首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Land‐use intensification has consequences for biodiversity and ecosystem functioning, with various taxonomic groups differing widely in their sensitivity. As land‐use intensification alters habitat structure and resource availability, both factors may contribute to explaining differences in animal species diversity. Within the local animal assemblages the flying vertebrates, bats and birds, provide important and partly complementary ecosystem functions. We tested how bats and birds respond to land‐use intensification and compared abundance, species richness, and community composition across a land‐use gradient including forest, traditional agroforests (home garden), coffee plantations and grasslands on Mount Kilimanjaro, Tanzania. Furthermore, we asked how sensitive different habitat and feeding guilds of bats and birds react to land‐use intensification and the associated alterations in vegetation structure and food resource availability. In contrast to our expectations, land‐use intensification had no negative effect on species richness and abundance of all birds and bats. However, some habitat and feeding guilds, in particular forest specialist and frugivorous birds, were highly sensitive to land‐use intensification. Although the habitat guilds of both, birds and bats, depended on a certain degree of vegetation structure, total bat and bird abundance was mediated primarily by the availability of the respective food resources. Even though the highly structured southern slopes of Mount Kilimanjaro are able to maintain diverse bat and bird assemblages, the sensitivity of avian forest specialists against land‐use intensification and the dependence of the bat and bird habitat guilds on a certain vegetation structure demonstrate that conservation plans should place special emphasis on these guilds.  相似文献   

2.
Human driven changes in land‐use have increased the need to understand how landscape structure affects species distribution. We studied how forest edges affected the distribution of birds in grasslands recently encroached by forest patches. We investigated how species’ biological traits influenced their response to vegetation change near forest edges. We censured birds along 300‐m line transects run into the open habitat perpendicularly to forest edges. We recorded habitat variables and landscape context along each transect and characterized edges and forest patches. We recorded 33 bird species in 153 transects for a total of 654 individuals. We analyzed species response to edges with generalized linear mixed models. Habitat preference was prevalent to explain species response to forest edges. The abundance of open‐habitat birds such as skylark Alauda arvensis decreased significantly in the vicinity of edges. This negative response extended within 150 m from the edge. The effect was disproportionately higher in open‐habitat species with high conservation concern. The abundance of species feeding or/and breeding in both forest and open habitat, such as woodlarks Lullula arborea, sharply increased near edges (positive edge response). Abundance of shrub and non‐shrub dependent species increased with distance to edge. The two species groups did no differ in abundance/distance to edge relationship. Intensity of species response to forest edges varied among transects in relation to transect vegetation characteristics. Edge length or aspect, diet and nest height had no direct effect. We discuss the possible role of variation in resources and nest predation risk to explain observed patterns.  相似文献   

3.
Avian species persistence in a forest patch is strongly related to the degree of isolation and size of a forest patch and the vegetation structure within a patch and its matrix are important predictors of bird habitat suitability. A combination of space‐borne optical (Landsat), ALOS‐PALSAR (radar), and airborne Light Detection and Ranging (LiDAR) data was used for assessing variation in forest structure across forest patches that had undergone different levels of forest degradation in a logged forest—agricultural landscape in Southern Laos. The efficacy of different remote sensing (RS) data sources in distinguishing forest patches that had different seizes, configurations, and vegetation structure was examined. These data were found to be sensitive to the varying levels of degradation of the different patch categories. Additionally, the role of local scale forest structure variables (characterized using the different RS data and patch area) and landscape variables (characterized by distance from different forest patches) in influencing habitat preferences of International Union for Conservation of Nature (IUCN) Red listed birds found in the study area was examined. A machine learning algorithm, MaxEnt, was used in conjunction with these data and field collected geographical locations of the avian species to identify the factors influencing habitat preference of the different bird species and their suitable habitats. Results show that distance from different forest patches played a more important role in influencing habitat suitability for the different avian species than local scale factors related to vegetation structure and health. In addition to distance from forest patches, LiDAR‐derived forest structure and Landsat‐derived spectral variables were important determinants of avian habitat preference. The models derived using MaxEnt were used to create an overall habitat suitability map (HSM) which mapped the most suitable habitat patches for sustaining all the avian species. This work also provides insight that retention of forest patches, including degraded and isolated forest patches in addition to large contiguous forest patches, can facilitate bird species retention within tropical agricultural landscapes. It also demonstrates the effective use of RS data in distinguishing between forests that have undergone varying levels of degradation and identifying the habitat preferences of different bird species. Practical conservation management planning endeavors can use such data for both landscape scale monitoring and habitat mapping.  相似文献   

