Avian Community Structure Research Articles

Shifts in vegetation and avian community structure following the decline of a foundational forest species, the eastern hemlock

Eastern hemlock (Tsuga canadensis) is undergoing widespread decline throughout the eastern United States due to the introduction of the nonnative hemlock woolly adelgid (Adelges tsugae). In light of hemlock's unique significance for avian communities, we examined the long-term response of the breeding bird community to the decline and die-off of this foundational forest species. We conducted variable-radius point counts to survey bird communities in both hemlock and hardwood stands in 2000, during the early stages of adelgid infestation, and again in 2015 and 2016, following significant hemlock decline. We also measured the severity of hemlock decline and associated vegetation variables in the same hemlock stands in which avian surveys were completed. We used multispecies occupancy models to examine species-specific and species group responses to hemlock decline. Results showed that, across hemlock stands, hemlock basal area declined from a mean of 56% of the total basal area to 46%, and that hemlock decline was correlated with current vegetation structure, including an increased deciduous understory. Species richness of hemlock-associated birds declined by an average of ∼1 species per survey location. The Black-throated Green Warbler (Setophaga virens) was the most strongly affected, declining in occupancy by 30%. All other species groups responded positively, with the strongest responses by species associated with the shrub layer, forest edge, and mature deciduous habitat. The species composition in hemlock and hardwood stands became more similar over time as the unique species assemblages in hemlock stands gave way to the avian community of the surrounding hardwood landscape, highlighting a trend toward homogenization of the avian community. Where hemlock-associated bird species persisted, their presence was correlated with a combined effect of greater hemlock basal area and better hemlock condition. Our results demonstrate that the decline of hemlocks has restructured vegetation communities and their associated avian communities over time, with strong implications for forest-specialist birds.

Avian Community Structure as a Function of Season, Habitat Type, and Disturbance, in Mole National Park, Northern Region (Ghana)

The study assessed factors that influenced bird-habitat preference, diversity, and spatial distribution in Mole National Park. Birds were identified using point count sampling method, while ordination techniques were performed to determine the influence of environmental factors on bird-habitat preference. A total of 4951 individuals belonging to 131 species were identified across the four habitat types in the wet (n= 3033) and dry (n= 1648) seasons. Despite the high abundance and richness of birds in the woodland and shrubland habitats, grassland habitat was the most diverse, due to the high spatial evenness distribution of the birds. Bushfire, patchiness, and animal trampling were the key environmental determinants in bird assemblages and habitat preferences and accounted for 62.02% and 81.82% variations in the two seasons. Rarer birds like White-Backed Vulture (NT) and White-Headed Vulture (CR), Bateleur Eagle (NT), and Woolly-Necked Stork (VU), with high conservation concern, suggest intensification of conservation effort, while the dominance of Sahel Bush-sparrow was probably due to their broad range habitat preferences and ability to adapt to environmental conditions across these habitats. These species could be used as indicators of habitat quality, if future scenarios restrict their movement or distribution in narrow range habitats.

Road induced edge effects on a forest bird community in tropical Asia

BackgroundEdge effects cause changes in bird community richness, abundance, and/or distribution within a landscape, but the avian guilds most influenced can vary among regions. Although Southeast Asia has the highest rates of deforestation and projected species loss, and is currently undergoing an explosive growth in road infrastructure, there have been few studies of the effects of forest edges on avian communities in this region.MethodsWe examined avian community structure in a dry evergreen forest in northeastern Thailand adjacent to a five-lane highway. We evaluated the richness and abundance of birds in 11 guilds at 24 survey points on three parallel transects perpendicular to the edge. At each point, 10-min surveys were conducted during February‒August 2014 and March‒August 2015. Vegetation measurements were conducted at 16 of the bird survey points and ambient noise was measured at all 24 survey points.ResultsWe found a strongly negative response to the forest edge for bark-gleaning, sallying, terrestrial, and understory insectivores and a weakly negative response for arboreal frugivore-insectivores, foliage gleaning insectivores, and raptors. Densities of trees and the percentage canopy cover were higher in the interior, and the ambient noise was lower. In contrast, arboreal nectarivore-insectivores responded positively to the forest edge, where there was a higher vegetation cover in the ground layer, a lower tree density, and a higher level of ambient noise.ConclusionPlanners should avoid road development in forests of high conservation value to reduce impacts on biodiversity. Where avoidance is impossible, a number of potential mitigation methods are available, but more detailed assessments of these are needed before they are applied in this region.

