Multifunctional use of a natural resource on farmland: wild pheasant (Phasianus colchicus) management and the conservation of farmland passerines

Current rural development policy encourages farmers to adopt multifunctional use of farmland. Non-agricultural resources such as wildlife provide a focus for recreational activities such as shooting and bird watching. This paper assesses the potential contribution of wild pheasant (Phasianus colchicus) management for shooting to the conservation of farmland passerines. Bird numbers were monitored over a 7-year period on farmland in Leicestershire (England), in relation to the introduction of a game management system. Passerines were used as the indicator group as they are an official quality of life indicator, and include species that are the subject of government biodiversity action plans. Following introduction of the game management package, there was little change in species diversity at the farm scale, but species experiencing population declines nationally showed significant increases in numbers. The management of wild pheasants for shooting may therefore have considerable potential for the conservation of nationally declining farmland birds and for recreational activities such as bird watching.     

Landscape-dependent use of a seed-rich habitat by farmland passerines: relative importance of game cover crops in a grassland versus an arable region of Scotland

Capsule Game cover crops in a pastoral region of southwest Scotland supported passerines at more than twice the density found in similar crops in an arable region.

Aims To investigate the use of seed-rich habitats (game cover crops) by farmland passerines in the agricultural grasslands of southwest Scotland relative to the arable east.

Methods Birds were counted in game cover crops and conventional crops on nine farms in Dumfries and Galloway, and Ayrshire, during the winters of 2003/04 and 2004/05. Similar data from eastern Scotland were re-analysed to compare the relative use of the two crop types in the contrasting regions.

Results Passerine densities in game cover crops in southwest Scotland were two orders of magnitude greater than in conventional crops. Furthermore, densities within grassland game cover crops were more than double those in arable areas and densities in grassland conventional crops were just 14% of those in equivalent arable habitats.

Conclusion The significantly greater difference between passerine densities in game cover crops and conventional crops in a grassland versus an arable region of Scotland could not be explained by differences in the bird communities, crop types, boundary habitats, weather, observer effects or survey methods used. We suggest that game cover crops may be more attractive in grassland regions because alternative food sources are rarer than in arable regions.     

Habitat associations and breeding success of yellowhammers on lowland farmland

1.  Yellowhammers began to decline on British lowland farmland in the late 1980s and losses are presently 10% per year. This study examined variation in the habitat selection and breeding success of yellowhammers, allowing an evaluation of whether Britain's yellowhammer decline might have been caused by recent changes in agriculture.
2.  Yellowhammer territories were associated with hedgerows, vegetated ditches and wide uncultivated grassy margins around fields. Pasture and silage leys were avoided. Nests were built among herbaceous vegetation in ditches or in the shrubby vegetation of hedgerows.
3.  Breeding started slightly earlier on organic farms than on intensively managed farms, but no measure of breeding success differed between farm types. Predation was the cause of most (64%) nest failures. A maximum of three breeding attempts (two successful) was observed per pair, with a mean clutch size of 3·3, a Mayfield nest success rate of 0·46, and 2·6 nestlings fledged per successful brood. These data, together with published estimates of adult yellowhammer survival and of post-fledging survival among other passerines, suggest that breeding productivity is too low to maintain a stable population.
4.  The removal of hedgerows or abandonment of hedge management, filling or clearing of ditches, intensification of grassland management and cropping or grazing right up to the field edge, are all likely to have adversely affected yellowhammers on lowland farmland in southern England. Policy reforms that redirect subsidy support to environmentally beneficial management of field margin habitats and retention of winter-feeding sites such as stubbles should assist in restoring populations of breeding yellowhammers on lowland farmland.
5.  Our data expand further the array of farmland bird species for which interactions between agricultural change and population change are increasingly understood.     

Community structure and habitat associations of parrotfishes on Oahu,Hawaii

Despite their ecological importance as bioeroders and their economic importance in commercial, artisanal, and recreational fisheries, there have been relatively few studies on parrotfish (Scaridae) ecology in Hawaii. Belt transects were conducted around the island of Oahu to survey current parrotfish distributions, size structure, species composition and associated habitats. Scarid communities in this heavily fished region are dominated by smaller species and smaller individuals within all species. Specific habitat characteristics such as rugosity, substrate diversity, and percent live coral cover were positively correlated with scarid numerical abundance. Scarids, however, were patchily distributed and were often absent from preferable habitats, suggesting that intense fishing pressure may be an important factor preventing these fish from fully exploiting available habitats. This study is the first thorough, broad-scale investigation of scarid community structure in Hawaii, and provides important information that has management and conservation implications for parrotfish in Hawaii and throughout tropical coral reef ecosystems.     