4.
Abstract Most of the original forest and woodland cover on the western slopes of New South Wales and the northern plains of Victoria has been cleared for agriculture (wheat, sheep and cattle) and what remains is highly fragmented and modified by a long history of disturbance. Over the past three decades, native eucalypt trees and shrubs have been planted extensively in a part of this region to provide a range of environmental benefits. Our aim was to determine the extent to which these plantings could improve biological diversity in agricultural landscapes in south‐eastern Australia and to identify the variables influencing their effectiveness. We sampled birds at 120 sites encompassing the range of available patch sizes, stand ages, floristic and structural conditions, and habitat attributes for revegetated areas and remnants of native vegetation, and we compared these to nearby paddocks. Eucalypt plantings were found to provide significant improvements in bird population density compared with cleared or sparsely treed paddocks, and mixed eucalypt and shrub plantings had similar bird communities to remnant native forest and woodland in the region. Birds displayed a strong response to patch size, with both larger (≥5–20 ha) eucalypt plantings and larger (≥5–20 ha) remnants having more species and more individuals per unit area than smaller (<5 ha) patches of these vegetation types. Older (10–25 years) plantings had more bird species and individuals than young (<10 years) plantings. The distance from remnant forest and woodland (habitat connectivity) appeared to be an important variable influencing bird species richness in eucalypt plantings. The main differences were due to the greater numbers of species classified as woodland‐dependent in the larger‐sized patches of plantings and remnants. Eucalypt plantings provided useful habitat for at least 10 declining woodland‐dependent species, notably for the Speckled Warbler, Red‐capped Robin and Rufous Whistler. The Brown Treecreeper and Dusky Woodswallow appeared to be the species most limited by the extent of remnant forest and woodland in the region. Plantings of all shapes and sizes, especially those larger than 5 ha, have an important role to play in providing habitat for many bird species. Restoration efforts are more likely to be successful if eucalypt plantings are established near existing remnant vegetation.  相似文献   

5.
Aim A common strategy for conserving biodiversity in fire‐prone environments is to maintain a diversity of post‐fire age classes at the landscape scale, under the assumption that ‘pyrodiversity begets biodiversity’. Another strategy is to maintain extensive areas of a particular seral state regarded as vital for the persistence of threatened species, under the assumption that this will also cater for the habitat needs of other species. We investigated the likely effects of these strategies on bird assemblages in tree mallee vegetation, characterized by multi‐stemmed Eucalyptus species, where both strategies are currently employed. Location The semi‐arid Murray Mallee region of south‐eastern Australia. Methods We systematically surveyed birds in 26 landscapes (each 4‐km diameter), selected to represent gradients in the diversity of fire age classes and the proportion of older vegetation (> 35 years since fire). Additional variables were measured to represent underlying vegetation‐ or fire‐mediated properties of the landscape, as well as its biogeographic context. We used an information‐theoretic approach to investigate the relationships between these predictor variables and the species richness of birds (total species, threatened species and rare species). Results Species richness of birds was not strongly associated with fire‐mediated heterogeneity. Species richness was associated with increasing amounts of older vegetation in landscapes, but not with the proportion of recently burned vegetation in landscapes. Main conclusions The preference of many mallee birds for older vegetation highlights the risk of a blanket application of the ‘pyrodiversity begets biodiversity’ paradigm. If application of this paradigm involved converting large areas from long unburned to recently burned vegetation to increase fire‐mediated heterogeneity in tree mallee landscapes, our findings suggest that this could threaten birds. This research highlights the value of adopting a landscape‐scale perspective when evaluating the utility of fire‐management strategies intended to benefit biodiversity.  相似文献   

