Changes In Composition Of Bird Communities Research Articles

Habitat changes explain shifts in bird community composition in abandoned military training areas: Lessons for conservation

Military training areas are important biodiversity refuges and may serve as viable components of regional conservation networks, mainly due to the blocking of ecological succession by the disturbance regime creating a heterogeneous open habitat mosaic hosting many threatened species. However, European armies have undergone downsizing over the past decades and numerous military training areas have been abandoned. The assessment of the consequences of this abandonment for biodiversity would show us whether these abandoned areas still provide conservation benefits. For this purpose, we carried out bird surveys in 30 abandoned military training areas in Czechia. The surveys were performed in two periods (2009 and 2020–2021) to track small-scale changes in land cover and bird abundance after the areas were abandoned in the 1990s. We tested (i) whether changes in bird abundance were related to land cover changes and (ii) whether the observed bird species’ responses to the land cover changes can be explained by species-specific characteristics. Multivariate spatial analyses uncovered significant shifts in land cover composition towards a higher representation of dense shrub, forest and built-up areas at the expense of open areas represented by grassland and sparse shrub. These land cover changes explained a small but significant part of bird abundance variation across the areas. Correspondingly, species benefiting from these land cover changes were associated with dense scrub or forest, such as the Common Chiffchaff, Willow Warbler, or Eurasian Blackcap, whereas species suffering from these changes were associated with grassland, such as the European Stonechat and Eurasian Skylark. Phylogenetically informed interspecific analysis aiming to explain changes in bird abundance between periods confirmed that population declines were linked to open habitat preference, while population increases were linked to the preference for dense shrub and forest. In addition, we found that protected species increased their abundance, most likely due to the existence of conservation management that kept their habitats available. These patterns indicate that military training areas transform toward later successional stages after their abandonment with corresponding changes in bird community composition. However, these changes may not necessarily be negative provided that species of conservation concern enjoy the support of conservation management.

Semi-natural habitats on organic strawberry farms and in surrounding landscapes promote bird biodiversity and pest control potential

Agricultural intensification and expansion have degraded biodiversity in agroecosystems, jeopardizing the ecosystem services provided by wildlife. Birds can act as particularly important purveyors of ecosystem services to farmers by consuming arthropod pests. Some bird species, however, may sometimes act as pests themselves by consuming crops. Further, on-farm management practices (e.g., crop diversity, vegetative structure) and the complexity of the surrounding landscape can shift the balance of bird-mediated ecosystem services and disservices through changes in bird community composition. Here, we explored how organic strawberry farms in California could be managed to bolster bird biodiversity and shift community composition from strawberry-consuming to pest-eating species. Using multi-species N-mixture models we found that semi-natural habitat at the landscape (1000 m) and farm (50 m) scales were positively associated with mean abundance of all birds, with varying effects on different species. In particular, we found that the mean local abundance of species that consume Lygus spp. (a major pest), but not strawberry-consuming species, increased with semi-natural habitat at the farm scale. Nest density in developed areas within farms also increased with greater semi-natural habitat in the landscape, while nest density in semi-natural habitat within farms decreased with increasing semi-natural habitat in the landscape. Further, nest density of Lygus spp. eating birds increased with increasing local semi-natural habitat. These results suggest that increasing semi-natural habitat at the landscape and local scales can bolster bird abundance across farms, while pest control can be promoted locally by conserving or restoring semi-natural vegetation at the farm scale.

Fire ecology for the 21st century: Conserving biodiversity in the age of megafire

Fire ecology for the 21st century: Conserving biodiversity in the age of megafire

Effects of changes in bird community composition and species abundance on plant reproduction, through pollination and seed dispersal

