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1.
As natural wetlands have disappeared around the world, artificial wetlands have increased. We found interesting differences in waterbird communities of two natural (Bundala Ramsar site) and seven artificial wetlands (irrigation tanks, salt ponds, rice paddies) in south-east Sri Lanka. Eight species exclusively used natural and one species artificial wetlands. Migratory species (shorebirds 64%, terns 47%) dominated species’ richness of natural lagoons, with densities of shorebirds 3-6 times greater than on artificial wetlands. Contrastingly, resident species (dabbling ducks, gallinules) contributed most to the diversity (59%) and density of waterbirds on artificial irrigation tanks. Cattle egrets dominated waterbird density (>70%) of rice paddies. Waterbird communities reflected physical and chemical character of wetlands: natural wetlands were shallow (<2 m) and saline (EC > 1000 msm−1) compared to deep (>2 m) and freshwater (EC < 110 msm−1) artificial wetlands. Artificial inputs of water drained into the natural Embilikala lagoon changing its physico-chemical profile and disrupting the natural seasonal drying. Consequently its waterbird community was similar to artificial irrigation tanks, with shorebird species particularly impacted: densities half that of the other natural lagoon. Artificial salt ponds had similar physico-chemical properties to the natural Bundala lagoon and a similar waterbird community. Even though artificial wetlands supported waterbirds, they were not adequate replacements for loss of natural wetlands, favouring some species. Imposed hydrological stability degraded habitat quality for migratory shorebirds on one of our Ramsar site lagoons.  相似文献   

2.
In 1974, hedgehogs (Erinaceus europaeus) were introduced to the island of South Uist, which forms part of an area holding one of the largest concentrations of breeding shorebirds in Western Europe. By the 1990s these mammals had spread widely and become major predators of shorebird eggs. Breeding shorebirds were surveyed in 1983, when hedgehogs were confined to a small part of South Uist. They were surveyed again in 2000 by when hedgehogs had occupied all of the southern part (South Uist and Benbecula) of the 250 km2 of lowland shorebird nesting habitat for at least 10 years but had not yet colonised large parts of North Uist and adjacent small islands. Between surveys the overall numbers of shorebirds in the hedgehog-free northern zone increased by 9% but in the southern zone, where hedgehogs were present, numbers decreased by 39%. Population changes differed among species, but for all species the population in the hedgehog-free northern zone outperformed that in the southern zone. The most marked differences occurred in northern lapwing (Vanellus vanellus) and common redshank (Tringa totanus), which both showed large declines in the southern zone and moderate to large increases in the northern zone. The north-south differences in population change could not be explained in terms of habitat change and were probably largely driven by hedgehog predation.  相似文献   

3.
Shorebirds are declining worldwide due to loss and degradation of critical breeding and wintering habitats. Some human-modified habitats, particularly salt-pans which are used by shorebirds in many regions of the world, may help substitute for natural habitats lost for a wide range of species during migration. We studied the influence of landscape characteristics on species richness, abundance, and diversity of shorebirds at 20 sites covering most of the Inner Gulf of Thailand, a landscape with a long history of salt farming. Sites with salt-pans present held significantly higher species richness, abundance and diversity of shorebirds. Areas with larger proportions given over to aquaculture tended to have lower species richness, abundance and diversity. Generalized additive models indicated that landscapes with a larger proportion of tidal flats in conjunction with salt-pans were the best predictors of sites with higher species richness, abundance and diversity. Landscape configurations with higher richness, abundance and diversity of shorebirds also tended to be less fragmented and contained slightly larger patches. Shorebirds appeared to use ponds with exposed mud in salt-pans as both roosting sites and supplementary feeding grounds during high tide. Traditional salt-pans therefore proved to contribute significantly to maintenance of overwintering shorebird populations in this landscape and should be investigated elsewhere in Asian coastal zones. Collaboration between researchers, salt farmers and planning authorities as to how best to maintain salt-pans as potential shorebird roost sites such as in the Inner Gulf of Thailand is urgently needed in order to maintain habitat for shorebird populations in critical wintering and staging areas of this flyway.  相似文献   