Seasonal changes in acoustic detection of forest birds

Autonomous recording is commonly used to examine the structure of avian communities in a variety of landscapes. Many birds return to the breeding grounds in May yet acoustic surveys typically begin in June. In many species, singing activity declines through the breeding season and so detections may be lower later in the season. The aim of our study was to compare the species richness and the community composition measured early (mid-late May) and later (mid-late June) in the breeding season. We recorded the community of singing birds at 13 locations in York Region, Ontario, Canada woodlots over two days using autonomous recorders. We used spectrographic analysis to scan recordings and identify all vocalizing species. We found that species richness was significantly higher in early recordings compared to later recordings with detections of both migrants and residents displaying this trend. Most food and foraging guilds were also detected significantly less often later in the season. Despite changes in species richness, the proportion of the community represented by each foraging guild did not vary between early and late recordings. Our results suggest that acoustic recordings could be collected earlier in the breeding season, extending the survey period into May. If the primary goal of monitoring is to document species presence/absence then earlier recordings may be advantageous.

中国城市鸟类学研究进展

PDF HTML阅读 XML下载 导出引用 引用提醒 中国城市鸟类学研究进展 DOI: 10.5846/stxb201703290546 作者: 作者单位: 北京师范大学地表过程与资源生态国家重点实验室，人与环境系统可持续研究中心，北京，100875,北京师范大学地表过程与资源生态国家重点实验室，人与环境系统可持续研究中心，北京，100875 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金面上项目（31670702）；国家青年基金项目（41301645）；基于热环境改善的城市绿地系统降减细颗粒物（PM2.5）质量浓度的研究——以北京为例（编号31570699） Urban ornithological research in China: A review Author: Affiliation: Center for Human-Environment System Sustainability (CHESS), State Key Laboratory of Earth Surface Processes and Resource Ecology (ESPRE), Beijing Normal University, Beijing, 100875, China,Center for Human-Environment System Sustainability (CHESS), State Key Laboratory of Earth Surface Processes and Resource Ecology (ESPRE), Beijing Normal University, Beijing, 100875, China Fund Project: The National Science Fund for Distinguished Young Scholars 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:我国的城市鸟类学起步于20世纪80年代，随着城市化过程的加速，城市鸟类学也有了较快发展。为了全面系统地了解中国城市鸟类学研究的历史、现状与发展趋势，在中国期刊全文数据库中以"城市"和"鸟类"为主题词检索了1950-2015年间发表的文章，筛选获得128篇文章，并对检索结果进行综述。结果显示，城市鸟类学发表文章数量自20世纪80年代起逐渐增加，由1981-1990的年均0.7篇跃升至2011-2015年的年均11.6篇。研究地涉及全国29个省级行政区的57个城市。研究的主要议题包括：城市鸟类的群落结构和分布、影响城市鸟类的主要环境因素和城市鸟类的保护实践。综述发现，不同城市环带位置，城市中不同生境组合会影响城市的鸟类群落结构；不同尺度上的环境因素会对鸟类的分布、繁殖、觅食和生理情况产生多种影响，而城市化是影响这些环境因素的主要驱动力；鸟类栖息地规划以保护城市中自然栖息地，增加其景观连通性促进鸟类保护，鸟类招引技术主要通过补充巢资源和食物资源促进鸟类保护。然而，由于资源限制，有关城市鸟类的长期研究相对较少。并且，已有研究中城市鸟类的生态系统服务也鲜有涉及。为此，对我国城市鸟类学的发展提出了三点展望，城市鸟类学研究应加强城市绿地鸟类招引措施的生态影响研究，进一步发掘城市鸟类的自然体验与环境教育价值，并促进民间爱好者参与长期系统性城市鸟类学调查。 Abstract:In China, urban ornithological research started as early as the 1980s and developed rapidly with the fast urbanization process. In order to better understand the history and recent trends of urban ornithological research in China, we conducted a systematic review. We used the key words of "urban" and "birds" to search for scientific articles published during 1950-2015 in the "China National Knowledge Infrastructure" database and retrieved 128 articles. Based on our review, we summarized the history and recent trends in publication, main research topics and major findings in urban ornithology studies. The urban ornithology publications increased from an annual average of 0.7 ariticle during 1981-1990 to 11.6 articles during 2011-2015. The research areas include 57 cities located in 29 provinces. The topic of urban ornithology studies includes research of urban avian community structure and distribution, effect of environment factors on urban birds, and practices of urban avian conservation. Major findings include:(1) the urban-rural gradient and different habitat groups would affect avian community structure;(2) environmental factors at different scales had a variety of effects on distribution, breeding, feeding, and physiological conditions of urban birds; and(3) habitat conservation in urban areas and bird attracting measurements, such as setting feeders, contributed to urban avian conservation. However, limited by resources long-term study on urban avian is rare. In addition, very few of studies examined the ecosystem services provided by avian fauna in the urban context. In the future, we suggest researchers pay more attention to(1) the ecological effect of the bird attracting measures,(2)the value of natural experience and environmental education brought by the urban avian fauna, and work with birdwatchers to design long-term urban avian researches. 参考文献 相似文献 引证文献