6.
HUW LLOYD 《Ibis》2008,150(4):735-745
Habitat restoration strategies for fragmented high Andean forest landscapes must consider the influence of within‐patch habitat quality on bird abundance. I examined vegetation and bird abundance at three locations within a highly fragmented Polylepis forest landscape in the Cordillera Vilcanota, southern Peru. Across the landscape, there was significant variation in the vegetation structure of Polylepis forest patches of different size categories, especially in terms of tree girth, tree height, tree density, and canopy vegetation structure. Principal Component Analysis extracted five factors of habitat quality, which together accounted for 74.2% of the variability within 15 habitat variables. Polylepis bird species differed in their responses to habitat quality but, overall, variation in Polylepis bird abundance was not fully captured by the range of habitat quality variables. Tall, dense vegetation cover was clearly important for 11 conservation‐important species, a high density of large trees was important for 10 species and primary forest ground cover was important for eight species. Habitat quality exhibited no significant influence on the abundance of only one species –Asthenes urubambensis. The abundance of seven species was associated with lower elevation forest, but only one species was associated with higher elevation forest. Management of habitat quality in large and medium remnant forest patches throughout the Cordillera Vilcanota, particularly in the 3800–4200 m elevation range, will be a cornerstone in ensuring the persistence of the majority of conservation‐important bird species populations.  相似文献   

7.
Short‐rotation woody cropping (SRWC) refers to silvicultural systems designed to produce woody biomass using short harvest cycles (1–15 years), intensive silvicultural techniques, high‐yielding varieties, and often coppice regeneration. Recent emphasis on alternatives to fossil fuels has spurred interest in producing SRWC on privately owned and intensively managed forests of North America. We examined potential bird and small mammal response at the stand level to conversion of existing, intensively managed forests to SRWCs using meta‐analysis of existing studies. We found 257 effect sizes for birds (243 effect sizes) and mammals (14 effect sizes) from 8 studies involving Populus spp. plantations. Diversity and abundance of bird guilds were lower on short‐rotation plantations compared with reference woodlands, while abundance of individual bird species was more variable and not consistently higher or lower on SRWC plantations. Shrub‐associated birds were more abundant on SRWC plantations, but forest‐associated and cavity‐nesting birds were less abundant. Effects on birds appeared to decrease with age of the SRWC plantation, but plantation age was also confounded with variation in the type of reference forest used for comparison. Both guilds and species of mammals were less abundant on SRWC plantations. These conclusions are tentative because none of these studies directly compared SRWC plantations to intensively managed forests. Plantations of SRWCs could contribute to overall landscape diversity in forest‐dominated landscapes by providing shrubby habitat structure for nonforest species. However, extensive conversion of mature or intensively managed forests to SRWC would likely decrease overall diversity, especially if they replace habitat types of high conservation value.  相似文献   

8.
ABSTRACT To clarify the underlying causes of the species‐area relationship in marsh‐nesting birds, I studied eight freshwater tidal marshes of the Connecticut River that differed in area, degree of isolation, mudflat cover, water cover, tidal regime, and extent of individual plant communities. I measured these habitat variables on aerial infrared photos, and surveyed bird populations by mapping the distribution of all birds in marshes under 5 ha in area and establishing 50‐m radius plots in marshes over 5 ha. From surveys, I determined species richness, population densities, and total populations. Analysis revealed a positive relationship between species richness and area, but no correlation between area and habitat heterogeneity. Other habitat variables were poor predictors of species richness. The lack of a relationship between habitat and species richness appeared to be a consequence of most vegetation types present not being sufficiently distinct for birds to differentially associate with them. I also found no relationship between bird population density and area, suggesting that habitat quality in marshes did not improve with increasing size, and species evenness declined with increasing richness because greater richness was associated with the presence of more rare species. Larger marshes had more rare species, species with larger populations, and species with a minimum threshold area for occurrence. Thus, my results are consistent with theoretical predictions that larger populations are less prone to local extinction and, as individuals are added to a community, more rare species are present.  相似文献   

