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1.
The negative consequences of lead shot ingestion have been demonstrated in captive birds, and the prevalence of embedded shot has been measured in wild waterfowl several times. However, the long-term consequences of these two indirect outcomes of hunting on waterfowl survival have merely been investigated. Using data from about 40,000 X-rayed teals (Anas crecca), this study attempts to evaluate these effects. We used multivariate logistic regressions to model the probability of carrying shot in the flesh or in the gizzard while testing for various explanatory variables such as sex, age, time or morphological measures like mass and flattened wing length. Because of technical issues, we used a non-parametric sign test rather than a complete capture-recapture analysis to evaluate the effect of shot on teal survival. This test was applied to the differences in time between ringing and recovery for lead categories (no lead shot, ?1 shot in the flesh but none in the gizzard, ?1 shot in the gizzard but none in the flesh) compared two by two. We show that, overall, males are more likely to carry embedded shot than females whereas the latter are more likely to carry lead pellets in the gizzard. Similarly, adults are more likely to carry shot in the flesh whereas first year individuals are more likely to have pellets in the gizzard. Embedded shot tend to accumulate in the ducks body over time, i.e. with the number of encounters with hunters, with no significant effect on survival. Conversely, the probability of carrying shot in the gizzard decreases over time, because lead-poisoning quickly leads the individual to death. Several possible biological interpretations are put forward to explain those results. This study demonstrates that negative impacts of ingested lead on teal survival arise after only one single pellet is ingested, advocating the ban of lead ammunition.  相似文献   

2.
The Transvaal Threatened Plants Programme was initiated during 1976. After the publication of the first Threatened Plants Report for Southern Africa during 1980 (Hall et al., 1980) considerable progress has been made with the programme. The progress made with the taxonomic, practical, analytical phases and conservation of threatened plants is discussed. Although certain objectives were not achieved during the survey, sufficient data have been accumulated to recommend 43 conservation category changes. A total of 23 species were eliminated from the list of 216 threatened species of the Transvaal based on the findings of the distribution surveys. An updated checklist of 246 threatened plants, which includes 53 new threatened species, is presented for the Transvaal.  相似文献   

3.
Egyptian vulture populations have decreased sharply in the Western Palearctic; island populations are almost extinct in the Mediterranean and the Macaronesian regions. In the Canary archipelago, the species only survives in the islands of Fuerteventura and Lanzarote. During 1998-2001 we examined population parameters and evaluated some potential limiting factors for this isolated and sedentary population. The total population (breeding and non-breeding birds) was monitored annually. In addition, 26 fledglings and 33 immatures (<6 years old) and adult birds were captured for individual marking with plastic rings. Twenty-three/twenty-four occupied territories were located in the island and the total population estimated at around 130 birds. Breeding success was lower than recorded elsewhere in the species' distribution area: only 0.43 fledglings/pair/year were produced. Adult (>6 years old birds) and immature annual survival rates were similar, around 90%. Adult survival was lower than expected as territorial birds seem more susceptible to poisoning. Immature survival could be favoured by the existence of regular feeding places. Casualties from power lines was the main cause of mortality (12 cases during the study period). Blood sampling revealed high frequencies of lead poisoning: 13.5 and 2.7% of individuals showed sub-clinical and clinical intoxication levels, respectively, probably caused by the ingestion of lead shot. Priority conservation measures should be directed to reduce electrocution risks, illegal poisoning, and lead contamination. Population reinforcement with birds coming from other populations is not recommended as previous information reveals morphological and genetic differentiation of Canarian Egyptian vultures compared with continental populations.  相似文献   