冀中农区大草蛉(Chrysopa septempunctata)栖息地选择

大草蛉(Chrysopa septempunctata)是华北农区的主要天敌昆虫,研究了作物主要生长季节大草蛉的分布动态及其对栖息地的选择取向,结果表明,(1)大草蛉对栖息生境有较强的选择性,明显趋向于田间杂草地生境;(2)大草蛉在田间草地带上的栖息较为稳定,且受田间草地带宽度的直接影响,宽度1m左右的草地带有更高的大草蛉密度;(3)林带对大草蛉分布显示出积极作用,其效应范围因林带结构不同表现各异;(4)作物生长后期林带逐渐成为大草蛉栖息的重要场所。     

生境破碎化对植物-昆虫及昆虫之间相互关系的影响

生境破碎化对生物多样性和生态系统功能影响是当前国内外生态学家研究的热点问题之一。文章针对生境破碎化的内涵、量度指标进行介绍,着重分析生境破碎化对植物-昆虫关系的影响,包括植物与植食性昆虫的关系、植物与传粉昆虫的关系、种子与种子捕食者的关系,植物及其分解者的关系,还分析生境破碎化对昆虫-昆虫关系的影响,包括昆虫及其拟寄生物的关系、捕食者与猎物的关系。通过对上述方面的阐述,旨在更好地理解生境破碎化对动植物群落相互关系产生的深刻影响,并提出今后研究中应注意的问题和研究热点。     

Performance of an aphid Myzus persicae and its parasitoid Diaeretiella rapae on wild and cultivated Brassicaceae

To determine to what extent wild species related to crops might serve as refuges for insect pests and their natural enemies, we compared the performance of the aphid Myzus persicae and its endoparasitoid Diaeretiella rapae on one cultivar of Brassica napus and Brassica oleracea, two wild species Brassica nigra and Sinapis arvensis, and one cultivar of Solanum lycopersicum. These species differ in traits associated with plant defences that may have an impact on the herbivore and its parasitoid. In contrast to our initial hypothesis, aphid population growth rate was significantly smaller on B. napus than on the other Brassicaceae species. Similarly, the performance of the parasitoid was affected by the host plant on which the aphid was feeding. However, aphid and parasitoid performance was not correlated. Thus, in temporally changing landscapes, pests and natural enemies may utilize crops and wild-related host species with contrasting impacts on their fitness.     

瓢虫种群对棉花-玉米农田景观格局的响应

本文研究了华北棉花-玉米农田景观格局中龟纹瓢虫Propylaea japonica(Thunberg)和异色瓢虫Harmonia axyridis(Pallas)种群动态,发现农田景观格局中作物类型(棉花与玉米)对两种瓢虫种群密度动态有显著的影响,两种天敌瓢虫都趋向在玉米斑块上栖息。两种瓢虫在棉花斑块上呈现出时间分化,其中龟纹瓢虫在棉花种植的前中期种群密度较大,后期较少;而异色瓢虫在棉花前中期种群密度较少,后期较多,表明农田景观中种植玉米有利于增强瓢虫对棉花害虫的控制作用。进一步的研究表明,农田景观系统中玉米斑块所占的面积比对龟纹瓢虫和异色瓢虫种群密度均产生显著影响。这说明在农田景观系统中开展区域性生态调控的时候,需要考虑到各类斑块组合的面积比例,从而有利于增强多种天敌昆虫的协调控害作用。     

Winter and spring abundance of Frankliniella spp. and Thrips tabaci Lindeman (Thysan., Thripidae) on weed host plants in Turkey

Abstract:  The species composition of thrips and abundance of three pestiferous thrips species, Frankliniella occidentalis (Pergande), Thrips tabaci Lindeman and Frankliniella intonsa (Trybom) (Thysan., Thripidae) on weed species during winter and spring time were studied in vegetable production and polycultured areas in the eastern Mediterranean region of Turkey in years 2002 and 2003. Of a total of 61 543 thrips extracted from 8933 samples collected, 77% were adults. F. occidentalis was collected from all of 49 weed species sampled and F. intonsa was detected on 18 plant species between May and June. T. tabaci was collected from 42 of a total of 49 weed species. Immature thrips were extracted from 42 of a total of 49 weed species. Four weed species of a total 35 weed species sampled between April and May in the sampling areas hosted 63% of larvae and approximately 50% of F. occidentalis collected. A total of 23 thrips species was recorded from weeds sampled in this study. F. occidentalis accounted for 83% of a total 47 640 adult thrips collected and followed by low rates of T. tabaci and F. intonsa (9 and 1%, respectively). Melanthrips spp. accounted for 3.54% of total numbers of adult thrips. Flower-inhabiting thrips species and T. tabaci were most abundant on weeds between April and May when the number of weed species in bloom was greatest, then decreased to low levels after May. Most pestiferous thrips on weeds species were collected from vegetable production areas. F. occidentalis was the predominant thrips comprising over 80% in most months in the vegetable grown area. In polycultured area, the composition of adult thrips shifted monthly. While Melanthrips was the more prevailing thrips by rates 53% in February and 81% in March, F. occidentalis was the predominant thrips with 60 to 62% in spring, respectively.     

Cepaea on Salisbury Plain: patterns of variation, landscape history and habitat stability

Patterns of variation in Cepaea nemoralis and C. hortensis on Salisbury Plain are related to its landscape history. Areas of arable or mixed farming, with hedgerows and woods, show patterns of variation with habitat and topography. Areas of downland, until recently heavily grazed by sheep, show area effects. Cepaea populations in these downland areas would have been much rarer, and more isolated when grazing was intense. This pattern is repeated in other parts of southern England, showing that area effects in Cepaea are strongly associated with areas of habitat instability, where Cepaea survived as small and isolated populations until recently. This evidence enhances the plausibility of explanations of area effects involving isolation, founder effect or local selection, and co-adaptation.     