Structure of avian communities in lowland coniferous forests in Opole Silesia (SSW Poland)

Abstract In Poland, forests comprise 31% of the total surface area, while the lowland coniferous forests comprise 51% of 94 000 km2 afforested areas. The line transect method was employed in 2002 and 2004 to estimate population densities and dominance of all bird species breeding in a selected fragment of such forest (eight transects with 165 sections and 77.7 km in total length). In total, 54 breeding bird species were recorded. The numbers varied between 37 and 44 on the particular transect. The number of breeding pairs per 10 ha varied on each transect from 41.0 to 93.6 (x=64.8; SD=102.22). Shannon’s diversity index varied between 1.2 and 1.4 on particular transects, while Simpson’s diversity index varied between 0.7 and 0.9. Also Pieleau’s evenness index varied slightly between 0.05 and 0.07. In overall, the differences between densities of breeding species on 8 transects were not statistically significant. The Chaffinch Fringilla coelebs was by far the most numerous bird species, recorded as eudominant in all eight transects and present in all 165 sections. The second to the Chaffinch was the Chiffchaff Phylloscopus collybita; also recorded in all sections and as a dominant in all transects. Three other species, namely the Blackbird Turdus merula, Willow Warbler Phylloscopus trochilus and Blackcap Sylvia atricapilla were recorded each one in more than 90% sections (N=165), and on particular transects their dominance varied between 4 and 11%. Residents comprised 57.5% of all breeding pairs. Short-distance migrants were almost twice more common than long-distance migrants. Insectivores were by far the most numerous feeding guild represented 88.9% of all breeding pairs. Overall density, cumulative dominance, diversity and evenness were unexpectedly very similar in this study (managed forest) and in natural primeval lowland coniferous forests of Białowieża.

Behavioral Differences among Eastern Bluebird Populations Could Be a Consequence of Tree Swallow Presence: A Pilot Study

Aggressive interference competition for limited resources is frequently observed among animals. However, these behavioral interactions within (intraspecific) and between (interspecific) species are costly as they can be energetically expensive and cause injury or death. To avoid these agonistic interactions, numerous species alter their behaviors and resource requirements. Spatial variation in nest site competition allows for investigation of concurrent variation in territorial defense behavior. Further, among species with bi-parental nest defense, behavioral similarity in territorial defense may benefit pairs. Here, we studied territorial aggression between two eastern bluebird (Sialia sialis) populations (North Carolina and Alabama, USA) that differ in avian community structure; those in North Carolina have recently begun to experience strong interspecific competition for nesting cavities by tree swallows (Tachycineta bicolor), a competitive pressure that is relatively new for North Carolina bluebirds (~35-40 years) and is absent in Alabama populations. We found that bluebirds in North Carolina are more aggressive to simulated territorial intrusions compared to their Alabama counterparts. Behavioral similarity (here, in aggression) between partners is strong and similar in both populations. These results suggest that bluebirds in North Carolina may have to maintain higher baseline aggression during territory establishment and nest construction to co-occur with highly aggressive tree swallows, but that, in both populations, behavioral similarity between partners may be adaptive. Finally, we acknowledge the preliminary nature of this study and the need for expanding the behavioral studies to other sites in the southeastern United States. Greater regional coverage would exclude the possibility of alternative drivers of the observed behavioral differences between the North Carolina and Alabama populations.