4.
Intertidal estuaries in north-west Europe provide essential feeding grounds for internationally important numbers of overwintering shorebirds. Monitoring of the food supply available in these intertidal habitats is central to shorebird conservation strategy. In this paper, we describe the methods used to do a baseline survey of the Exe estuary Special Protection Area, south-west England. A grid system of sampling, linked to the Ordnance Survey National Grid, was used to ensure a systematic and repeatable coverage of the whole estuary. Cluster analysis was used to classify sites according to their invertebrate biomass densities. Classification of sites into groups was verified using environmental correlates. Results from these analyses were used to map habitat patches for the whole estuary. We show how, once a baseline survey such as this has been undertaken, monitoring of shorebird food supplies over time should be achievable with reduced sampling effort.  相似文献   

5.
Urbanization and coastal development has dramatically reduced the beach habitat available for foraging shorebirds worldwide. This study tested the general hypothesis that recreational use of shorebird foraging areas adversely affects the foraging behavior of sanderlings Calidris alba. Observations conducted on two central California beaches from January through May and September through December of 1999 showed that number and activity of people significantly reduced the amount of time sanderlings spent foraging. Although the sample size was low, the most significant negative factor was the presence of free running dogs on the beach. The experimentally determined minimal approach distance did not vary significantly with the type of human activities tested. Based on these results, policy recommendations for minimizing the impact of human beach activities on foraging shorebirds include: (1) people maintain a minimum distance of 30 m from areas where shorebirds concentrate and (2) strict enforcement of leash laws.  相似文献   

6.
The extent of a shorebird’s response to a human disturbance depends on the associated energetic or predation risk costs. These costs are influenced by a suite of environmental variables, operating at several temporal and spatial scales. Here, I measured prey availability, distance to forest cover, cloud cover, and wind speed, in addition to human and shorebird densities to examine how human presence affected habitat choice, relative to these environmental variables, at Pachena Beach, British Columbia. In a standardised experiment, I also approached feeding flocks to determine if environmental factors influenced the time take for shorebirds to resume feeding. Binary logistic models suggested that people did not displace shorebirds. Instead, shorebirds were preferentially selecting areas further from forest cover that may have had lower predation risk. The time taken for shorebirds to resume feeding after a human disturbance was greater in the morning and in areas of low prey availability. This suggests that shorebirds respond more to a disturbance when the foraging cost is lower indicating that behavioural responses may not necessarily reflect the potential fitness costs of human disturbance.  相似文献   

7.
The Red List Index (RLI), which uses information from the IUCN Red List to track trends in the projected overall extinction risk of sets of species, is among the indicators adopted by the world’s governments to assess performance under the Convention on Biological Diversity and the United Nations Millennium Development Goals. For greatest impact, such indicators need to be measured and used at a national scale as well as globally. We present the first application of the RLI based on assessments of extinction risk at the national scale using IUCN’s recommended methods, evaluating trends in the status of Australian birds for 1990–2010. We calculated RLIs based on the number of taxa in each Red List category and the number that changed categories between assessments in 1990, 2000 and 2010 as a result of genuine improvement or deterioration in status. A novel comparison between trends at the species and ultrataxon (subspecies or monotypic species) level showed that these were remarkably similar, suggesting that current global RLI trends at the species level may also be a useful surrogate for tracking losses in genetic diversity at this scale, for which no global measures currently exist. The RLI for Australia is declining faster than global rates when migratory shorebirds and seabirds are included, but not when changes resulting from threats in Australia alone are considered. The RLI of oceanic island taxa has declined faster than those on the continent or on continental islands. There were also differences in the performance of different jurisdictions within Australia.  相似文献   

8.
While it is widely understood that local abundance of benthic invertebrates can greatly influence the distribution and abundance of wetland birds, no studies have examined if wetland landscape context can mediate this relationship. We studied the influence of wetland food abundance and landscape context on use of agricultural wetlands by wintering dunlin (Calidris alpina) and killdeer (Charadrius vociferus) in the Willamette Valley of Oregon, USA, over two winters (1999-2000, 2000-2001) of differing rainfall and subsequent habitat distribution. We monitored bird use (frequency of occurrence and abundance) at a sample of wetlands differing in local food abundance (density and biomass) and landscape context [adjacent shorebird habitat (defined as ha of wet habitat with less than 50% vegetative cover and within a 2-km radius) and nearest neighbor distance]. We evaluated predictive models for bird use using linear regression and the Cp criterion to select the most parsimonious model. During the dry winter (2000-2001), dunlin exhibited greater use of sites with higher invertebrate density and biomass but also with more adjacent shorebird habitat and closest to a wetland neighbor. However, neither landscape context nor food abundance were important predictors of dunlin use during the wet winter (1999-2000). Use of sites by killdeer was unrelated to either local food abundance or landscape context measures during both winters. Our findings contribute to a growing recognition of the importance of landscape structure to wetland birds and highlight a number of implications for the spatial planning and enhancement of wetlands using a landscape approach.  相似文献   