4.
Raptors that consume game species may ingest lead fragments or shot embedded in their prey’s flesh. Threatened Spanish imperial eagles Aquila adalberti feed on greylag geese in southern Spain in winter, and often ingest lead shot. We analysed bone and feather samples from 65 Spanish imperial eagle museum specimens collected between 1980 and 1999, to investigate the prevalence of elevated lead concentrations. Four of 34 birds (12%) had very elevated bone lead concentrations. All four birds were young and the concentrations were outliers to the distribution, suggesting probable exposure to lead gunshot. Excluding these elevated lead outliers, bone lead concentrations were correlated with the bird’s age at death. Three of 41 feathers (7%) had elevated lead concentrations, indicative of high exposure during feather formation. When these outliers were omitted, feather lead concentration was correlated with the age of museum specimens, suggesting that a high proportion of feather lead was exogenous, deposited after specimen collection. Therefore, careful interpretation of feather lead concentrations is required to separate endogenous and exogenous lead. We discuss the potential significance of lead poisoning in Spanish imperial eagles and other raptors, and recommend measures for its reduction.  相似文献   

5.
Lead poisoning is not a new threat for wild birds, but it is now playing an important role in shaping raptor populations. Studies have been focused mainly on Europe, North-America, and Japan, but little is known about the situation in South-America. Lead is a serious threat for wildlife, especially for long-lived species. Nevertheless, no information is available for wild Andean condor (Vultur gryphus) populations. This species, which lives throughout the Andes Mountains, is endangered mainly in the north though it is having problems throughout its distribution. We evaluated lead exposure in the Andean condor by a non-destructive method using feathers. We determined lead concentration from 152 feathers, collected in 15 communal roosts distributed throughout almost all condor’s range in Patagonia (ca. 1500 km north–south). We also looked for the origin of this lead through the analysis of lead isotope composition of feathers and ammunition. We present here the first reference data on lead concentration for a raptor population from Argentina. Lead concentrations were generally low, however, some individuals had concentrations several times above the overall mean (up to 21 μg/g). Our results suggest that lead might come from a mix of two types of ammunition sources, one used for big game and another for hare hunting. Andean condors are at the top of the food chain, thus all the other medium-to-large sized scavengers and predators from this area can be also exposed to this threat. We highlight the need to change hunting policies in Argentina, and in other South-American countries, including the banning of lead ammunitions to protect carnivores consuming hunted animals.  相似文献   

6.
The objective of this study was to assess the extent of lead pellet ingestion by British wildfowl, particularly ducks and geese, and to examine regional variations. The gizzard contents of 2445 shot and 238 found-dead birds were examined, and lead concentrations were determined for 1620 liver and 1841 wing bone samples. In addition, X-ray photographs and blood samples were taken from live-caught birds. Ingested lead pellets were found in 3·2% of the birds examined. For a range of species, including pink-footed goose, white-fronted goose, barnacle goose, wigeon, teal, pintail, shoveler, scaup and moorhen, recorded incidences were either very low or zero. Relatively high incidences were noted for swans, greylag goose (7·1% of shot birds), gadwall (11·8%), mallard (4·2%), pochard (10·9%), tufted duck (11·7%) and goldeneye (6·7%). Most ingested pellets originated from shotguns, though anglers' split shot were found in one pochard and four mute swans. A marked seasonal variation in the extent of pellet ingestion was noted for mallard, with a peak in September, and evidence of high levels immediately before and after the shooting season. Pellet ingestion by mallard was found to be of widespread occurrence, though with considerable variation in recorded incidence from place to place. Inland areas tended to be worse, with the highest incidences recorded for birds shot at flight ponds and other freshwater bodies. Six per cent of mallard shot at inland sites contained ingested pellets, compared with 2·6% of those collected from coastal areas. The observed extent of pellet ingestion in British mallard is calculated directly to cause the death of at least 8000 each winter. Some measures that could be taken to alleviate the lead-poisoning problem in Britain are discussed, and progress of the USA's non-toxic pellet programme is examined.  相似文献   

7.
Theoretical advances in systematic reserve design aim to promote the efficient use of limited conservation resources and to increase the likelihood that reserve networks enhance the persistence of valued species and ecosystems. However, these methods have rarely been applied to species that rely on spatially disjunct habitats. We used the marbled murrelet, a seabird that requires old-growth forest in which to nest and high quality marine habitats in which to forage, as a case study to explore methods of incorporating multiple ecological values into single species spatial reserve design. Specifically, we used the cost function in MARXAN to include the ecological value of marine habitats while identifying spatial solutions for terrestrial nesting habitat reserves. Including marine values influenced terrestrial reserve designs most when terrestrial habitat targets were low and little or none of the target was represented in pre-existing protected areas. Our results suggest that including marine values in the planning process will influence marbled murrelet terrestrial reserve designs most where substantial terrestrial nesting habitat still exists, where new reserves are relatively unconstrained by pre-existing reserves, or when conservation resources only allow the protection of a small fraction of available habitat. This paper presents a novel framework for incorporating multiple measures of ecological value in the spatial reserve design process and should be particularly useful for species that rely on multiple habitats during their life cycle.  相似文献   