Ecomorphological structure of avian communities changes upon arrival of wintering species

Community composition reflects evolutionary and ecological processes such as diversification and species assortment. Communities are generally considered to be saturated, which means that the number of species is maximized and that regulatory mechanisms, such as interspecific competition, prevent the addition of new species. In the tropics, however, species numbers of local bird assemblages double up each winter after the arrival of migratory species, which suggests that a rearrangement of niches occurs. Here ecological space is defined by morphological traits that reflect the ecological position of species, to describe changes in the structure of local communities. We found that the average morphological distance between species was reduced, and the volume (the total extent of trait space) was expanded with the arrival of migrants, indicating that newcomers occupy the periphery and the interior of the available ecological space. Furthermore, with greater morphological differences between resident species, higher numbers of migratory species can take advantage of free space and potentially exploit unused resources due to their intermediate morphology. We highlight the differences in the attributes of resident versus migratory species that may allow both to be accommodated in the morphological space, and we suggest coexistence theory as a possible explanation for the co-occurrence of similar species.

Avifaunal community structure associated to El Conchalito mangrove, BCS, Mexico under different tide conditions

The importance in the study of avian community structure relates to their relevant role in theecosystem. Specially, when they are exposed to collateral damage by anthropogenic activities. The goal of thisresearch was to determine the variation of avian community structure in the mangrove forest El Conchalito, BCSthrough the use of ecological indices such as diversity (H’), dominance (D), and the biological value index (IVB)in April-June of 2016 during the seasonal transition from Spring-Summer. To describe the environmental frame,measurements of temperature, noise level, and chlorophyll a were made, and other climatological data were used.A total of 15 species of aquatic, marine or shore birds were recorded (5 orders, 7 families and 9 genera), and 3species of terrestrial birds (2 orders, 2 families and 3 genera). Maximum bird abundances were observed duringthe first sampling. Diversity values varied between H´= 1.1 and H´= 1.8, with maxima at the beginning and atthe end of the study period. This was related with the low tides and the increase of species richness, respectively.Noise level and chlorophyll a concentration, were not associated directly with the changes observed in the community structure. Species richness was associated directly with temperature increase. The most important birdspecies were: Egretta thula (96.9%), Zenaida asiatica (88.7%), Numenius phaeopus (86.8%), and Egretta rufescens (83.8); less important was Ceryle alcyon (28.2). Three species protected under NOM-059-SEMARNAT-2010were identified.

Garden Bird Feeding: Insights and Prospects from a North-South Comparison of This Global Urban Phenomenon

Intentional feeding of wild birds in gardens or backyards is one of the most popular forms of human-wildlife interactions in the developed world, especially in urban environments. Scale and intensity of bird feeding are enormous with mainly birdseed consumed daily by a range of species. This represents a subsidy to natural diets of birds attracted to the feeders and typically involves novel dietary components. Yet, relatively little is known about how it influences the behavior and ecology of the species visiting feeders. In part, research has been hampered by logistical difficulties of working in urban areas but studies have demonstrated powerful influences on behavior and phenology of avian breeding, the spread of disease, and the structure of avian communities. Here, we compare bird feeding between Northern and Southern Hemispheres as a means of exploring how similarities and differences in avian responses might inform knowledge of this global urban phenomenon. We start by tracing its origins to north-western Europe and how its expansion has occurred before considering how geographical differences in feeding practices and attitudes map onto bird feeding ‘on the ground’. We explore some of the major emerging themes of recent interest, including why citizens are motivated to feed birds, whether birds become fully dependent on food supplements, the role of feeding in avian disease transmission, and how feeding changes urban bird communities. By proposing that scientists work in collaboration with the public providing food to birds, we pose key research questions that need to be answered urgently and suggest accompanying experimental approaches to do so. These approaches are essential if we are to improve our understanding of how bird feeding shapes the behavior, ecology, movements, and community structure of urban birds. Our hope is that through such citizen science we will be able to provide advice as to location-relevant practices that should maximise benefits to both urban biodiversity and human wellbeing, and minimise potential adverse impacts. We demonstrate that bird feeding is important for urban biodiversity conservation, community engagement, and in establishing personal connections with nature and their associated benefits.