The consequences of global bird declines on ecosystem function are gaining increasing attention. Here we consider the effects of changes in bird community composition and species abundance on reproduction for two endemic plant species in New Zealand. Birds service a relatively high proportion of the New Zealand flora as both pollinators and seed dispersers, and bird losses have been extensive during the 700 years since human colonization. We compare fruit set and seed removal for plants in reserves free of introduced predators, where seven endemic flower and fruit visiting bird species were present and relatively abundant, with plants outside these reserves where endemic bird species were absent or at lower abundance. The study plants, Dysoxylum spectabile and Pittosporum crassifolium, have both flowers and fruit visited by birds. Both species are also dioecious (a characteristic that has not been commonly associated with bird‐pollinated plants) and despite having mixed pollination systems, bird visits are essential for successful seed production. Outside introduced predator‐free reserves, the winter‐flowering D. spectabile was still visited by endemic pollinators and maintained pollination levels, despite a 59% decrease in endemic bird abundance. However, reduced endemic bird abundance was associated with a halving of pollination levels in P. crassifolium, which flowers in spring, as do other native and introduced flowering plants attractive to birds. The effect of altered bird species composition and abundance on seed dispersal was associated with a 74% reduction in seed dispersal for P. crassifolium. Additionally, undispersed seeds of P. crassifolium had lower germination, and higher pre‐dispersal seed predation, compared with dispersed seeds. We stress three important aspects of these results: (1) for some plant species, the same bird species perform both pollination and seed dispersal, (2) dispersal reduces pre‐dispersal seed predation, so that dispersal failure secondarily increases losses to seed predators, and (3) the effects of mutualism loss are not even across all species. Our results highlight that introduced species do not adequately replace endemic mutualists, which may be a particular problem for plant species with both bird‐visited flowers and fruit.

Wintering bird communities are tracking climate change faster than breeding communities.

Global climate change is driving species' distributions towards the poles and mountain tops during both non-breeding and breeding seasons, leading to changes in the composition of natural communities. However, the degree of season differences in climate-driven community shifts has not been thoroughly investigated at large spatial scales. We compared the rates of change in the community composition during both winter (non-breeding season) and summer (breeding) and their relation to temperature changes. Based on continental-scale data from Europe and North America, we examined changes in bird community composition using the community temperature index (CTI) approach and compared the changes with observed regional temperature changes during 1980-2016. CTI increased faster in winter than in summer. This seasonal discrepancy is probably because individuals are less site-faithful in winter, and can more readily shift their wintering sites in response to weather in comparison to the breeding season. Regional long-term changes in community composition were positively associated with regional temperature changes during both seasons, but the pattern was only significant during summer due to high annual variability in winter communities. Annual changes in community composition were positively associated with the annual temperature changes during both seasons. Our results were broadly consistent across continents, suggesting some climate-driven restructuring in both European and North American avian communities. Because community composition has changed much faster during the winter than during the breeding season, it is important to increase our knowledge about climate-driven impacts during the less-studied non-breeding season.

城市化鸟类群落变化及其与城市植被的关系

持续而快速的城市化进程正在助长全球生物多样性的丧失，其中鸟类是城市生态系统的重要环节和城市生物多样性保护的重点目标，同时也是研究的热点内容。从城市环境变化压力下，鸟类群落组成与结构、空间分布和繁殖营巢方式的改变分析，重点介绍了支持城市地区鸟类多样性的植物环境因素与影响机制的最新研究成果。结果表明：1）城市中的植被和绿色空间为城市鸟类提供生存空间和食物资源，是城市鸟类最主要的栖息地。2）保留原生乡土植物和大型树木的地区能支持更丰富的鸟类物种。3）植被的结构和盖度对鸟类群落有显著影响。林冠覆盖率增加，复杂的垂直空间和多样的植物种类的组合产生各种不同类型的植物空间和栖息地类型，吸引不同的鸟类物种，相应地也会导致更丰富的鸟类群落。总之，保持和加强城市中植物环境良好和稳定是保护城市生物多样性的有效手段。据此，提出城市环境与鸟类群落关系研究的未来发展方向，指出了其在鸟类多样性保护和城市可持续发展等领域的应用前景。;There are more than half of the world's human population living in cities. The vast amount of predicted rapid urbanization in the coming years consuming habitats and reducing the possibilities for wildlife to thrive in cities, and is contributing to the loss of global biodiversity. Among them, birds are the most important part of urban ecosystem and a key target for urban biodiversity protection. Besides, it is also a research hotspot. The last 20 years of urban bird ecology research have experienced exponential growth and now enables literature analyses and reviews. Here, we try to roundup these present findings on urban bird communities research from all over the world, overviewing patterns and variation processes on urban bird community, especially the changes in composition and structure, spatial distribution, living habits and the way of breeding and nesting under this continuous and rapid urbanization. To further assess the importance of and contributions provided by urban green space and vegetation to the urban bird community, exploring its affecting mechanisms that support bird diversity in urban areas, we reviewed the published literature for such studies. The results showed that: 1) Provision of greenery can ameliorate the hostility of the urban environment for wildlife, as well as provide suitable living space and food resources for urban birds. Green spaces provide the most important habitats for urban birds. 2) Not all forms of greening benefit bird communities to the same extent. Compared to those areas that do not pay much attention to native plant protection, areas that retain natural or semi-natural cover and large trees can support richer bird species. 3) Structure and coverage of vegetation have significant impacts on bird communities. The increasing canopy coverage, complex vertical structures and many kinds of plant species can produce various types of plant spaces and heterogenetic habitats. The increased plant spaces and habitats can cause changes in bird community composition, a correspondingly increase in species richness and diversity. In conclusion, maintaining and strengthening the healthy and stable of vegetation communities in cities is an effective strategy to conserve urban biodiversity. Collectively, protecting existing and planting new greenery has great potential to restraint urban biodiversity loss. Based on these, we propose the future research development direction of the relationship between the urban environment and bird communities. Further, the application prospects of this research in bird diversity protection to provide a more resilient, stable, and sustainable urban system are also pointed out.