8.
Estimates of the number of waterbirds (principally wildfowl) wintering in Great Britain are presented, based on data from the period 1994/1995-1998/1999. These update the previous estimates for 1987/1988-1991/1992. National estimates are used to derive 1% thresholds for waterbird species which in turn form the basis for the identification of nationally important wetland sites for subsequent conservation and protection. Estimates are also used to assess changes in numbers of those species for which monitoring data are insufficient to calculate annual indices of population change. Data for calculating the estimates come from a variety of sources including the Wetland Bird Survey (WeBS, a long-term scheme which counts waterbirds by day at wetlands), goose roost censuses, site-based surveys and published reviews. Generation of the estimates is made difficult by a number of methodological and data quality issues. To account for some of the methodological problems affecting WeBS data, new methods for generating estimates have been used which account for birds missed during the counts in a more comprehensive manner. These result in large increases in the estimated numbers for many of the relevant species, although most are still considered to be underestimates. To assess the biological change in numbers since the last assessment, estimates generated from the same methods used previously are also presented. These indicate that while the majority of species have experienced increases in numbers since the late 1980s there have been some notable declines. There is however scope for improving the accuracy of estimates derived from extensive, volunteer-based monitoring schemes such as WeBS.  相似文献   

9.
The Guadalquivir Marshes or Doñana wetland complex is the most important wintering site for migratory waterbirds in the Mediterranean region. However, there is a lack of previous information on the status of different species in this area. Using monthly aerial counts conducted from 1978 to 2005, we analysed the size of wintering populations of 21 waterbird species, their distribution within the Guadalquivir Marshes, and their long-term population trends. We used Underhill indices to replace missing values and to correct for flocks of unidentified ducks. Based on long-term means, we identified 16 species whose populations at Doñana exceed 1% of the biogeographical flyway population. For at least 1 month of the year, mean counts were around 10% of the flyway population for six species. The natural, temporary marshes of Doñana National Park were particularly important for Anatidae, ricefields for gulls, white storks and grey herons, fish ponds for flamingos, cormorants and avocets, and salt pans for shelduck. Four Anatidae species have undergone long-term declines and eight non-Anatidae have undergone long-term increases. Population trends were related with trophic guild, migratory status and habitat use. Winter visitors and herbivorous species showed more negative trends than resident, omnivorous-carnivorous species. Those species concentrated in strictly-protected natural marshes have tended to decline. The surface area of ricefields and fish ponds has increased over the study period, and bird species concentrated in these artificial wetlands have tended to increase. This raises questions about the value of waterbirds as flagship or umbrella species for wetland conservation.  相似文献   

10.
IUCN Red List conservation status is apparently judged mainly by assessment of species' susceptibility to threat. However, risk must often depend also on the threat itself. Therefore, we investigate the value of adding to IUCN's current criteria a separate index of threat, human density. Human density in the geographic range of Threatened primate species is significantly higher than in the range of Lower Risk species. Thus, Threatened species are both susceptible, and experience more threat. However, the match is far from perfect. Given abundant other evidence of adverse effects of high human density, the mismatch emphasizes the potential benefit of adding an index of threat to the current criteria. A main advantage might be improved assessment, given the amount of up-to-date data on threats compared with the paucity on reactions to threat. The simplest means of incorporation might be to increase the status of species that experience higher than a certain threshold human density.  相似文献   