The bird species diversity in the wintering season is negatively associated with precipitation, tree species diversity and stand density in the Sierra Madre Occidental, Durango, Mexico

Bird migration constitutes a redistribution of bird diversity that radically changes the composition of the bird community worldwide. It comprises about 19% of the world’s bird species. Several studies have indicated that changes in avian community structure and differences in bird richness in different seasons are mainly driven by seasonality and by winter harshness, and that the associated costs increase with the distance involved. Western Mexico is an important wintering area for most passerines that breed in western North America, and that travel long on the long-distance Central and Pacific migration routes. In this study, we examined bird species richness and diversity during the breeding and wintering seasons in the Central Sierra Madre Occidental (SMO), North Durango (Mexico) in relation to i) tree species diversity, ii) tree dimension, iii) forest stand density and site quality, iv) density and dimension of snag trees, and v) various climate variables. The overall aim of the study was to determine how the observed associations between bird species diversity and variables i-v are affected by the season considered (breeding or wintering). The diversity of bird species in the breeding season was not affected by any of the climate and forest stand variables considered. In contrast, bird species diversity in the wintering season was significantly and weakly to moderately associated with climate variables, tree species diversity and stand density, although not with density or dimension of snag trees. Bird species diversity was higher at lower elevations and in drier and warmer locations of the SMO. The association detected is therefore mainly a local migratory phenomenon.

Conservation status, species composition, and distribution of Avian Community in Bhimbandh Wildlife Sanctuary, India

Birds are among the best indicators of environmental changes. Given the significance of birds for conservation planning and environmental assessments, there is a need to develop a better ecological understanding of avian community structure. In southeast Asia, the association among tropical birds with their habitat is poorly studied. To investigate the influence of different habitats on the avifauna, we studied the composition of local bird communities along habitat gradients characterized by environmental factors such as vegetation type and extent of anthropogenic pressure, using the open-radius point count method. This is the first attempt to document the status, composition, and distribution of avifauna in Bhimbandh Wildlife Sanctuary, Bihar, India. A total of 147 avian species belonging to 58 families and 20 orders were recorded during the study. It was found that the forest range Lakhisarai, with 50% of habitat heterogeneity, supports the highest avian density (6,428 individuals/km2) in the sanctuary, whereas the lowest bird density was recorded from the Munger forest range i.e. 3,847 individuals/km2, which also has the least habitat heterogeneity (i.e. 20%). The forest range Dharara (p = 0.006), and habitat categories degraded bamboo forest (p = 0.005) and forest edge with cultivation (p < 0.001) were found to support significantly higher bird diversity.

Edge Effects and Avian Community Structure in a Restored Tallgrass Prairie

ABSTRACT As a consequence of extensive habitat loss and fragmentation, grassland bird populations have declined substantially across much of North America. To assess management strategies for restoring and maintaining suitable habitat for grassland birds, we conducted a four-year survey of grassland-breeding passerines in the restored tallgrass prairies of the Carleton College Cowling Arboretum in Northfield, Minnesota. Between 2010 and 2013, we sampled bird populations weekly during the breeding season in ten adjacent management units that differed in size and spatial configuration. We used principal components analysis (PCA) to compare avian community composition among the units and to examine the association between habitat properties and makeup of the community. The size of a management unit had no effect on the bird community, but there was a strong impact of forest edge on community composition. Management units with less exposure to forest edge had greater abundance of grassland-obligate but not gr...

Bird community responses to afforested eucalyptus plantations in the Argentine pampas

Land-use change driven by human population growth and economic activity will continue to impact both natural habitats and land currently being used for food, fiber, and fuel production. The effects of this conversion on economically important ecological services will in large part depend on how native biodiversity responds to these changes. We investigated how agriculture-related land use change influences the avian community in northeastern Argentina by examining common agricultural land uses (pasture/annual crops, young and mature large-scale eucalyptus plantations, mixed-use farms with citrus, blueberry and small stands of eucalyptus) and remnant native espinal savannas. In this region, afforested eucalyptus plantations represent a new land-use change from the land cover of pasture with intermixed annual crops that has dominated the region. In this mosaic, we used point counts to assess how avian diversity and community structure differed between land uses. Bird species richness was lowest in older plantations and highest in the espinal savanna, with the other land uses having intermediate richness. Abundance trends followed the same pattern, with low overall abundance in the plantations, intermediate levels for pasture/annual crops, and highest abundance in the espinal. Distinct bird community assemblages were strongly associated with each land use, and between young and mature eucalyptus stands. Birds can be useful indicators for biodiversity as a whole, and the depopulated and depauperate avian community within the eucalyptus plantations will likely lead to reduced provision of many ecosystem services in this region if the spatial extent of plantations continues to expand.