9.
Few studies have found strong evidence to suggest that ecotones promote species richness and diversity. In this study we examine the responses of a high‐Andean bird community to changes in vegetation and topographical characteristics across an Andean tree‐line ecotone and adjacent cloud forest and puna grassland vegetation in southern Peru. Over a 6‐month period, birds and vegetation were surveyed using a 100 m fixed‐width Distance Sampling point count method. Vegetation analyses revealed that the tree‐line ecotone represented a distinctive high‐Andean vegetation community that was easily differentiated from the adjacent cloud forest and puna grassland based on changes in tree‐size characteristics and vegetation cover. Bird community composition was strongly seasonal and influenced by a pool of bird species from a wider elevational gradient. There were also clear differences in bird community measures between tree‐line vegetation, cloud forest and puna grassland with species turnover (β‐diversity) most pronounced at the tree‐line. Canonical Correspondence Analysis revealed that the majority of the 81 bird species were associated with tree‐line vegetation. Categorizing patterns of relative abundance of the 42 most common species revealed that the tree‐line ecotone was composed primarily of cloud forest specialists and habitat generalists, with very few species from the puna grassland. Only two species, Thlypopsis ruficeps and Anairetes parulus, both widespread Andean species more typical of montane woodland vegetation edges, were categorized as ecotone specialists. However, our findings were influenced by significant differences in species detectability between all three vegetation communities. Our study highlights the importance of examining ecotones at an appropriate spatial and temporal scale. Selecting a suitable distance between sampling points based on the detection probabilities of the target bird species is essential to obtain an unbiased picture of how ecotones influence avian richness and diversity.  相似文献   

10.
The conservation of biodiversity within tropical forest regions does not lie only in the maintenance of natural forest areas, but on conservation strategies directed toward agricultural land types within which they are embedded. This study investigated variations in bird assemblages of different functional groups of forest‐dependent birds in three agricultural land types, relative to distance from the interior of 34 tropical forest patches of varying sizes. Point counts were used to sample birds at each study site visited. Data from counts were used to estimate species richness, species evenness, and Simpson's diversity of birds. Mean species richness, evenness, and diversity were modeled as responses and as a function of agricultural land type, distance from the forest interior and three site‐scale vegetation covariates (density of large trees, fruiting trees, and patch size) using generalized linear mixed‐effect models. Mean observed species richness of birds varied significantly within habitat types. Mean observed species richness was highest in forest interior sites while sites located in farm centers recorded the lowest mean species richness. Species richness of forest specialists was strongly influenced by the type of agricultural land use. Fallow lands, density of large trees, and patch size strongly positively influenced forest specialists. Insectivorous and frugivorous birds were more species‐rich in fallow lands while monoculture plantations favored nectarivorous birds. Our results suggest that poor agricultural practices can lead to population declines of forest‐dependent birds particularly specialist species. Conservation actions should include proper land use management that ensures heterogeneity through retention of native tree species on farms in tropical forest‐agriculture landscapes.  相似文献   

11.
Large‐bodied frugivorous birds play an important role in dispersing large‐sized seeds in Neotropical rain forests, thereby maintaining tree species richness and diversity. Conversion of contiguous forest land to forest fragments is thought to be driving population declines in large‐bodied frugivores, but the mechanistic drivers of this decline remain poorly understood. To assess the importance of fragment‐level versus local landscape attributes in influencing the species richness of large‐bodied (>100 g) frugivorous birds, we surveyed 15 focal species in 22 forest fragments (2.7 to 33.6 ha, avg. = 16.0 ha) in northwest Ecuador in 2014. Fragment habitat variables included density of large trees, canopy openness and height, and fragment size; landscape variables included elevation and the proportion of tree cover within a 1 km radius of each fragment. At both the individual species level, and across the community of 12 species of avian frugivore we detected, there was higher richness and probability of presence in fragments with more tree cover on surrounding land. This tendency was particularly pronounced among some endangered species. These findings corroborate the idea that partially forested land surrounding fragments may effectively increase the suitable habitat for forest‐dwelling frugivorous birds in fragmented landscapes. These results can help guide conservation priorities within fragmented landscapes, with particular reference to retaining trees and reforesting to attain high levels of tree cover in areas between forest patches.  相似文献   