11.
The attraction of wintering waterbirds to freshwater flowing over intertidal mudflats of estuaries was studied between 1996 and 1998. This was a response to the increasing levels of freshwater abstraction around internationally protected estuaries in the UK, as its relevance to waterbirds was largely undocumented. The numbers and densities of waterbirds in corridors around freshwater flows were consistently greater than those on the remaining mudflats at all estuaries studied. Large proportions of the estuary populations of several species sometimes occurred around flows. The attraction of freshwater on mudflats to waterbirds, especially ducks and geese, is probably attributable to the presence of water for preening and drinking close to their feeding grounds. Microclimate and shelter may be enhanced, and prey density or availability may be increased for foraging birds on wet mudflats. The amount of freshwater in flows was important to several species and greater densities occurred around larger discharges although very large discharges across narrow mudflats created deep, incised creeks that were unsuitable for most waterbirds. Thresholds of discharge attractive to birds are likely to be estuary-specific and depend on the width of mudflat if freshwater is to reach mid and lower shores at low tide. Surrounding landscapes also influenced the variability of discharge and therefore the predictability of flows. The impact on birds from freshwater abstraction may be similar to effects of displacement from other intertidal grounds and could affect large numbers of birds. The potential impact on bird populations should be included in assessments wherever there are proposals to alter or remove discharges within estuaries.  相似文献   

12.
Gough Island is a remote Southern Ocean Island that, despite having no permanent human population, is under substantial conservation threat as a result of human activity. A considerable proportion of the flora and fauna has been accidentally introduced, and new data are presented showing that ca. 70% of the free-living pterygote insect species are introductions. We describe how endangered seabirds that breed on the island may suffer from human fisheries activities and present new evidence showing that local temperatures have risen significantly since 1963, threatening to alter the architecture and composition of species communities. These observations are an indication that the terrestrial ecosystems of other remote islands in the Southern Oceans may be under greater conservation threat than previously thought. In light of the threats described, we discuss conservation management priorities for Gough Island. To facilitate conservation of the indigenous biota, and that of similar islands elsewhere, we suggest that a combination of proactive measures designed to maintain the integrity of island communities, and monitoring programs designed rapidly to identify new conservation threats, should be implemented conscientiously.  相似文献   

13.
The subdesert mesite, a terrestrial non-passerine bird endemic to the Mikea Forest of southwest Madagascar, is currently classified as globally threatened (category: Vulnerable). However, accurate assessment of threat in accordance with the IUCN Red List criteria (A, B and C) requires data on effective population size, area of habitat occupied and rate of decline, none of which is available for this species. Here we present the first empirical estimates of its population size using five complementary methods, three incorporating data on territory size and two using data gathered during call-playback surveys conducted throughout its entire global range. Estimates vary from 98,000 to 152,000 individuals, with the most reliable possibly being that generated by distance sampling (115,000). This figure is more than an order of magnitude greater than the only published estimate of <10,000 individuals. By analysing data on forest cover change, we estimate the population of the subdesert mesite to have declined by, at most, 10% in three generations. Although the rate of deforestation in 1994-1999 is double that calculated for 1962-1994, it is deemed unlikely that the population will decline by 20% over the next three generations. As such the species fails to meet criterion A. Although the subdesert mesite's range and area of occupancy are small, they are not fragmented and do not comprise fewer than 10 locations. Consequently, this species does not meet criterion B. Further, the species fails to meet criterion C, for which a maximum of 10,000 mature adults is required. According to IUCN (2000 Red List of Threatened Species) this species should therefore be downlisted in status. We discuss why it still warrants conservation attention and suggest the need for modifications to the criteria thresholds in relation to basic information about the ecology and taxonomic distinctness of species.  相似文献   