9.
The fuelling performance of long-distance migrants at staging areas indicates local conditions and determines the viability of migration routes. Here we present a first case study where long-term fuelling performance was documented along two migration routes with differential population trends. Ruffs (Philomachus pugnax) are shorebirds of inland freshwater wetlands that migrate from the sub-Saharan wintering grounds, via Europe, to the northern Eurasian breeding grounds. Assessments from 2001 to 2008 of fuelling during northward migration at the major western and eastern staging site revealed that daily mass gain rates steeply declined across years in the grasslands for dairy production in Friesland, The Netherlands, and remained constant in the Pripyat floodplains in Belarus, 1500 km further east. Migrants in Friesland decreased from 2001 to 2010 by 66%, amounting to a loss of 21,000 individuals when counts were adjusted for length of stay as determined by resightings. In the same period numbers in Pripyat increased by 12,000. Ruffs individually ringed in Friesland were resighted in subsequent springs at increasingly eastern sites including Pripyat. Our results corroborate published evidence for an eastward redistribution of Arctic breeding ruffs and suggest that the decreasing fuelling rates in the westernmost staging area contribute to this redistribution. The shift implies that responses occur within a single generation. The hypothesis that the choice of route during northward migration may be driven by food availability can now be tested by creating greater areas of wet grasslands in Friesland. When local staging conditions improve we predict that ruffs will make the reverse shift.  相似文献   

10.
An age-structured model of a wandering albatross Diomedea exulans population is developed to stimulate population trends over time, using demographic parameters from the population at Possession Island, Crozets, during 1968–1986. The simulation results portray a population decreasing at a rate of 2·29% per year, which concurs with global population trends. Sensitivity analyses of model parameters indicate that both adult and juvenile mortality are contributing to the decrease. Wandering albatross mortality is presumed to have increased as a result of deaths caused by longline fishing vessels; such deaths are likely to be relatively more frequent among young, naive birds. The model is used to investigate the potential impacts of new longline fisheries such as that for Patagonian toothfish Dissostichus eleginoides in Antarctica. Assuming longline fishing operations affect juveniles more than adults, there is a time lag of 5–10 years before further decreases in population numbers are reflected in the breeding population. Also, because wandering albatrosses are long-lived, population growth rates take approximately 30–50 years to stabilize after a perturbation. Consequently, caution must be exercised when interpreting population trends; short-term (<20 year) estimates may not provide good indications of long-term trends.  相似文献   

11.
Elevated evapotranspiration due to warmer air temperature could raise salinity and nutrient levels of some inland wetlands, potentially impacting nitrogen cycling. To characterize the impact of high evapotranspiration on soil microbial nitrogen cycling in inland wetlands, we compared freshwater and brackish marsh(or non-marsh) wetlands in terms of sediment ammonia-oxidizing rate(AOR), denitrifying rate(DR), and related microbial communities in a typical inland basin, the Hulun Lake basin, in Chi...  相似文献   

12.
Go Grains Health & Nutrition encourages consumption of grain‐based foods in Australia through activities that promote awareness and understanding of the role of grain foods in a healthy diet. Strategies drive the message of the Australian dietary guidelines that a healthy diet should include at least four servings of grain‐based foods every day (1 serving is equal to two slices of bread). The “Go Grains 4+ Serves a Day” program promotes grain‐based foods (refined and whole grain) through the media, website information, resource development, school education, and food industry involvement. Interest in whole grains is growing, reflected in a shift in bread sales over recent years from white to whole grain. Manufacturers are responding with new and reformulated whole grain product launches and an increasing number of products carry packaging statements about whole grain content. Australian food regulations do not permit health claims in packaging or in advertising. In the absence of official guidelines, Go Grains has developed a whole grain daily target intake for use by food manufacturers in packaging. There are limited data publicly available to describe consumption of grain‐based foods in Australia. The findings of a 2009 survey commissioned by Go Grains help provide insight into consumption trends.  相似文献   