12.
The boreal forest is one of the North America’s most important breeding areas for ducks, but information about the nesting ecology of ducks in the region is limited. We collected microhabitat data related to vegetation structure and composition at 157 duck nests and paired random locations in Alberta’s boreal forest region from 2016 to 2018. We identified fine‐scale vegetation features selected by ducks for all nests, between nesting guilds, and among five species using conditional logistic regression. Ducks in the boreal forest selected nest sites with greater overhead and graminoid cover, but less forb cover than random sites. Characteristics of the nest sites of upland‐ and overwater‐nesting guilds differed, with species nesting in upland habitat selecting nests that provided greater shrub cover and less lateral concealment and species nesting over water selecting nests with less shrub cover. We examined the characteristics of nest sites of American Wigeon (Mareca americana), Blue‐winged Teal (Spatula discors), Green‐winged Teal (Anas crecca), Mallards (Anas platyrhynchos), and Ring‐necked Ducks (Aythya collaris), and found differences among species that may facilitate species coexistence at a regional scale. Our results suggest that females of species nesting in upland habitat selected nest sites that optimized concealment from aerial predators while also allowing detection of and escape from terrestrial predators. Consequently, alteration in the composition and heterogeneity of vegetation and predator communities caused by climate change and industrial development in the boreal forest of Canada may affect the nest‐site selection strategies of boreal ducks.  相似文献   

13.
The post‐fledging period is a critical life stage for young grassland birds. Habitat selection by recently fledged birds may differ from that of adults and may change as juveniles transition from the care and protection of parents to independence. To describe patterns of habitat selection during these important life stages, we studied habitat use by juvenile Grasshopper Sparrows (Ammodramus savannarum) in a Conservation Reserve Program grassland in Maryland. We used radio‐telemetry to track daily movement patterns of two age classes of Grasshopper Sparrows during the post‐fledging period. Sparrows were classified as either dependent (<32‐d‐old) or independent (≥32‐d‐old). We characterized the vegetation at 780 vegetation plots (390 plots where birds were located and 390 paired random plots). Microhabitats where dependent birds were found had significantly more bare ground, litter, and plant species richness than paired random plots. In addition, dependent birds were found in plots with less bare ground, more warm‐season grass cover, more total vegetation cover, and more forb cover than plots used by independent birds. Plots where independent birds were located also had significantly more bare ground than random plots. Dependent birds are less able to escape from predators because their flight feathers are not fully grown so they may benefit from remaining in areas of greater vegetation cover. However, juveniles transitioning from dependence to independence must forage on their own, possibly explaining their increased use of more open areas where foraging may be easier. To properly manage habitat for grassland birds, management strategies must consider the changing needs of birds during different stages of development. Our results highlight the importance of diverse grassland ecosystems for juvenile grassland birds during the transition to independence.  相似文献   

14.
Variation in grassland vegetation structure influences the habitat selection of insectivorous birds. This variation presents a trade‐off for insectivorous predators: Arthropod abundance increases with vegetation height and heterogeneity, but access to arthropod prey items decreases. In contrast, grazing by large herbivores reduces and homogenizes vegetation, decreasing total arthropod abundance and diversity. However, the presence of livestock dung may help counteract the overall reduction in invertebrates by increasing arthropods associated with dung. It is unclear, however, how the presence of arthropod prey in dung contributes to overall habitat selection for insectivorous birds or how dung‐associated arthropods affect trade‐offs between vegetation structure, arthropod abundance, and access to prey. To explore these relationships, we studied habitat selection of the Black‐necked Crane (Grus nigricollis), a large omnivorous bird that breeds on the Qinghai–Tibet Plateau. We assessed the relationships between habitat selection of cranes and vegetation structure, arthropod abundance, and the presence of yak dung. We found that Black‐necked Cranes disproportionately foraged in grassland patches with short sward height, low sward height heterogeneity, and high numbers of dry yak dung, despite these habitats having lower total arthropod abundance. Although total arthropod abundance is lower, these habitats are supplemented with dry yak dung, which are associated with coleopteran larvae, making dung pats an indicator of food resources for breeding Black‐necked Cranes. Coleopteran adults and larvae in yak dung appear to be an important factor influencing the habitat selection of Black‐necked Cranes and should be considered when assessing grassland foraging trade‐offs of insectivorous birds. This research provides new insights into the role of livestock dung in defining foraging habitats and resources for insectivorous predators.  相似文献   