14.
Biological invasions constitute one of the most important threats to biodiversity. This is especially true for “naïve” birds that have evolved in the absence of terrestrial predators in island ecosystems. The American mink (Mustela vison) has recently established a feral population on Navarino Island (55°S), southern Chile, where it represents a new guild of terrestrial mammal predators. We investigated the impact of mink on ground-nesting coastal waterbirds with the aim of deriving a vulnerability profile for birds as a function of different breeding strategies, habitat, and nest characteristics. We compared rates of nest survival and mink predation on 102 nests of solitary nesting species (Chloephaga picta, Tachyeres pteneres), on 361 nests of colonial birds (Larus dominicanus, Larus scoresbii, Sterna hirundinacea), and on 558 artificial nests. We calculated relative mink and bird densities at all nest sites. Nests of colonial species showed the highest nest survival probabilities (67-84%) and no predation by mink. Nest survival rates for solitary nesting species were lower (5-20%) and mink predation rates higher (10-44%). Discriminant analyses revealed that mink preyed upon artificial nests mainly at shores with rocky outcroppings where mink were abundant. High nest concealment increased the probability for predation by mink. Conservation planning should consider that invasive mink might severely affect the reproduction success of bird species with the following characteristics: solitary nesting, nesting habitat at rocky outcrop shores, and concealed nests. We recommend that work starts immediately to control the mink population with a priority in the nesting habitats of vulnerable endemic waterbirds.  相似文献   

15.
Freshwater ecosystems represent one of the most threatened broad habitat types globally. Despite containing around a third of all vertebrates, area-based approaches to conservation planning rarely include freshwater species as an explicit target for conservation. Here we describe and apply a globally applicable methodology comparable to those for other groups (i.e. Important Bird Areas) to identify river and lake catchments that represent, or contain, freshwater Key Biodiversity Areas. We discuss the rationale behind the methodology and propose appropriate definitions and quantitative threshold values for the selection criteria. Thresholds are developed through spatial analysis of species information for four comprehensively assessed freshwater taxonomic groups in continental Africa, comprising 4203 species, as recently assessed for the IUCN Red List of Threatened Species?. To illustrate application of the methodology freshwater Key Biodiversity Areas are identified across continental Africa, and conservation planning software used to prioritise a network of catchments that captures 99% of the total species complement within catchments covering ca. 20% of the total land area. Within these prioritised catchments only 19% of river length falls within existing Protected Areas suggesting that, given the high connectivity within freshwater ecosystems and their dependence upon catchment management for effective conservation, modification or expansion of the protected area network is required to increase effective conservation of freshwater species. By applying this methodology, gaps in the coverage of freshwater species by existing Protected Areas can be identified and used to inform conservation policy and investment to ensure it is inclusive of, and effective for, freshwater biodiversity.  相似文献   

16.
In countries with high human populations, using agricultural areas as multifunctional systems to produce food for humans and retain wildlife may be an efficient conservation strategy for many species. Inclusion of natural habitat and species requirements on agricultural landscapes explicitly into planning processes are precluded by lack of information on drivers of species persistence. Climate change is an additional emerging complexity, and adaptation plans for agricultural landscapes are biased towards intensification to secure long-range food production. I examine the conservation potential of an agricultural landscape in two districts of Uttar Pradesh, north India where agricultural intensification and altered rainfall patterns are predicted to occur. I assess stressors affecting breeding success over eight years of two large waterbirds of conservation concern – Sarus Cranes and Black-necked Storks. Both species had high breeding success that improved with total rainfall and more wetlands in breeding territories. Agricultural and township expansions deteriorated territory quality and reduced breeding success. Sarus Crane populations were predicted to decline relatively rapidly if development activities continued to displace breeding pairs. Black-necked Storks appeared resilient over the long-term notwithstanding reduced breeding success in low-rainfall years. Waterbird nesting habitats (wetlands and trees) were retained in Uttar Pradesh as community lands by villages and by state government via legal provisions suggesting the utility of multiple conservation approaches. Incorporating species requirements explicitly, alongside traditional land use practices conducive for habitat conservation, into adaptation planning and conservation policy will be necessary to retain long-term multifunctionality of such agricultural landscapes.  相似文献   