Structure of bird communities in eucalyptus plantations: nestedness as a pattern of species distribution.

Replacement of native habitats by tree plantations has increased dramatically in Brazil, resulting in loss of structural components for birds, such as appropriate substrates for foraging and nesting. Tree plantations can also reduce faunal richness and change the composition of bird species. This study evaluated the structure of avian communities in eucalyptus plantations of different ages and in a native forest. We classified species as habitat specialists or generalists, and assessed if the species found in eucalyptus plantations are a subset of the species that occur in the native forest. Forty-one sampling sites were evaluated, with three point counts each, in a native forest and in eucalyptus plantations of four different ages. A total of 71 bird species were identified. Species richness and abundance were higher in the native forest, reflecting the greater heterogeneity of the habitat. The composition of bird species also differed between the native forest and plantations. The species recorded in the plantations represented a subset of the species of the native forest, with a predominance of generalist species. These species are more tolerant of habitat changes and are able to use the plantations. The commercial plantations studied here can serve as a main or occasional habitat for these generalists, especially for those that are semi-dependent on edge and forest. The bird species most affected by silviculture are those that are typical of open grasslands, and those that are highly dependent on well-preserved forests.

Biotic homogenization: Loss of avian functional richness and habitat specialists in disturbed Andean temperate forests

Habitat loss and degradation have the potential to alter the species richness–functional diversity relationship decreasing both species richness and functional richness, and increasing functional biotic homogenization. These anthropogenic disturbances may have strong impacts on species-poor systems with low functional redundancy. We tested the species richness–functional diversity relationship and the potential effects of deforestation and degradation on functional diversity of avian assemblages in a Biodiversity Hotspot, in southern Chile. For 101 sites established across a disturbance gradient, we conducted 505 point-transect surveys to measure avian community structure, 505 vegetation plots to quantify stand-level structure, and measured deforestation at the landscape-level. We used three functional diversity indices for avian assemblages (functional richness, functional evenness, and community-weighted specialization as a measure of functional biotic homogenization). We found a non-saturating relationship between species richness and both functional richness and community-weighted specialization, suggesting low functional redundancy. We also found a non-significant decline of functional evenness indicating that when adding new species to the initial pool, functional redundancy increases slightly. Deforestation led to a decrease in both functional richness and community-weighted specialization, particularly precluding the persistence of specialized species in disturbed forests. Functional evenness did not vary with deforestation suggesting that the regularity of density distribution in filled niche volume may be relatively resilient to disturbance. However, the fact that community-weighted specialization decreased linearly under deforestation serves as evidence of functional biotic homogenization processes (“loser” specialists being replaced by “winner” generalist species) in a Biodiversity Hotspot.

Nationwide trophic cascades: changes in avian community structure driven by ungulates.

In recent decades, many ungulate populations have changed dramatically in abundance, resulting in cascading effects across ecosystems. However, studies of such effects are often limited in their spatial and temporal scope. Here, we contrast multi-species composite population trends of deer-sensitive and deer-tolerant woodland birds at a national scale, across Britain. We highlight the divergent fates of these two groups between 1994 and 2011, and show a striking association between the calculated divergence and a composite population trend of woodland deer. Our results demonstrate the link between changes in deer populations and changes in bird communities. In a period when composite population trends for deer increased by 46%, the community population trend across deer-sensitive birds (those dependent on understory vegetation) declined much more than the community trend for deer-tolerant birds. Our findings suggest that ongoing changes in the populations of herbivorous ungulates in many countries worldwide may help explain patterns of community restructuring at other trophic levels. Ungulate impacts on other taxa may require more consideration by conservation practitioners than they currently receive.

