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1.
Characteristics of bird and small mammal communities can be valuable in monitoring for impacts on specific plots of land. In Utah (USA), significant differences were found among years, habitats and seasons in bird and small mammal abundance, species diversity, and species richness; thus, estimates of these characteristics are consistent and repeatable and can be used for detecting change. Also, bird and small mammal communities are dependent on a wide variety of food resources and habitat characteristics; thus they should reflect a variety of impacts.A comparison is made between two methods of handling bird data from transects: enumeration (individual birds per km) and density (birds per unit area). Correlation between the two was high (r = 0·93). However, density estimates may be necessary to trace an impact to a particular group, guild or species and possibly to its cause.An analysis is made of how much sampling is necessary to make an adequate estimate of the characteristics of bird and small mammal communities. Estimates of bird abundance, species richness and species diversity (from enumeration) may be obtained with three repetitions of 2 km of transect. Three repetitions are also sufficient to estimate abundance of small mammals on 12 by 12 trapping grids. To estimate species richness and species diversity, however, four or more repetitions are needed. Small mammal community characteristics are not well predicted by trapping on transects or small grids except in grids 9 by 9 or larger. These results of sampling effort may only apply to certain habitats but data from bird and small mammal communities should be useful in environmental monitoring at any site.  相似文献   

2.
Studies on temporal changes of tropical bird communities in response to habitat modification are rare. We quantified changes in bird assemblages at the rainforest margin of Lore Lindu National Park, Central Sulawesi, over an interval of 6 years. Standardized bird counts were conducted in the years 2001/2002 and 2008 at 15 census points representing natural forest, secondary forest, agroforest and openland sites. Although overall species richness remained nearly identical, different species groups were affected unequally by habitat modification within the forest margin landscape. The mostly endemic forest species declined in abundance (72.0% of forest species) and were detected at fewer census points in 2008 (56.0%). In contrast, 81.8% of the solely widespread openland birds became more abundant and 63.6% of the species were recorded at a larger number of census points. Hence, recent human activities in the forest margin ecotone negatively affected species of high conservation value. Species richness turned out to be a poor indicator of habitat change, and our results underline the importance of considering species identities. Biotic homogenization as result of habitat conversion is a global phenomenon. In our study, the winners were widespread openland species, while the losers were endemic forest birds. In conclusion, our study shows that 6 years of land-use change had negative impacts on bird community structure and endangered species, but not on overall bird species richness.  相似文献   

3.
In this paper data on the bird community overwintering in the subalpine zone of Sagarmatha National Park (Khumbu Himal area, Nepal) are presented, with particular emphasis on habitat structure and bird-habitat relationships. The impact of land use and management on the conservation of diversity is analysed and discussed. Four habitat types were considered: mixed forest, pure juniper forest, dwarf rhododendron shrubbery and cultivations. Mixed forest supports the richest avifauna, but forest birds are sensitive to over-exploitation of their habitat: bird density, species richness and diversity are significantly lower in heavily utilised forest. Here, the lower density of rhododendrons, firs and birches, together with their younger age, seem to be unattractive to insectivorous gleaners and granivores, which prefer tree- and understorey-rich spots of unutilised forest. Terraced cultivations also are a rich habitat for wintering birds, and traditional cultivations with hedgerows and scattered bushes have a great potential for bird conservation. Juniper woods are important habitats mainly for frugivores, whereas dwarf rhododendron shrubberies support the poorest avifauna. This study emphasises that forest birds and habitats are severely threatened. As deforestation is the consequence of the tourist pressure for fuelwood along the trekking route to Mt. Everest Base Camp, a strict regulation of tourist-related developments is essential to preserve biodiversity and manage land uses within sustainability.  相似文献   