15.
Bird communities composed of habitat specialists suffer considerable loss of species following disturbance (Ecol. Monogr. 41 , 1971, 207–233). Participatory forest management (PFM) aims to ensure local ownership and support for forest conservation. This study determined if forest birds and forest quality in places under PFM is significantly higher than areas without PFM in Arabuko‐Sokoke forest. Forest quality data were collected in the PFM and no PFM zones in the Mixed forest (MF) and Cynometra Woodland (CW). Plot‐based approach was used to collect vegetation data along 1 km transects at intervals of 1 km sampling twenty transects and 200 plots in each of the study zones. Birds’ data were collected using 10‐min point‐counts along 88, 1 km long transects placed 1‐km apart sampling in 30 m radius‐plots at intervals of 100 m. Data were collected in 2008 and 2009. The results showed higher measures of forest quality in PFM zones than no PFM zones which showed higher measures of forest disturbance. The results did not show statistical differences in birds’ diversity indexes between PFM and no PFM zones indicating that the human‐induced disturbance has not reached critical ecological thresholds to affect birds’ species diversity. It can be deduced that PFM investment is leading to improved forest management.  相似文献   

16.
ABSTRACT Across the Neotropics, small‐bodied terrestrial insectivores are sensitive to forest fragmentation and are largely absent from second‐growth forests. Despite their sensitivity to forest structure, the microhabitat relationships of these birds have not been quantified. From July 1994 to January 1995 in central Amazonia, we characterized habitat at sites where nine species of terrestrial insectivores were observed foraging, as well as at randomly selected sites in continuous forest and two types of 10–15‐yr‐old second‐growth forest common in Amazonia (Vismia‐ and Cecropia‐dominated). We used factor analysis to find suites of correlated variables. From each factor, we selected a representative variable that was relatively easy to measure. We used Bayesian analysis to estimate means and standard deviations of these variables for each species and for each type of habitat. All nine focal species were associated with ranges of microhabitat variables, such as leaf litter depth and tree densities, often absent in second‐growth forests. At least in the early stages of regeneration, neither type of second‐growth forest provides suitable structure for the terrestrial insectivores in our study. The large leaves of Cecropia trees that make up the thick leaf litter may preclude the use of Cecropia‐dominated second growth by our focal species, many of which manipulate leaves when foraging. The leaf litter in Vismia‐dominated second growth was also thicker than sites used for foraging by our focal species. In addition, Vismia‐dominated growth had more small trees and small nonwoody vegetation, perhaps impeding movement by terrestrial birds. In continuous forest, our focal species foraged in microhabitats with characteristics that generally overlapped those of randomly selected sites. Thus, our results are consistent with the hypothesis that microhabitat differences make second‐growth forests unsuitable for our focal species.  相似文献   

17.
Abstract The distributions of lizards across habitat edges delimiting open‐forest and regenerating sand‐mined areas as a function of distance from the edge were studied at Tomago, New South Wales, Australia. Pitfall‐trapping was used to survey lizards across the northern edges of four forest fragments, to determine if lizards displayed characteristic responses across the edge, and whether these could be explained by the different habitat conditions. At each site, 11 equally spaced drift fences (each parallel to the edge) were arranged in a transect running perpendicular to the edge, and stretching 50 m into each habitat type. Captures of Amphibolurus muricatus (Agamidae) decreased substantially across the edge from the mine‐path to the forest so that it was identified as a mine‐path specialist lizard species. Captures of two skink species decreased across the mine‐path before reaching the edge, and were not caught (Ctenotus taeniolatus) or were seldom caught (Ctenotus robustus) in the forest, so they were identified as mine‐path specialist, edge avoiding, lizard species. Captures of Lampropholis delicata (Scincidae) increased across edges into the forest, consistent with the expectation for a forest specialist. Regression analyses indicated the responses to edges of three lizard species (A. muricatus, C. robustus and C. taeniolatus) were negatively correlated with canopy cover (probably due to its influence on temperature, as captures of A. muricatus and C. robustus were also correlated positively with mean daily temperature). In addition, the response of C. robustus correlated negatively with a vegetation factor (dense, even vegetation in the first 50 cm from ground level). The response of L. delicata correlated positively with understorey height. We have identified edge response strategies for four species of lizards across edges delimiting temperate open‐forest and mined areas, and identified habitat and microclimate variables that may have driven these responses.  相似文献   