Long-term response of forest bird communities to retention forestry in northern temperate coniferous forests

Retention forestry aims to maintain structural and functional continuity in managed stands. While short-term benefits to forest dwellers are well documented, few studies have followed patterns over decades to assess whether benefits continue. Initiated in 1992, the Date Creek Research Forest in northwest BC includes four replicates of four retention levels: 0% (clearcut), 40%, 70% and 100% (unharvested control). These ~20-hectare stands, with retention designed to mimic typical insect and wind disturbance, are now entering the canopy closure seral stage. We followed breeding bird community dynamics over 25 years (pre-harvest and 24 years post-harvest). Given relatively consistent landscape conditions over time, we focused on stand-level changes in bird community composition and species abundance. Community similarity to controls decreased as retention decreased; communities changed over time, with those in clearcuts changing most. Patterns in species abundance varied with habitat preference. Conifer-forest species declined immediately after harvest, with some responding linearly to retention level while others responded similarly to 40%, 70% and 100% treatments; Pacific Slope Flycatcher, Pacific Wren and Brown Creeper remained significantly less abundant in some treatments by year 24. Open-habitat and generalist species increased most in clearcut and somewhat in 40% retention stands, with generalists taking advantage of the increased heterogeneity immediately and open-habitat species colonizing by year 10; some of these species, particularly shrub specialists, remained at high abundance in harvested stands in year 24. Mixed-forest species reached their highest abundance at 40% retention in year 2 and 10, and dropped to control levels by year 24. Although conifer-forest, open-habitat and generalist species treated retention stands as intermediate between clearcuts and controls, mixed-forest species perceived them as a different, preferred habitat for the first decade. We conclude first that most forest birds do not discriminate between 70% retention stands and unharvested forest, confirming strategies in the region to maintain biodiversity in landscape corridors, second that aggregated 40% patch retention partially or fully mitigates impacts for conifer-forest birds, and provides new habitat for mixed-forest and open-habitat species, and third that bird communities are still changing after 24 years as these stands enter canopy closure.

Changes in forest cover result in a shift in bird community composition

AbstractDetermining the extent of land‐use change that can be tolerated by wildlife communities is crucial for effective conservation management. Recent landscape‐scale studies have found increasing evidence for critical threshold levels of forest cover, after which the existing communities of plants and animals are negatively impacted. This is particularly true when plantation forests replace native vegetation. We used large datasets (Irish Bird Atlas and Forest Inventory) and a novel method, Latent Dirichlet Allocation, to model changes in bird community composition along the existing forest cover gradient in Ireland and evaluated the degree of spatial overlap between birds of conservation concern and areas of recent afforestation. We found that as we approach 35% forest cover in the landscape one community of birds replaces another as the dominant community. The highest levels of recent afforestation overlapped with areas of high numbers of birds of conservation concern. This means that habitat change is occurring in the areas with highest bird diversity. This finding has policy implications for the design of land‐use policies, such as those on afforestation and forest expansion. It can be used to ensure plantation forests are planted in the right place to minimise impact on biodiversity values; that is, practitioners need to consider the level of forest already present in an area as well as the level of biodiversity in the area when selecting areas for afforestation.