4.
Bird species’ community responses to land use in the suburbanizing Twin Cities, Minnesota, USA, were contrasted among reserves, rural lands, and suburbs. For each land use type, bird composition, diversity, and abundance were recorded for 2 years in ≈99 plots in three sampling units (each ≈4500 ha). A habitat gradient defined by canopy structure (grasslands to savannas to forests) was influenced by land use, so ≈300 plots were used to characterize simultaneous variation in bird communities along land use and habitat gradients. At broad scales (aggregate of 33 plots covering ≈4500 ha) suburbs supported the lowest bird richness and diversity and rural landscapes the most, with reserves slightly below rural. Although reserves were like rural lands in diversity of bird communities, they supported more species of conservation concern, particularly of grasslands and savannas. Differences among land use types varied with habitat structure. Suburbs, rural lands, and reserves had similar forest bird communities, but differed in grassland and savanna bird communities. The extensive rural forests are important for the region’s forest birds. Suburban grasslands and savannas had low shrub abundance, low native bird richness and high non-native bird richness and abundance. However, total bird richness and diversity were as high in suburban as in rural and reserve plots because high native richness in suburban forests and high non-native species richness in suburban grasslands and savannas compensated for lower native richness in suburban grasslands and savannas. Bird conservation here and in the Midwest USA should protect rural forests, expand grasslands and savannas in reserves, and improve habitat quality overall.  相似文献   

5.
Use of native and exotic garden plants by suburban nectarivorous birds   总被引：2，自引：0，他引：2  
A lack of food resources is often used as a reason for the decline in native birds in cities. This study investigated the use of exotic and native nectar resources by the nectarivore guild of birds, which often forms a major component of suburban bird communities in Australia. We investigated the food resource (nectar volume, concentration and sugar reward) of two common native and two exotic garden plant genera. We also determined the relative preference of the nectarivorous bird community for native and exotic plants and examined the relationship between nectarivore foraging preferences and particular garden characteristics. Banksias and grevilleas (native genera) produced significantly higher volumes of nectar than camellias and hibiscus (exotic genera) per floral unit, per plant and per cubic metre of foliage. Banksias also produced significantly more concentrated nectar and consequently a higher sugar reward per floral unit than the other three genera. Fourteen bird species were recorded using the study plants, although only three species were commonly observed feeding: the Red Wattlebird (Anthochaera carunculata), Little Wattlebird (Anthochaera chrysoptera) and Noisy Miner (Manorina melanocephala). Banksia and grevillea plants were preferred by all bird species, which spent significantly more time in banksia than in any other genus. Other variables influencing the time birds spent in a plant were the number of floral units per plant and the number of banksia and callistemon plants present in the garden. Overall, the native genera, banksia and grevillea were not only a more valuable source of food than the exotic genera, camellia and hibiscus, but they were also the preferred foraging sites for suburban nectarivorous birds. Whether the surplus of nectar from native shrubs is associated with territories of larger and aggressive honeyeaters competitively excluding small birds from gardens, is an important research agenda for understanding these urban bird communities.  相似文献   

6.
The objective of this study was to develop an index of biological integrity (IBI) for national-level monitoring of watersheds as an ecosystem health assessment methodology for the South Korean government. A 10-metric IBI model (IBIKW) was developed for watershed management and then applied to 76 streams in four major watersheds in Korea. The model assessments showed that 32.9% of all streams were judged to be in ??excellent?Cgood?? condition, whereas 67.1% were in ??fair?Cpoor?? condition, indicating severely impaired ecological health. Nutrient analyses of stream water revealed a two- to fivefold increase in nutrient and biological oxygen demand (BOD) levels in urban- and cropland-dominant streams compared to forest-dominant streams. The guild structure within the watersheds indicated that tolerant species were predominant in severely degraded regions (BOD?>?6 mg L?1), and sensitive species were distributed in regions with BOD?<?2 mg L?1. Factors affecting ecosystem health (IBIKW scores) included chemical water quality parameters, physical habitat parameters and land use around the stream. In particular, land use was one of the major factors influencing ecosystem health, as indicated by the strong relationships between the percentages of urban and forest streams and the IBIKW scores. The integrated ecosystem health assessment technique developed here can be applied for both regular bioassessments and post-restoration assessments.  相似文献   