Solving some statistical problems in analyses of experiments on choices of food and on associations with habitat

Statistical tests for non-random associations with components of habitat or different kinds of prey require information about the availability of sub-habitats or types of prey. The data are obtained from sampling (Stage 1 samples). Tests are then constructed using this information to predict what will be the occupancy of habitats or composition of diet under the null hypothesis of random association. Estimates of actual occupancy of habitats or composition of diet are then obtained from Stage 2 sampling and tests are done to compare the observed data from Stage 2 with what was predicted from Stage 1.Estimates from each stage of sampling are subject to sampling error, particularly where small samples are involved. The errors involved in Stage 1 sampling are often ignored, resulting in biases in tests and excessive rejection of null hypotheses (i.e. non-random patterns are claimed when they are not present). Here, accurate tests are developed which take into account both types of error.For animals in patchy habitats, with two or more types of patch, the data from Stages 1 and 2 are used to derive maximal likelihood estimators for the proportions of area occupied by the sub-habitats and the proportions of animals in each sub-habitat. These are then used in χ² tests.For composition of diets, data are more complex, because the consumption of food of each type (on its own) must be estimated in separate experiments or sampling. So, Stage 1 sampling is more difficult and the maximal likelihood estimators described here are more complex. The accurate tests described here give much more realistic answers in that they properly control rates of Type I error, particularly with small samples. The effects of errors in Stage 1 sampling are, however, shown to be important, even for quite large samples. The tests can and should be used in any analyses of non-random association or preference among sub-habitats or types of prey.     

Quantifying the habitat structure and spatial pattern of New Jersey (U.S.A.) salt marshes under different management regimes

Mosquito control measures have resulted in majorstructural alterations of many coastal marshes, withrelatively unknown consequences to larger ecosystemfunctioning. Parallel grid ditching and open marshwater management (OMWM) techniques are purposefullydesigned to alter the hydrological regime and therelative availability and/or characteristics ofstanding water on the marsh surface. With the growingrecognition of the important influence that habitatstructure and the configuration of the marsh-edgeboundary has on nekton utilization of salt marshsystems, the impact of mosquito control managementtechniques on the availability and quality of saltmarsh habitat deserves increased scrutiny. Usingdigital image processing techniques, we completed adetailed mapping effort for a 1800 ha study area inTuckerton, New Jersey to provide a picture ofsubtidal and intertidal habitat availability. Spatialanalysis techniques were used to quantify the relativeamount of habitat types and spatial pattern of theland-water interface under different managementregimes: parallel grid-ditched, OMWM and an unalteredreference. The parallel grid-ditched site had a muchlower incidence of marsh ponds which serve asimportant low tide and over-wintering refuge forcertain species of fish. In comparison, the OMWM sitehad a much greater amount of ponded water habitats.The grid-ditched site had a higher density of marshsurface-to-tidal water interface resulting in a lowermedian distance between the marsh interior and theadjacent tidal channel network. This study serves tobenchmark the habitat structure and spatial pattern ofa highly functioning natural marsh for use as areference site in regional wetland creation orrestoration efforts.     

Modelling the effect of habitat fragmentation on range expansion in a butterfly

There is an increasing need for conservation programmes to make quantitative predictions of biodiversity responses to changed environments. Such predictions will be particularly important to promote species recovery in fragmented landscapes, and to understand and facilitate distribution responses to climate change. Here, we model expansion rates of a test species (a rare butterfly, Hesperia comma) in five landscapes over 18 years (generations), using a metapopulation model (the incidence function model). Expansion rates increased with the area, quality and proximity of habitat patches available for colonization, with predicted expansion rates closely matching observed rates in test landscapes. Habitat fragmentation constrained expansion, but in a predictable way, suggesting that it will prove feasible both to understand variation in expansion rates and to develop conservation programmes to increase rates of range expansion in such species.     

The role of habitat patches on mammalian diversity in cork oak agroforestry systems

Habitat patches, depending on the degree of differentiation from the matrix, can add few or many elements to the species pool of a particular landscape. Their importance to biodiversity is particularly relevant in areas with complex landscapes, where natural, naturalized, or managed habitats are interspersed by small patches of habitat types with very different biophysical characteristics; e.g., fruit orchards and riparian areas. This is the case of the montado landscape, a cork oak agroforestry system that largely covers south-western Portugal. We evaluated whether the high mammalian biodiversity found in this system is, in part, the cumulative result of the species found in the non-matrix habitats. Our results indicate that in areas where there are inclusions of orchards/olive yards and riparian vegetation in the cork oak woodland, a significantly higher number of mammalian species are present. We further detected a positive effect of low human disturbance on mammal diversity. Ultimately, our results can be used by managers to augment their management options, since we show that the inclusion and maintenance of non-matrix habitat patches in cork oak agro-silvo-forestry systems can help to maximize mammal biodiversity without compromising services associated with agriculture and forestry.