Changes in bird community composition in the Czech Republic from 1982 to 2004: increasing biotic homogenization, impacts of warming climate, but no trend in species richness

Recent major environmental changes could lead to homogenization in the composition of plant and animal communities, with generalist species replacing more specialized species, as well as to the increased domination of species adapted to warmer climatic conditions. Using common bird monitoring data, we have tested whether these patterns can be observed in the long-term changes in the structure and species richness of bird communities in the Czech Republic. We focused on a comparison of two time periods (1982–1990 and 1991–2004) that differ in land use (high agricultural intensity in the former, and a drop in agricultural intensity accompanied by forest expansion in the latter). We found that bird communities became less specialized and that this decline in specialization did not change after 1990. In contrast, taxonomic homogenization increased during the first time period but declined at the beginning of the second one. Moreover, the community composition developed towards a dominance of species breeding in warmer climates, and this change coincided with an increase in spring temperatures. Therefore, it would appear that both functional and taxonomic homogenization took place in the 1980s but the latter did not continue in subsequent decades. Species richness of local bird communities did not show any trend over time. We suggest that climate warming might be an important driving force of changes in the bird community composition in the Czech Republic, but the role of land-use changes is less clear, although it is probable that habitat specialists probably did not benefit from lower intensity of agricultural activities and increased forest cover.

Rapid changes in bird community composition at multiple temporal and spatial scales in response to recent climate change

Although climate change is acknowledged to affect population dynamics and species distribution, details of how community composition is affected are still lacking. We investigate whether ongoing changes in bird community composition can be explained by contemporary changes in summer temperatures, using four independent long‐term bird census schemes from Sweden (up to 57 yr); two at the national scale and two at local scales. The change in bird community composition was represented by a community temperature index (CTI) that reflects the balance in abundance between low‐ and high‐temperature dwelling species. In all schemes, CTI tracked patterns of temperature increase, stability or decrease remarkably well, with a lag period of 1–3 yr. This response was similar at both the national and local scale. However, the communities did not respond fast enough to cope with temperature increase, suggesting that community composition lags behind changes in temperature. The change in CTI was caused mainly by changes in species’ relative abundances, and less so by changes in species composition. We conclude that ongoing changes in bird community structure are driven to a large extent by contemporary changes in climate and that CTI can be used as a simple indicator for how bird communities respond.

Breeding bird assemblages in riparian galleries of the Guadiana River basin (Portugal): the effect of spatial structure and habitat variables

AbstractHabitat structure is a major determinant of bird community composition and a link between riparian vegetation and bird communities in riparian zones, suggesting that changes in bird community composition can be predicted from changes in habitats. Our study aimed to identify the relationships between the structure of breeding bird communities and environmental drivers, using fine‐resolution habitat measurements. We examined two bird assemblages (Passerines, P; and Aquatic/Riparian species, AR) and their spatial structure and relationships to environmental river variables in riparian galleries in southern Portugal. The study was conducted on the ca. 230 km of riparian corridors located in the flooded area of the Alqueva reservoir, before closure of the dam. We used data from 134 10‐min point counts. Using variation partitioning, we determined the independent and joint effects of river edge, river bed, and spatial variables on our selected bird assemblages. The variation in bird assemblages captured was 27.5% for P and 55.3% for AR. The explanatory variables that were highlighted as important predictors for both bird groups were variables that reflected the complexity of the riparian gallery vegetation: rivers with high vegetation cover of riparian species, and riverbeds and riversides dominated by rock and scarce emergent rooted vegetation. Most of the explained variation was related to environmental variables: river‐edge, river‐bed, and their joint effect. Riparian areas can be considered a specific habitat and the variables analyzed are habitat descriptors at a fine scale, so that we believe that the species–environment relationships revealed in this study could be good indicators of the wealth of riparian ecosystems in Mediterranean rivers.

Bird community composition in an actively managed savanna reserve, importance of vegetation structure and vegetation composition

The mosaic of trees, shrubs and open grassland in mesic African savannas is highly dynamic and strongly influenced by mammal herbivory and fire. We investigated the bird fauna in four different savanna habitats to help assess the impacts of vegetation change on this component of faunal diversity. Birds were censused, plant species were identified and vegetation structure was measured in four different vegetation types (Acacia nilotica woodland, Acacia nigrescens woodland, broadleaf thicket and open grassland) in the Hluhluwe-Umfolozi Park in northern KwaZulu Natal, South Africa. Multivariate ordination analyses were used to determine the relative importance of vegetation structure and floristic composition in defining bird assemblages. The bird communities of the grasslands, the acacia woodlands, and the broadleaf woodlands were clearly separated on the first axis of the detrended canonical correspondence analysis (DCCA). Canopy cover and foliage height diversity (FHD) were strongly correlated with the first axis of DCCA, possibly reflecting a secondary successional series from grassland to woodland, known as bush encroachment. Floristic composition (based on presence–absence data only) seemed to be less important for bird community composition than vegetation structure. The results indicate that changes in vegetation structure, caused by bush encroachment, could cause concomitant changes in bird community composition.