7.
We combine mist-net data from 24 disturbance treatments taken from seven studies on the responses of understorey Amazonian birds to selective logging, single and recurrent wildfires, and habitat fragmentation. The different disturbance treatments had distinct effects on avian guild structure, and fire disturbance and the isolation of forest patches resulted in bird communities that were most divergent from those in continuous, undisturbed forest in terms of their species composition. Although low-intensity logging treatments had the least noticeable effects, the composition of understorey birds was still markedly different from the composition in undisturbed forest. This analysis demonstrates the importance of preventing habitat fragmentation and the spread of fires in humid tropical forests, and highlights the need for more research to determine the long-term suitability of large areas of degraded forest for forest birds.  相似文献   

8.
This paper compares lake chemistry in the Adirondack region of New York measured by the Temporally Integrated Monitoring of Ecosystems (TIME) and Adirondack Long-Term Monitoring (ALTM) programs by examining the data from six lakes common to both programs. Both programs were initiated in the early 1990s to track the efficacy of emission reduction policies and to assess the full impacts of acid deposition on surface water chemistry. They now serve to inform on the emerging chemical recovery of these waters. The Adirondack TIME program utilizes a probability-based approach to assess chronic acidification in a population of lakes using one summer sample per year. The ALTM attempts to track changes in both chronic and episodic acidification across a gradient of lake types using monthly samples. The ALTM project has two important attributes that contrast with the TIME program in the Adirondacks: higher temporal resolution (monthly versus once during the summer or fall) and speciation of aluminum. In particular, the ALTM program provides inorganic monomeric aluminum (AlIM), the fraction of Al that is most toxic. The monthly sampling of the ALTM program includes the spring snowmelt period when acid-neutralizing capacity and pH are near their lowest and Al levels are near their highest. We compare chemistry trends (1992?C2008) for sulfate, nitrate, base cations, dissolved organic carbon, hydrogen ion, acid neutralizing capacity, and Al for the six lakes common to both programs. We also compare relatively high springtime AlIM concentrations from the ALTM with relatively low summertime total Al concentrations from the TIME, showing that the ALTM program provides a more biologically relevant indicator of the effects of acid deposition, illustrating the value of the complementary monitoring efforts in the Adirondack region.  相似文献   

9.
We evaluated the contributions of spatial distribution, juxtaposition, and quality of salt marsh habitat to salt marsh breeding birds along the New England coast, USA. We divided the region into two landscapes, Long Island Sound and the Gulf of Maine, based on latitude, geologic and human land use histories, and physical characteristics (tidal amplitude, wave energy). Species richness in both landscapes was at least 20% greater on larger salt marshes. Response to marsh isolation and human development varied regionally, with bird species more sensitive to marsh isolation and road proximity in the more pristine (Gulf of Maine) than altered (Long Island Sound) region. Relatively little overlap was evident between regions in predictors of occurrence and effects of marsh area on particular species. These results indicate that: (1) salt marsh bird communities show similar associations with habitat area and isolation as do forest, grassland, and freshwater wetland bird communities, and (2) landscape context mediates the influence of these parameters on the avian community and should be considered when defining the habitat requirements of salt marsh breeding birds.  相似文献   

10.
Unprecedented deforestation is currently underway in Southeast Asia. Since this trend is likely to continue, it is critical to determine the value of human-modified habitats (e.g., mixed-rural habitat) for conserving the regional native forest avifauna. The impacts of ongoing deforestation on the highly endemic avifauna (33%) of Sulawesi (Indonesia) are poorly understood. We sampled birds in primary and secondary forests in the Lore Lindu National Park in central Sulawesi, as well as the surrounding plantation and mixed-rural habitats. Species richness, species density and population density of forest birds showed a consistent decreasing trend in the following order: primary forests > secondary forests > mixed-rural habitat > plantations. Although primary forests contained the highest proportion (85%) of a total of 34 forest species recorded from our point count surveys, 40-yr old secondary forests and the mixed-rural habitat showed high conservation potential, containing 82% and 76% of the forest species, respectively. Plantations recorded only 32% of the forest bird species. Fifteen forest species had the highest abundance in primary forests, while two species had higher abundance outside primary forests. Our simulations revealed that all forest birds that were sensitive to native tree cover could be found in areas with at least 20% continuous native tree cover. Our study shows that although primary forests have the highest conservation value for forest avifauna, the potential of degraded habitats, such as secondary forests and the mixed-rural habitat, for conserving forest species can be enhanced with appropriate land use and management decisions.  相似文献   

