Changes In Bird Species Composition Research Articles

Red clay roof and NDVI drive changes in bird species composition and functional evenness in housing areas of São Paulo megacity, Brazil


 
 
 Urbanization creates the most irreversible and human-dominated form of land use, often resulting in species losses and functional homogenization of bird communities. Here we investigate how housing areas in a Neotropical megacity may drive bird species occurrence and functional diversity in high densely habited areas. Using three local scales (radius of 50, 100, and 200 m), we tested how bird species richness, functional groups, and functional diversity indices may be affected by the normalized difference vegetation index (NDVI, a proxy for primary productivity) and the cover area (m2) of red clay roofs (RCR, likely urban nesting sites) in São Paulo megacity, Brazil. We recorded 40 bird species, mostly nesting on trees. Few and high abundant (native and exotic) birds may use roofs and other urban structures as nesting sites. The GLM models showed that functional evenness increased with synchronized increases of NDVI 200 m and RCR 200 m covers and decreased with increase of NDVI 50 m. Most of the bird indices were not affected by neither NDVI nor RCR at local scales. However, bird species composition and functional evenness were sensitive to NDVI and RCR. Our findings suggest that synchronized high values of NDVI (vegetation-linked resources) and RCR cover (likelihood of nesting) may improve the regularity of bird functional traits and ecosystem functions (e.g., frugivory and insectivory) in housing areas of a Neotropical megacity.
 
 

Similar composition of functional roles in Andean seed-dispersal networks, despite high species and interaction turnover.

The species composition of local communities varies in space, and its similarity generally decreases with increasing geographic distance between communities, a phenomenon known as distance decay of similarity. It is, however, not known how changes in local species composition affect ecological processes, that is, whether they lead to differences in the local composition of species' functional roles. We studied eight seed-dispersal networks along the South American Andes and compared them with regard to their species composition and their composition of functional roles. We tested (1) if changes in bird species composition lead to changes in the composition of bird functional roles, and (2) if the similarity in species composition and functional-role composition decreased with increasing geographic distance between the networks. We also used cluster analysis to (3) identify bird species with similar roles across all networks based on the similarity in the plants they consume, (i) considering only the species identity of the plants and (ii) considering the functional traits of the plants. Despite strong changes in species composition, the networks along the Andes showed similar composition of functional roles. (1) Changes in species composition generally did not lead to changes in the composition of functional roles. (2) Similarity in species composition, but not functional-role composition, decreased with increasing geographic distance between the networks. (3) The cluster analysis considering the functional traits of plants identified bird species with similar functional roles across all networks. The similarity in functional roles despite the high species turnover suggests that the ecological process ofseed dispersalis organized similarly along the Andes, with similar functional roles fulfilled locally by different sets of species. The high species turnover, relative to functional turnover, also indicates that a large number of bird species are needed to maintain the seed-dispersal process along the Andes.

Changes in bird species composition after a wind farm installation: A case study in South America

Facing the growing demand for renewable energy sources, the use of wind energy has been significantly increasing worldwide. Wind farms are known to present low environmental impact and their impact on bird fauna has been the most studied and discussed. In this study, we evaluated the composition of bird communities and changes in land use during three phases of wind farm development: pre-construction, construction and operation. Secondary data was obtained on bird communities, provided by the wildlife monitoring report submitted to the state environment agency of Rio Grande do Sul, Brazil. The total number of species recorded for all phases of wind farm construction was 163 species. One hundred species were present during all phases, and 20 were recorded during at least two phases, 32 species were exclusive to the pre-construction phase, four species were recorded only during the construction phase and seven recorded during the operation phase. The evaluation of bird community structure revealed that the pre-construction phase differed from the 4 years of operation, indicating that an impact on bird species' composition is evident, but more detailed and longer surveys are needed to confirm this trend. The bird community responded to landscape changes, mainly due to the reduction of native and exotic forest cover, in areas affected by wind farms installation and operation, in both, species' composition and environmental guilds. Analysis of secondary data allows us to evaluate which changes may have resulted from the implantation of the wind energy industry to the regional bird fauna, and our findings demonstrates tha the changes associated with the construction and operation of this wind farm have negatively affected the bird community.