13.
Eucalyptus globulus is the most commonly planted hardwood species in industrial plantations in Australia. It is typically planted well out of its natural range and may therefore present a significant risk of exotic pollen-mediated gene flow into native eucalypt populations. This risk was assessed by documenting levels of flowering within plantations, frequencies at which reproductively compatible native species are found adjacent to plantations, levels of F1 hybridisation with native populations, and the existence of F1 hybrid seedling recruitment. We surveyed over 300 plantations across southern Australia over two years. Flower abundance was found to be low with an average of 3% of trees found to flower on an inside row and 7% on the outside edge row of mature plantations. Considerable variation in flowering was found between locations (0–20% of trees reproductive) and 52% of plantations did not have compatible native species growing adjacent. Consequently, 65% of reproductive age plantations presented minimal or low risk of hybridisation due to lack of flowering and/or lack of adjacent compatible native species. Only three out of 10 surveyed high risk plantations were found to hybridise with native eucalypts (Eucalyptus camaldulensis, 0–3% hybrids in open-pollinated seed; Eucalyptus ovata, 0–2%). Established exotic E. ovata × globulus F1 hybrid seedlings were also identified at just one site, in response to disturbance from fire. The potential for gene flow from E. globulus plantations into native eucalypt populations does exist, however, the implementation of an outlined risk management framework would greatly reduce the likelihood.  相似文献   

14.
Field experiments were conducted on a river deposit during 1983–1984 and 1984–1985 in order to study the effect of different soil management practices, such as zero tillage with surface-applied crop residue mulch at a rate of 10 t ha−1 (ZT+M), conventional tillage (CT), CT+ surface-applied crop residue mulch at a rate of 10 t ha−1 (CT + M), CT+crop residue incorporation at a rate of 10 t ha−1 (CT + SI), CT + farmyard manure incorporation at a rate of 10 t ha−1 (CT + FYM), on soil hydro-thermal regime root growth, nutrient uptake and dry matter yield of winter wheat (Triticum aestivum L.). The soils of the site are classified as Entisol, Typic Psammaquent with pH 6.0, cation exchange capacity 10 c mol (p+) per kg in the surface (0–0.3 m) depth. In the CT + M and CT + FYM treatments, higher water retention was observed compared to CI. The minimum soil temperature was also raised by 3°C under CT + M to CT at 0.1-m depth. CT + M and CT + FYM had significantly higher root mass density compared with other treatments at all stages of crop growth. The nitrogen (N) uptake under these two treatments was also significantly higher compared to CT. Under CT+M, plants did not suffer from N stress compared to other treatments. Phosphorus (P) uptake (except at tillering) and potassium (K) uptake under CT+M and CT + FYM were significantly higher than for all the other treatments. Treatments ZT+M and CT+SI behave simply to CT in terms of hydro-thermal regime, root growth, nutrient uptake and dry matter yield. The grain yield under CT+M and CT+FYM during 1983–1984 and 1984–1985 was significantly higher than that under all the other treatments.  相似文献   

15.
This paper summarizes the results of four statistical approaches for the estimation of long-term trends (1983–92) in sulfate concentration data from 90 monitoring sites across the United States. Least squares regression models and nonparametric techniques were applied to these data. Sulfate concentrations were found to be generally decreasing on the order of 0–4% at most sites. There was general agreement that trends were significant in the Great Lakes, Pacific northwest, and southwest regions. Although strengths and weaknesses are described for each approach, all of these approaches are useful for long-term trend estimation. Visualization techniques are recommended for displaying trend patterns and associated levels of statistical significance.  相似文献   

16.
Under semiarid Mediterranean climatic conditions, soils typically have low organic matter content and weak structure resulting in low infiltration rates. Aggregate stability is a quality indicator directly related to soil organic matter, which can be redistributed within soil by tillage. Long-term effects (1983–1996) of tillage systems on water stability of pre-wetted and air dried aggregates, soil organic carbon (SOC) stratification and crop production were studied in a Vertic Luvisol with a loam texture. Tillage treatments included conventional tillage (CT), minimum tillage (MT) and zero tillage (ZT) under winter wheat (Triticum aestivum L.) and vetch (Vicia sativa L.) rotation (W–V), and under continuous monoculture of winter wheat or winter barley (Hordeum vulgare L.) (CM). Aggregate stability of soil at a depth of 0–5 cm was much greater when 1–2 mm aggregates were vacuum wetted prior to sieving (83%) than when slaked (6%). However, slaking resulted in tillage effects that were consistent with changes in SOC. Aggregate stability of slaked aggregates was greater under ZT than under CT or MT in both crop rotations (i.e., 11% vs. 3%, respectively).