11.
The Adirondack Region of New York State has been identified as having surface waters sensitive to acidic deposition and as receiving large annual inputs of acidic deposition. The large amount of data available for this region makes a quantitative study of the region possible. Compiled from a variety of sources, the Adirondack Watershed Data Base (AWDB) contains information on lake chemistry; lake elevation, area, and volume; and associated watershed data, such as size, slope, aspect, elevation, vegetation and wetland types, beaver activity, fire and logging history, and soils data. Bivariate and multivariate procedures were used to examine relationships between watershed attributes and lake chemistry. Because the variables in the data base are being refined and modified, the current relationships should be considered preliminary. Preliminary results indicate that wet deposition, lake elevation, and forest cover are the principal variables that are associated with variance in the data for lake pH and acid neutralizing capacity (ANC) in the Adirondacks. For headwater lakes in the Adirondacks, we estimate approximately 50% have a total ANC ≤ 40 μeq L?1 and 40% have a pH ≤ 5.5.  相似文献   

12.
I examined the lingering effects of past timber management practices on the vegetation structure and bird community of Kibale National Park, Uganda. I compared four forest treatments: unlogged native forest (UL), two that were selectively logged at low (LL) and high (HL) intensities in the 1960s, and a conifer plantation (PL). Forest-dependent birds were best represented at UL. LL was similar to UL in both vegetation structure and bird community composition, although some forest-dependent bird species were missing from the former. HL had significantly less canopy closure and lower tree density than other plots as a result of the combination of extensive secondary damage and natural disturbance patterns that prevented the reclosure of the forest canopy. Thirty-one percent of the forest-dependent bird species observed during the study were not detected at HL. At PL, bird species richness and bird abundance were about a third of those observed in other plots. There were significant correlations between heterogeneity of tree distribution (horizontal heterogeneity) and abundance and species richness of birds across plots. Abundance and species richness of all, forest-dependent, and forest generalist birds were highest in plots with intermediate measures of horizontal heterogeneity, which were mostly unlogged or lightly logged. If reduced-impact logging practices are not implemented during selective logging operations in tropical forests, consequent long-term changes in vegetation structure may result in significant declines in the populations of some forest-dependent species, as was observed in Kibale National Park.  相似文献   

13.
Habitat loss and fragmentation reduce diversity of tropical bird communities, but the predictability of how communities in fragments disintegrate over time remains unclear. We compared bird community changes of two lowland forest reserves, La Selva Biological Station (LSBS), Costa Rica and Barro Colorado Island (BCI), Panama, both approximately the same size (1500 ha) and at similar latitude (9-10 N) in Central America. Both reserves are losing bird species despite LSBS’s connection to an existing large park (incomplete isolation) and BCI’s favorable location within a largely forested landscape. We examined characteristics of guilds and species lost from the sites to determine whether patterns were similar, and thus predictable. Some of the same guilds declined at both reserves, particularly insectivores and ground/understory nesters. At LSBS mixed-species flock participants, forest species, and burrow-nesters also declined or became extirpated disproportionately. At BCI edge species became extirpated. Body mass was a poor predictor of species and guild loss at both sites, except for carnivores at La Selva. Thus, fragmentation appears to influence some guilds more than others, but which species decline or disappear in tropical forest fragments is also influenced by site-specific factors, mostly yet to be determined. We need to understand such idiosyncratic effects of fragmentation better, rather than rely on one-size-fits-all management plans to conserve bird communities in tropical forest fragments.  相似文献   