Seed dispersal by changing frugivore assemblages: a mechanistic test of global change effects

In the face of global change it is important to understand how changes in species abundance and richness can affect ecosystem functions. Here we modelled seed dispersal by animals in a fragmented secondary forest of the Cantabrian Range (northwestern Iberian Peninsula), simulating the activity of six frugivorous bird species when dispersing three species of fleshy‐fruited trees. We calculated the density and richness of seeds deposited across a forested landscape, as well as the density of seeds arriving to open areas. We 1) study the complementarity of functional traits of each species with frugivore assemblages varying in species compositions (i.e. abundance and richness of bird assemblages), 2) identify those bird species whose functional roles are not redundant, and 3) explore the response of seed dispersal to random losses and to two non‐random bird loss scenarios (i.e. overhunting and fewer individuals from migrant species). We found that simulations with the avian composition observed in the field (i.e. with uneven abundances of six bird species) led to values of seed dispersal higher to those emerging from four bird species equally abundant. The selective removal of dominant bird species led to significant decays in seed dispersal, suggesting non‐redundant roles of abundant bird species. Seed dispersal decays were stronger under non‐random than random scenarios of bird loss. In terms of seed density, the functional decays also differed between the scenarios of overhunting and reduced arrival of migrant birds, notably beyond 50% changes in bird species composition. Our results illustrate the need to integrate species composition (controlling for bird abundance and richness) and their sensitivity to disturbances when predicting the impact of global change on ecosystem functions.

Local randomness, vegetation type and dispersal drive bird and mammal's diversity in a tropical South American region

How dispersal, environmental filters, and local extinctions affect species diversity depends on the species requirements for habitat, dispersal limitations, and abundance. Few studies have been able to properly separate these processes and to show how they affect the beta diversity patterns for multiple organisms. We investigated how the composition of birds and mammals changed along geographical and environmental gradients in an environmentally complex South American region. Using mantel tests and a null model approach we disentangled the effects of dispersal, environment, and stochastic processes in the species beta diversities. The similarity on species composition was negatively associated with the geographical distance separating areas for both groups. The changes in bird species composition likely resulted from their dispersal limitation over large geographical regions. In contrast, the composition of mammals in a given area was a partially random subset of the regional species pool, to some extent, filtered by the vegetation. Small communities tended to have more variable species composition, whereas dispersal limited birds showed a stronger distance‐decay pattern. Neither local randomness nor dispersal limitation prevented species from being filtered by the environment. Other groups are likely to show similar patterns depending on their dispersal abilities, environmental requirements and community size.

Changes in bird species composition on a remote and well-forested Wallacean Island, South-East Asia

In South-East Asia patterns of forest loss can predict the number of threatened birds. On the oceanic islands of Wallacea, small-scale agriculture, rather than commercial logging, is the main cause of forest loss and conversion, but few studies have directly examined their responses to land use. In 2001, I studied the birds of primary forest and anthropogenic gardens on the well-forested, and remote, Damar Island (198 km 2) in the Banda Sea. Furthermore, I examined broad changes to the islands bird fauna by comparing baseline bird lists obtained in the 19th century with 2001 data. The conversion of primary forest to garden resulted in substantial changes in avifaunal composition, and to the abundance of individual bird species, particularly to frugivorous and globally restricted-range species. Of 15 common birds, four were significantly more abundant in primary forest (blue-tailed imperial pigeon Ducula concinna, northern fantail Rhipidura rufiventris, golden whistler Pachycephala pectoralis and red-chested flowerpecker Dicaeum maugei) and one (scaly-breasted honeyeater Lichmera squamata) was more abundant in garden habitat. Incidental observations provided further evidence that many forest specialists (including the island endemic Damar flycatcher Ficedula henrici) rarely, if ever, used garden habitats notwithstanding its relative proximity. The number of resident birds recorded in 2001 (39) was similar to the 1890s (38), but six forest-dependent passerines were extirpated between samples. These losses are associated with the conversion of 25% of the primary forest to modified habitat since the 1890s, but given the sparse species and environmental change data available it is impossible to definitively pinpoint this as the only cause underlying the species losses. This study demonstrates that remote and relatively well-forested islands are not immune to the threatening processes impacting bird populations elsewhere in South-East Asia.

The effects of fire on grassland bird communities of Barberspan, North West Province, South Africa

Considering the frequent nature of fires and resultant drastic change in habitat following fire, research on the effects of fire on birds in the grasslands of South Africa is surprisingly scarce. For at least five months after burns we followed the changes in bird species composition, species richness and densities of two controlled burns and one accidental fire at the Barberspan Nature Reserve in grasslands that had not been burned or grazed in 10 years. Compared with the control areas, species richness and densities increased in the burned areas immediately following the burns, with more species and birds recruited to the burned areas than were lost. Immediate post-burn opportunists tended to be larger species, and the biomass increase mirrored the increases in species richness and densities in burned areas. Avian species richness, densities and biomass tended to return to the initial conditions after a number of months. Although the bird communities from two controlled-burns differed before the burns, they converged to a characteristic immediate post-burn composition. Five months after the burns however, the bird communities reflected a pre-burn composition. Indications were that birds in an area larger than that burned were affected. Mosaic burning, with shifting large and small patches, should be considered on a landscape scale.