Subfossil avian deposits from Poukawa, Hawkes Bay, and the first record ofOxyura australis(Blue-billed Duck) from New Zealand

Abstract An assemblage of subfossil avian remains deposited over a period of 7 ,000 years at Poukawa, Hawkes Bay, is examined. The abundance of many of the larger bird taxa (Apteryx, Cygnus, Notomis, Circus, Strigops) appears to have declined over the whole period, and they were all rare by 1,000 years ago. The considerable changes in bird community composition at Poukawa during the last 1,000 years, including the extinction of many species, probably resulted from forest modification caused by fires lit by Polynesian man. Differences in the occurrence of various skeletal elements of the birds are apparent, and possible reasons for this are discussed. The first New Zealand record of Oxyura australis Gould, 1836 (Bluebilled Duck) is reported.

Habitat Structure, Patchiness, and Avian Communities in North American Steppe Vegetation: A Multivariate Analysis

We investigate the relationships between vegetational structure, spatial heterogeneity, avian community structure, and the ecological responses of the breeding bird populations in the structurally simple steppe vegetation of North America. We examined the effect of variation in several measures of both horizontal and vertical patchiness in vegetation distribution on bird distribution and abundance, then integrated these measures into a smaller subset of variables using Principal Component Analysis (PCA). We interpreted the new PCA variables as reflective of proximate niche parameters to which bird species responded. Out of 550 structure/bird abundance bivariate correlations, 18.5% achieved a significant level of at least P <.05. Virtually all individual species responses to vegetation habitat measurements were straightforward: all “typical tallgrass prairie” birds attained highest abundances on plots with highest percent coverage of grass, “typical shrubsteppe” birds attained their highest abundances on plots with the highest values of shrub coverage, and so on. In the PCA of vegetational features, the first axis (which accounted for 41.0% of the total variation) represented in horizontal structure and heterogeneity of vegetation, with high positive factor loadings for 9 of 10 horizontal measures. The second component (22.4%) represented increasing vertical heterogeneity, with significant correlations for five of five vertical measures. The third component(10.7%) reflected variation in the density and coverage of low forbs. The segregation of horizontal and vertical measures on orthogonal axes indicates that variation in horizontal vegetation patchiness is largely independent of variation in vertical patchiness in these steppe systems. The abundances of all typically tallgrass prairie bird species were negatively correlated with increasing horizontal heterogeneity and partially correlated with increasing vertical heterogeneity. Several shrubsteppe bird species were also positively associated with increasing vertical heterogeneity, but unlike tallgrass birds their abundances were also positively associated with increasing horizontal patchiness. Shortgrass prairie birds were generally negatively correlated with vertical patchiness. Only bird species associated with montane meadows varied significantly with changes in the third principal component, forb abundance. At the community level, species diversity increased as vertical heterogeneity increased but appeared to vary independently of horizontal patchiness. Temporal variation in overall vegetation structure was not closely mirrored by correlated changes in bird community composition at the shortgrass prairie site for which yearly data were available. Analysis of species' niche overlaps along the synthetic vegetation axes defined by PCA revealed a significant lack of niche complementarity; species with high overlap on one axis were quite likely (P < .001) to have high overlap on a second, independent axis. Analysis of nich metrics across communities indicated that while average niche breadths of co—occurring species were independent of a sample's position on any multidimensional axis, average nich overlap increased at the nonmontane grassland sites. Tests of current theories of "diffuse competition" vs. “niche breadth compensation for low alpha;diversity” were inconclusive. We suggest that the conventional sorts of data collected to test the hypotheses, are inappropriate. Our results suggest that individual bird species responded independently to the environmental gradients we derived, and that higher species interactions were not necessary (and in some cases statistically improbable) to explain the patterns we observed. These results are consistent with our contention that even though such biotic interactions may be taking place, they are unlikely to be detected in our systems because (1) environmental variation obscures relationships between local populations, (2) populations, are not resource limited or equilibrial during large portions of their history, and (3) individuals are not "fine tuning" their responses to local habitat variation.