14.
There is a paucity of research on the wider landscape-level effects of ski-piste construction on alpine fauna. In this study, the response of alpine bird communities to the landscape changes induced by the construction of ski-pistes was investigated in the western Italian Alps. The aims were: (i) to test the hypothesis that ski-pistes have a detrimental effect on alpine grassland bird communities at a landscape-scale; and, (ii) to model local probability distributions of bird species according to different scenarios of ski-piste restoration and ski-piste proliferation above the treeline. Species richness and presence/absence data from point counts were analyzed in relation to GIS-derived landscape variables based on a 16 ha hexagon grid. Predictive variables were selected through the LASSO model selection procedure, and logistic regression was used to estimate the probability of occurrence of each species in each hexagon. Grassland species richness, and probability of occurrence of water pipit, wheatear and black redstart, significantly decreased with increasing extent of ski-piste edge. Length of ski-piste edge was in the set of best models considering a large range of habitat and landscape predictors, and are therefore clearly features that exert a strong negative effect on high alpine grassland bird communities. Predictions of species occurrence were made by applying the models to different scenarios of habitat change. These showed predicted detrimental impacts of a relatively small 10% increase in ski-piste extent, but also that grassland restoration on existing ski-pistes could result in significantly increased occurrence rates of alpine grassland species. This study suggests that ski-pistes are perceived by birds as detrimental features of the alpine landscape. To minimize their impact, new, environmentally–friendly ways of constructing pistes should be developed, which could include habitat restoration and management to obtain a level of grass cover such that edges of ski-pistes are no longer perceived by birds.  相似文献   

15.
The federally endangered Karner blue butterfly (Lycaeides samuelis) is the focal species for a conservation plan designed to create and maintain barrens habitats. We investigated whether habitat management for Karner blue butterflies influences avian community structure at Fort McCoy Military Installation in Wisconsin, USA. From 2007 through 2009 breeding bird point count and habitat characteristic data were collected at 186 sample points in five habitat types including two remnant barrens types, barrens habitat restored from woodland and managed specifically for the Karner blue butterfly, and two woodland habitat types. Although the bird community of managed barrens was not identical to the communities of remnant barrens, the Field Sparrow (Spizella pusilla), a species of conservation concern, and sparse canopy associated bird species, such as the Baltimore Oriole (Icterus galbula) and Eastern Bluebird (Sialia sialis) were predicted to occupy managed barrens and remnant barrens in similar proportions. Adjacent habitat was the most influential factor in determining the community of bird species using the managed barrens. In Wisconsin, and likely throughout the range of the Karner blue butterfly, management for the butterfly creates habitat that attracts a bird community similar to that of remnant barrens, and benefits several avian species of conservation concern. Additionally, the landscape context surrounding the managed habitat influences avian community composition. Managed barrens that are adjacent to remnant barrens, rather than adjacent to woodland habitats, have the highest potential for conserving barrens breeding birds.  相似文献   

16.
We show how Chilean forest bird species richness, abundance and guild structure changes as a function of structural properties of forest stands. We surveyed bird assemblages in two old-growth (>200 years), two mid-successional (30-60 years), and two early-successional forest stands (4-20 years), from November 1999 to September 2000, on Chiloé Island, southern Chile (42°S). Birds were grouped into four habitat-use guilds: large-tree users, vertical-profile generalists, understory species, and shrub-users that occasionally use forests. We recorded a total of 24 bird species: 21 in old-growth, 14 in mid-successional and 16 in early-successional stands. Large-tree users and understory birds were most abundant in old-growth stands, vertical-profile generalists were common in both old-growth and mid-successional stands, and shrub-users were only common in early-successional stands. For nine bird species we found significant relationships between their local abundance and forest structural elements. Higher bird densities in old-growth forests were associated with greater availability of canopy emergent trees, snags, logs and understory bamboo cover in this habitat. Accordingly, bird species diversity in forest stands can be predicted by the presence of these structural elements, and forests should be managed to conserve structural elements that create favorable habitat for bird species in order to prevent future species losses due to logging practices.  相似文献   