Avian Diversity Along An Altitudinal Gradient In Highveld/Drakensberg Grasslands

Abstract Temperature and rainfall related to altitudinal gradients influence ecological and evolutionary responses of organisms to physical factors. In this study, the line transect method was used during the years 1996–2001 to compare resident (potentially breeding) bird communities in three altitudinal divisions in Highveld/Drakensberg grasslands in Lesotho: lowlands (&lt; 1700 m a. s. l.), foothills (1700–2200 m a. s. l.) and highlands (&gt; 2200 m a. s. l.). In total, 105 resident species were recorded. The total number of species recorded in lowlands was higher than that in highlands and foothills, but this difference was not statistically significant. The highland and foothill did not differ in numbers of species. A group of five species dominated at all three sites, and the proportion of dominant species in relation to the whole assemblage was very similar. The composition of the dominant group (species with more than 5 % of pairs) and the group of species most often encountered (in more than 80 % of transects) was, however, different. Only two species, Cape Canary Serinuscanicollis and Karoo Prinia Priniamaculosa were dominant in all three study areas, and just one species, the Cape Bunting Emberizacapensis, was dominant in two plots. Similarly, only two species, the Cape Turtle-Dove Streptopelia capicola and Cape Canary had a high frequency of occurrence in all three study areas, and two otherspecies, theKaroo Prinia and Cape Bunting — in two study areas. Simpson’s Diversity Index was strikingly the same (S = 0.96) for all three avian assemblages (lowland, foothill and highland) investigated. However, proportions of breeding pairs of some congeneric species were found to change with the altitude. The granivores were more common (44–45 %) in the foothills and highlands than in lowlands (36%), while insectivores were more common in the highlands (50 %) than in foothills and lowlands (36–37 %). In general, avifauna is relatively diverse and unique in the Highveld/Drakensberg grasslands. Results presented here provide data for further investigation of the effect of the supposed climate warming on the diversity and structure of avian communities.

Impact of Environmental and Disturbance Variables on Avian Community Structure along a Gradient of Urbanization in Jamshedpur, India.

Gradient pattern analysis was used to investigate the impact of environmental and disturbance variables on species richness, species diversity, abundance and seasonal variation of birds in and around Jamshedpur, which is one of the fastest growing cities of India. It was observed that avian community structure is highly influenced by the vegetation habitat variables, food availability and human-related disturbance variables. A total of 61 species belonging to 33 families were recorded from the suburban area. 55 species belonging to 32 families were observed in nearby wildland habitat consisting of natural vegetation whereas only 26 species belonging to 18 families were observed in urban area. Results indicated that the suburban habitat had more complex bird community structure in terms of higher species richness, higher species diversity and higher evenness in comparison to urban and wildland habitat. Bird species richness and diversity varied across seasons. Maximum species richness and diversity was observed during spring season in all type of habitat. Most of the birds observed in urban areas were found to belong to either rare or irregular category on the basis of their abundance. The observed pattern of avian community structure is due to combined effect of both environmental and human related disturbance variables.

Bird communities and vegetation associations across a treeline ecotone in the Mealy Mountains, Labrador, which is an understudied part of the boreal forest

We examined the factors structuring bird communities across a complex subarctic treeline in the Mealy Mountains, Labrador, Canada. Using point counts of bird abundance in 2007 and 2008, we show that changes in vegetation driven by elevation are strongly correlated with avian community structure in this treeline ecotone system. Overall, avian diversity was higher in the forest compared with other habitat classes (krummholz, deciduous shrub, and alpine). There were strong correlations between avian diversity and vegetation richness, as well as structure, among and within habitat class in 2008. Numerous habitat types (subset of habitat class) were correlated with avian composition, although some species were clearly habitat generalists. Contrary to expectation, avian species composition was associated with physiognomy (vegetation structure) in alpine and deciduous shrub, and with either physiognomy or floristics (vegetation species composition) in krummholz and forest. Given the strong impact of elevation on vegetation and the demonstrated influence on bird communities, we note that for bird species whose near-southernmost populations are found in the Mealy Mountains, climate change is likely to have a strong negative effect if alpine tundra habitat is lost. Furthermore, forest bird species are likely to benefit from the increased tree cover as treeline moves poleward and upward.