18.
Species occurrence is influenced by a range of factors including habitat attributes, climate, weather, and human landscape modification. These drivers are likely to interact, but their effects are frequently quantified independently. Here, we report the results of a 13‐year study of temperate woodland birds in south‐eastern Australia to quantify how different‐sized birds respond to the interacting effects of: (a) short‐term weather (rainfall and temperature in the 12 months preceding our surveys), (b) long‐term climate (average rainfall and maximum and minimum temperatures over the period 1970–2014), and (c) broad structural forms of vegetation (old‐growth woodland, regrowth woodland, and restoration plantings). We uncovered significant interactions between bird body size, vegetation type, climate, and weather. High short‐term rainfall was associated with decreased occurrence of large birds in old‐growth and regrowth woodland, but not in restoration plantings. Conversely, small bird occurrence peaked in wet years, but this effect was most pronounced in locations with a history of high rainfall, and was actually reversed (peak occurrence in dry years) in restoration plantings in dry climates. The occurrence of small birds was depressed—and large birds elevated—in hot years, except in restoration plantings which supported few large birds under these circumstances. Our investigation suggests that different mechanisms may underpin contrasting responses of small and large birds to the interacting effects of climate, weather, and vegetation type. A diversity of vegetation cover is needed across a landscape to promote the occurrence of different‐sized bird species in agriculture‐dominated landscapes, particularly under variable weather conditions. Climate change is predicted to lead to widespread drying of our study region, and restoration plantings—especially currently climatically wet areas—may become critically important for conserving bird species, particularly small‐bodied taxa.  相似文献   

19.
In Europe, the consequences of commercial plantation management for birds of conservation concern are poorly understood. The European Nightjar Caprimulgus europaeus is a species of conservation concern across Europe due to population depletion through habitat loss. Pine plantation‐forest is now a key Nightjar nesting habitat, particularly in northwestern Europe, and increased understanding of foraging habitat selection is required. We radiotracked 31 Nightjars in an extensive (185‐km2) complex conifer plantation landscape in 2009 and 2010. Home‐range 95% kernels for females, paired males and unpaired males were an order of magnitude larger than song territories of paired males, emphasizing the importance of habitats beyond the song territory. Nightjars travelled a mean maximum distance of 747 m from the territory centre each night. Home‐range placement relative to landscape composition was examined by compositional analysis. Pre‐closure canopy forest (aged 5–10 years) was selected at all scales (MCP, 95% and 50% kernels), with newly planted forest (aged 0–4 years) also selected within 50% kernels. For telemetry fixes relative to habitat composition within 2 km of their territory centre, individuals again selected pre‐closure and newly planted forest, and also grazed grass heath. Open ungrazed habitat was not selected, with implications for open habitat planning for biodiversity conservation within public‐owned forests. Despite the Nightjars’ selection for younger growth, moth biomass was greater in older forest stands, suggesting that foraging site selection reflects ease of prey capture rather than prey abundance. Within large plantation‐forest landscapes, a variety of growth stages is important for this species and our results suggest that grazing of open habitats within and adjacent to forest will additionally benefit the European Nightjar.  相似文献   

20.
Abstract Fine‐scale habitat preferences of three co‐occurring mycophagous mammals were examined in a tropical wet sclerophyll forest community in north‐eastern Australia. Two of the three mammal species responded to fine‐scale variation in vegetation and landform around individual trap locations. At a broad scale, the northern bettong (Bettongia tropica), an endangered marsupial endemic to the Australian wet tropics region, showed a preference for ridges over mid‐slopes and gullies, irrespective of forest type. In contrast, the northern brown bandicoot (Isoodon macrourus), a widespread marsupial, displayed a preference for Eucalyptus woodland over adjacent Allocasuarina forest, irrespective of topographic category. The giant white‐tailed rat (Uromys caudimaculatus), a rodent endemic to the wet tropics, showed no particular preference for either forest type or topographic category. A multiple regression model of mammal capture success against three principal habitat gradients constructed from 21 habitat variables using principal component analysis indicated strong species‐specific preferences for fine‐scale vegetation assemblages. Bettongs preferred areas of Eucalyptus woodland with sparse ground cover, low densities of certain grass species, high density of tree stems and few pig diggings. Bandicoots, in contrast, favoured areas in both forest types with dense ground cover, fewer tree stems and greater numbers of pig diggings; that is, characteristics least favoured by bettongs. The striking differences in fine‐scale habitat preferences of these two mammals of similar body size and broad habitat requirements suggest a high degree of fine‐scale habitat partitioning. White‐tailed rats did not show preference for any of the habitat gradients examined.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号