17.
Woodpeckers (family Picidae) show promise as indicators of avian diversity in forests because their populations can be reliably monitored, and their foraging and nesting activities can positively influence the abundance and richness of other forest birds. A correlation between woodpecker richness and richness of forest birds is known to exist at the landscape scale, but uncertainty remains whether this correlation occurs at the smaller stand-level spatial scales where forest management activities take place. We used data collected under a diverse range of forest types, harvest treatments, and forest health conditions during a long-term study of bird communities in interior British Columbia, Canada, to examine two basic questions: (1) at the level of individual forest stands, is woodpecker richness correlated with bird richness (measured as richness of all other bird species)? and (2) do woodpecker richness and bird richness have similar habitat correlates? Bird richness was positively correlated with woodpecker richness (β = 0.59, SE = 0.22, 95% CI = [0.14 1.03]). Richness of both woodpeckers and all other birds were positively correlated with tree species richness and negatively correlated with density of pines, and the effect for forest harvest type was similar for both measures of avian richness (uncut < partial harvest < clearcut with reserves). The effect of density of lodgepole pines killed by mountain pine beetles differed between the two richness measures, being positive for woodpecker richness and negative for forest bird richness. We conclude that the richness of woodpeckers is indeed correlated with the richness of other birds at the stand-level, and can serve as a reliable indicator of overall bird richness in most forest stands and conditions, except during insect outbreaks when differential responses by woodpeckers and the rest of the avian community may decouple the relationship between bird richness and woodpecker richness.  相似文献   

18.
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   

19.
We investigated the diversity of breeding bird communities in 53 oases in southern Tunisia. In particular, we examined the similarity of bird communities among oases in relation to vegetation structure and geographic location. We found that oases close to each other supported similar bird communities, suggesting that the spatial distribution of oases has played an important role in shaping local communities. Accounting for oasis location, bird richness was related to oasis size and to vegetation traits, namely to the diversity of trees and herbaceous plants. Oases within which traditional practices are used to diversify the agricultural products were found to provide more suitable habitat conditions for birds than modern plantations created to maximize the production of dates. Traditional oases represent semi-natural habitats within which traditional human activities may be essential for maintaining their biodiversity, and we think that more attention to the conservation of these systems is to be paid.  相似文献   

20.
This paper addresses the factors that constrain the assembly of earthworm communities in temperate land use systems. An occurrence matrix containing 44 localities and 20 species was build from data sets of different studies carried out in Haute Normandie (France). The whole data set included species lists from the three main landscape units and from a range of land use types from unmanaged forests and grasslands to intensive pastures and annual crops. We used species pool, multivariate (correspondence analysis) and null model analyse to explore how species occurring in a given community are sorted from the regional species pool. Special attention was paid to identifying non-randomness in co-occurrence and morpho-ecological patterns and to describing community patterns in response to habitat constraints. Twenty species of Lumbricidae were identified in the total species pool. We found no significant effect of landscape units on species richness and density, while land use type had a significant impact on both variables, with the lowest values in crops and forests, and the highest values in grasslands. Correspondence analysis highlighted how broad land use types, soil gradients and land use intensity influence patterns of community composition and ecological coherence. Non-random patterns in guild proportion were found in a few situations, with differences between grasslands and forests. This shows that environmental filters select species at specific scales according to particular ecological traits, resulting in a convergence of these traits between species of a given community. Local species richness never exceeded nine species and species co-occurrence was significantly lower than expected by chance and much lower than described in the literature for other taxa. Although no significant patterns of limiting similarity were observed at the scale of our study, we conclude that earthworm communities are also highly structured by competition. Our study thus agrees with the idea that both habitat and competitive constraints operate simultaneously to determine how community assembly takes place.  相似文献   

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