived in discrete, stable social groups throughout winter, the nucleus of which was the residents from one or more adjacent breeding territories. The timing and mode of flock formation and the size of flocks varied between two winters, apparently in response to the severity of conditions; thus flocking probably facilitates increased foraging efficiency and predator detection, potentially leading to increased survival in harsh conditions. Because flock territories were up to 30 ha each, and larger territories are likely, birds living in remnants smaller than 40 ha may suffer increased mortality if there are too few birds available to form flocks of an appropriate size to facilitate the benefits of grouping when conditions are most extreme. Further, in small remnants where survival is reduced, dominance behaviour and male-male competition may act to compound the Allee effect by reducing reproductive success. Regardless of these predictions, speckled warbler populations may only be viable in remnants that are large enough to support multiple flocks, to enable rapid recruitment to breeding vacancies and thus provide adequate numbers of birds for flocking.  相似文献   
10.
Small aspen stands are disappearing from the landscape in the Southwest, so it is important to understand their contribution to the avian community. We sampled birds in 53 small, isolated aspen stands and 53 paired plots within the ponderosa pine forest in northern Arizona, during the 1996 and 1997 breeding seasons. Bird species richness and abundance were higher in aspen than in pine. However, bird species richness and abundance did not vary with size of the aspen patch or isolation index. In addition, direct ordination of species distributions with habitat factors suggested no distinct avian communities. This suggests that aspen stands do not harbor separate populations, but rather are locations where the regional avifauna reaches high local density and richness and may be crucial to birds in years of resource scarcity. Thus it is important for avian conservation to maintain many aspen stands across the landscape, encompassing a diversity of vegetation structure and composition.  相似文献   
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