Impacts of Livestock Grazing and Tree Clearing on Birds of Woodland and Riparian Habitats

We investigated the impact of pastoral management on birds in subtropical grassy eucalypt woodland in southeastern Queensland, Australia, where the patterns of land management have made it possible to disentangle the effects of livestock grazing from those of tree clearing. We recorded changes in bird species composition, density, and relative abundance across two woodland habitat types (riparian and nonriparian) and two levels of clearing (wooded and nonwooded) and three levels of livestock grazing (low, moderate, and high) replicated over space (1000 km(2)) and time (2001-2002). We predicted that species that depend on understory vegetation would be most negatively affected by livestock grazing. A Bayesian generalized linear model showed that the level of grazing had the greatest effect when trees were present. When trees were absent, the impact of grazing was overshadowed by the effects of a lack of trees. Over 65% of species responded to different levels of grazing, and the abundance of 42% of species varied markedly with habitat and grazing. The most common response to grazing was high species relative abundance under low levels of grazing (28% of species), species absence at high levels of grazing (20%), and an increase in abundance with increasing grazing (18%). Despite having similar bird assemblages, the effect of grazing was stronger in riparian habitat than in adjacent woodland habitat. Our results suggest that any level of commercial livestock grazing is detrimental to some woodland birds, particularly the understory-dependant species, as predicted. Nevertheless, provided trees are not cleared, a rich and abundant bird fauna can coexist with moderate levels of grazing. Habitats with high levels of grazing, on the other hand, resulted in a species-poor bird assemblage dominated by birds that are increasing in abundance nationally.

Effects of growth stage and tree species composition on breeding bird assemblages of plantation forests

Capsule Bird species assemblages are strongly dependent on growth stage and forest structure, but do not appear to be greatly affected by tree species composition. Aims To investigate changes in bird species composition of plantation forests in relation to crop tree species and forest growth stage. Methods We surveyed populations of birds in 44 plantation forests throughout Ireland in the summers of 2001 and 2002. Our study sites represented three combinations of tree species (pure Sitka Spruce Picea sitchensis, pure Ash Fraxinus exelsior, and Sitka Spruce/Ash mixed at inter-stand level) at five ages (4–8 years, 9–17 years, 23–29 years, 35–50 years and 50+ years). We used ordinations and indicator species analyses to explain the influence of growth stage and tree species composition on the bird assemblages of these forests. Results Bird species assemblage is dependent on growth stage. Changes in bird species composition over the commercial forest cycle are related to shrub layer and proximity to the forest edge. The bird assemblages of pre-canopy closure forests are typical of open habitats, some of the constituent bird species being of conservation concern within Ireland. As forests mature, these are replaced by commoner, more generalist species. We found no significant effect of tree species on bird species assemblage. Possible reasons for this include the relatively narrow range of tree species mixtures studied, and the paucity of forest specialist birds in Ireland. Conclusions Forest management for bird diversity in Ireland should promote the shrub layer in and around forest plantations, and ensure that new afforestation does not take place in areas with diverse communities of open-habitat birds. Opportunities for Irish forest plantations to provide habitat for bird forest specialists may be limited.

Influence of anthropogenic disturbance on bird communities in a tropical dry forest: role of vegetation structure

AbstractA study was carried out in Sariska Tiger Reserve in India to investigate the effects of anthropogenic disturbance caused by biomass extraction on the bird communities of tropical dry forests. The study was based on comparisons of the avifaunal community as well as vegetation structure between strictly protected (‘undisturbed’) and intensively used (‘disturbed’) sites that were demarcated a priori on the basis of disturbance indicators. There was no significant difference in the number of recorded species and bird abundance between disturbed and undisturbed sites. However, bird species diversity was significantly lower in disturbed sites. Bird species composition was found to differ significantly between disturbed and undisturbed sites and was associated with the measured disturbance indicators. Changes in bird species composition occurred because of seven of 26 locally abundant bird species (26.9%) responding significantly to the disturbance regime. All the affected bird species are primarily insectivorous. Bird species composition was significantly related to six vegetation structural variables, including two that were significantly altered by disturbance. Changes in vegetation structure accounted for all the changes in bird species composition caused by disturbance. However, vegetation structure had additional effects on bird species composition besides those caused simply by disturbance. Thus, our study indicates that forest use in the form of chronic biomass extraction can have significant effects upon bird diversity and species composition of tropical dry forest. There is a need to retain a proportion of natural ecosystems as inviolate if the full complement of biodiversity is to be conserved.