17.
Several studies have compared the performances of exact algorithms (integer programming) and heuristic methods in the solution of conservation resource allocation problems, with the conclusion that exact methods are always preferable. Here, I summarize a potentially major deficiency in how the relationship between exact and heuristic methods has been presented: the above comparisons have all been done using relatively simple (linear) maximum coverage or minimum set models that are by definition solvable using integer programming. In contrast, heuristic or meta-heuristic algorithms can be applied to less simplified nonlinear and/or stochastic problems. The focus of this study is two kinds of suboptimality, first-stage suboptimality caused by model simplification and second-stage suboptimality caused by inexact solution. Evidence from comparisons between integer programming and heuristic solution methods suggests a suboptimality level of around 3%-10% for well-chosen heuristics, much depending on the problem and data. There is also largely anecdotal evidence from a few studies that have evaluated results from simplified conservation resource allocation problems using more complicated (nonlinear) models. These studies have found that dropping components such as habitat loss rates or connectivity effects from the model can lead to suboptimality from 5% to 50%. Consequently, I suggest that more attention should be given to two topics, first, how the performance of a conservation plan should be evaluated, and second, what are the consequences of simplifying the ideal conservation resource allocation model? Factors that may lead to relatively complicated problem formulations include connectivity and evaluation of long-term persistence, stochastic habitat loss and availability, species interactions, and distributions that shift due to climate change.  相似文献   

18.
The buffer effect predicts that where the reproductive success and survivorship of a species vary between potential habitats, sites will be sequentially filled according to a preference hierarchy. Once favoured sites reach saturation, numbers on the less-suitable/poorer quality sites will show a greater rate of increase compared with those on favoured sites. Supporting evidence for a buffer effect is readily available in the literature for many species, although this is generally restricted to small-scale analyses. In this paper we test for a buffer effect on a national scale for 19 species of waterbirds regularly wintering in the UK for which populations have increased nationally. The results provide little support for the effect, with only four species showing significant negative correlations. Nonetheless, a number of factors are likely to confound the occurrence/identification of a buffer effect for these species, including site area and data limitations. By contrast, for the majority of these 19 species, those sites where initial population totals are largest are also those with the fastest rates of population increase. Encouragingly, these sites are, therefore, more likely to be classified and managed as Special Protection Areas (SPAs) or Ramsar sites using the current numerical criteria for identifying such conservation areas.  相似文献   

19.
The integration of freshwater and terrestrial biodiversity priorities in systematic conservation planning is a major challenge to conservation planners. Maintaining upstream–downstream connectivity and the influence of catchments on freshwater ecological integrity are some of the issues that make it difficult to reconcile terrestrial and freshwater conservation planning. As a result most conservation assessments are often biased towards terrestrial systems without adequate incorporation of freshwater biodiversity in determining priority areas for conservation. In this paper, we propose a protocol for integrating the assessment of freshwater and terrestrial priorities in conservation planning, based on a case study from Mpumalanga Province in South Africa. The approach involves the separate assessment of freshwater priority areas, and using the outcome to influence the selection of terrestrial priority areas. This allowed both freshwater and terrestrial biodiversity to be incorporated in conservation planning without compromising their unique requirements. To test the effectiveness of this approach, we assessed percentage overlap between freshwater and terrestrial priority areas, target achievement, and the area required to achieve targets. We then compared the outcome from the proposed approach with the separate assessments of freshwater and terrestrial biodiversity priorities, and when both systems are given an equal weighting in a single assessment. The results showed that there was a noticeable improvement in the overlap of priority areas for freshwater and terrestrial biodiversity from 23% to 47%. Target achievement for freshwater biodiversity improved by 10% when terrestrial assessment was based on freshwater priority areas as opposed to terrestrial systems being assessed alone. There was negligible increase in area required, whether there was integration of freshwater and terrestrial biodiversity or no integration. We conclude that the most efficient way to achieve integration in conservation planning is to preferentially select areas where freshwater and terrestrial biodiversity priorities overlap.  相似文献   

20.
In New Zealand, the endemic kaki or black stilt (Himantopus novaezelandiae) has been the focus of intensive conservation management for the past 20 years. Threatened by predation and habitat loss, the population fell to as low as 23 birds before management was implemented to reverse the decline. Predator trapping has been one form of management intervention in the wild, yet despite 20 years of control, there is only limited evidence to suggest that predator trapping is beneficial for the survival of kaki. Lack of adequate experimental design and understanding of the predator-prey dynamics in the system in which kaki live appear to be the main reasons why the benefits of predator control are not consistently clear. An adaptive management approach would have provided more information on the efficacy of predator trapping and increased understanding of the inter-relationships between kaki survival and predator abundance.  相似文献   

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