SOC under ZT tended to accumulate in the surface soil layer (0–5 and 5–10 cm) at the expense of deeper ones. At depths of 10–20 and 20–30 cm no differences in SOC were encountered among tillage systems, but CT exhibited the highest concentration at 30–40 cm depth. Nevertheless, when comparisons were made on mass basis (Mg ha−1), significant differences in stocked SOC were observed at depths of 0–10 and 0–20 cm, where ZT had the highest SOC content in both rotations. The stock of SOC to a depth of 40 cm, averaged across crop rotations, was greater under ZT (43 Mg ha−1) than under CT (41 Mg ha−1) and MT (40 Mg ha−1) although these figures were not significantly different. Likewise, no significant differences were encountered in the stock of SOC to a depth of 40 cm among crop rotations (i.e., 42 Mg ha−1 for W–V vs. 40 Mg ha−1 for CM).

Crop production with wheat–vetch and continuous cereal showed no differences among tillage systems. Yields were strongly limited by the environmental conditions, particularly the amount of rainfall received in the crop growth season and its distribution. Similar yield and improved soil properties under ZT suggests that it is a more sustainable system for the semiarid Mediterranean region of Spain.  相似文献   


17.
A behaviour-based model was used to explore the effect of an extension of the port at Le Havre (Port 2000), and the effect of proposed mitigation measures, on the mortality and body condition of the three main shorebird species that overwinter in the estuary of the river Seine, France. In the model, a 20% reduction in the area of mudflats on the north side of the estuary had little effect on curlew Numenius arquata mortality and body condition but significantly increased mortality and decreased body condition in dunlin Calidris alpina and oystercatchers Haematopus ostralegus. Disturbance of feeding birds both day and night had a significant effect on the mortality and body condition of all three shorebird species, as did disturbance of roosting birds. Disturbance of feeding birds in the daytime only had a significant effect on dunlin mortality and body condition, but not that of curlew and oystercatchers. In the model, the creation of a buffer zone to reduce disturbance of feeding birds restored shorebird mortality and body condition to pre-disturbance levels. A new mudflat area was also effective in mitigating the effect of habitat loss on all three shorebirds and in mitigating the effect of roost disturbance on dunlin and curlew. However, a new mudflat area was not effective in mitigating the effect of roost disturbance on oystercatcher mortality and body condition. The effectiveness of the mitigating mudflat depended as much on its size as its quality. We believe that this is the first time that anyone has been able to forecast the efficacy of proposed mitigation measures.  相似文献   

18.
Summary We studied the earthworm distribution in a permanent polder grassland by making two detailed surveys in 1983 and in 1990. Geostatistical procedures were used to investigate the changes in species composition and to determine the dispersal rate. Attention was focused on two soil survey variables closely related to earth-worm distribution, the thickness of the Ah horizon and the number of burrows. The dispersal rate between the two survey dates was 13 m year–1 compared with 10 m year–1 before 1983. The difference was attributed either to the development of new population centres due to dispersal by cow's feet or tractor wheels, this altering the spatial dynamics, or to a lag phase in population development in the years following inoculation.  相似文献   

19.
Floristic survey data from spring wetlands in the Great Artesian Basin of Australia were assessed to generate a ranked list of significant flora values. A system was designed to score endemic species and remote populations of plants, using an extensive herbarium database to set the spring flora in context. The sum of these indices for individual wetland complexes yielded a ranked score. The high priority wetland complexes (scoring five or greater) adequately represent their floristic composition, capture all endemic plant species and 76% of the flora. Although data are limited, many of the high value spring wetlands have endemic fauna of which the snails have been most thoroughly surveyed. The procedure provides direction for an efficient conservation program that if implemented should provide security against a range of threatening processes.  相似文献   

20.
黄土丘陵沟壑区小流域基流特点及其影响因子分析   总被引：5，自引：1，他引：4       下载免费PDF全文
在对青海湖高寒湿地进行群落调查的基础上,研究了在群落梯度上高寒湿地的生物多样性与生产力的关系,并探讨了在同一区域内环境的整体性对高寒湿地的生物多样性与生产力关系的影响。运用SPSS软件进行曲线拟合,研究了青海湖内陆高寒湿地物种多样性和地上生物量的关系。研究结果表明,(1)无论是在群落尺度上还是在区域尺度上物种多样性指数与地上生物量呈显著的负相关。(2)在研究区内区域因素对物种多样性和生产力的影响较弱,但如果保持区域环境的整体性则可以有效地提高物种多样性和生产力的相关程度。  相似文献   

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