Spatio-temporal changes of a nature protection area in the agricultural landscape of Jaeren, South-West Norway

A nature protected area within agricultural landscapes is analysed based on studies of landscape metrics, vegetation and soil, as well as measurements of the water and matter balance. Landscape metrics analyses show the influences of agriculture in shaping the landscape over the past 65 years. Increased separation between intensively used agricultural land and low-productive wet fen areas is found. Both individual patches and the total area of arable land have increased in size. Changes restricted to the nature reserve are identified as to sedimentation and vegetation succession. Expansion of reed and Salix shrubs profits from nutrient fluxes from arable land and drainage canals. Plant compositions differ with regard to the complex nutrient balance which is affected by hydrologic conditions. Scenarios are drawn which indicate that extensive land use and landscape management neither prevent sedimentation processes nor reverse the successive development. We conclude that future changes in bird species composition and occurrence will have to be anticipated. Nature protection in agricultural landscapes based on structural stability must implement management measures. The authors suggest an approach including dynamic systems to support decisions within the frame of a sustainable development of changing landscapes.

DETECTING TRENDS IN SPECIES COMPOSITION

Species composition reflects a combination of environmental and historical events at a site; hence, changes in species composition can provide a sensitive measure of ecologically relevant changes in the environment. Here, we consider the analysis of species composition when multiple sites are followed through time. Analyses of temporal trends in species composition either summarize species composition into a few metrics (indices or axis scores) or analyze the similarity among sites. We develop and illustrate the similarity approach. Each pair of samples represents a pair of replicates, a pair from the same site at different times, a pair from different sites at the same time, or an unrelated pair. Differences among times can be estimated by comparing average temporal dissimilarity to average replicate dissimilarity. Temporal trends can be described by one of three statistics that measure progressive change, the correlation of temporal dissimilarity with the length of time between samples. These methods are illustrated using data on changes in a South Carolina zooplankton assemblage following disturbance, and changes in bird species composition on Skokholm Island, Wales. It is difficult to define and interpret temporal trends. Some definitions of interesting trends, like increasing divergence from another set of sample plots, place additional requirements on the sampling design. Including replicate samples or clustering sample plots and including “control” plots for comparison with sentinel sites would contribute to an understanding of changes in species composition.

Detecting Trends in Species Composition

Species composition reflects a combination of environmental and historical events at a site; hence, changes in species composition can provide a sensitive measure of ecologically relevant changes in the environment. Here, we consider the analysis of species composition when multiple sites are followed through time. Analyses of temporal trends in species composition either summarize species composition into a few metrics (indices or axis scores) or analyze the similarity among sites. We develop and illustrate the similarity approach. Each pair of samples represents a pair of replicates, a pair from the same site at different times, a pair from different sites at the same time, or an unrelated pair. Differences among times can be estimated by comparing average temporal dissimilarity to average replicate dissimilarity. Temporal trends can be described by one of three statistics that measure progressive change, the correlation of temporal dissimilarity with the length of time between samples. These methods are illustrated using data on changes in a South Carolina zooplankton assemblage following disturbance, and changes in bird species composition on Skokholm Island, Wales. It is difficult to define and interpret temporal trends. Some definitions of interesting trends, like increasing divergence from another set of sample plots, place additional requirements on the sampling design. Including replicate samples or clustering sample plots and including “control” plots for comparison with sentinel sites would contribute to an understanding of changes in species composition.

Inf luence of Within‐Plantation Heterogeneity and Surrounding Landscape Composition on Avian Communities in Hybrid Poplar Plantations

We conducted breeding bird surveys in Minnesota, Wisconsin, and South Dakota in 12 hybrid poplar plantations and surrounding landscapes from 1992 to 1994. Plantations varied in age, shape, composition of surrounding landscape, and internal vegetative heterogeneity. Numbers of breeding bird individuals and species in plantations were lower than in surrounding forest/shrub habitat, but higher than in row crops. Numbers of individuals observed within several bird groups based on migratory status and habitat preference also differed among plantations and surrounding land‐use types. Most differences were between numbers in plantations and row crops. Year‐to‐year changes in bird species composition in plantations were more likely in plantations between ages 2 and 4 years than in younger or older plantations. Correlative evidence from canonical correspondence analysis illustrated that plantation bird communities were related to habitat in surrounding landscapes, plantation age, size, latitude, and longitude. Additionally, more heterogeneous plantations had more species, individuals, and numbers of long‐distance migrants. Plantations will likely not support bird communities that are comparable to natural forests in either species composition or species diversity. A goal would be to position them in the landscape to minimize impacts on regional biodiversity. This could be accomplished by maintaining structural diversity of plantations by creating a broad range of successional stages (ages) throughout plantations within a region. Size and connectivity of existing forest fragments may be increased by plantations, but fragmentation of natural open areas should be avoided.

Avian community response to small-scale habitat disturbance in Maine

The effects of small clearcuts (1–8 ha) on avian communities in the forest of eastern Maine were studied using point counts during spring 1978 – 1981. Surveys were conducted in uncut (control) and clear-cut (treatment) plots in three stand types: conifer, hardwood, and mixed growth. We used a mark –recapture model and its associated jackknife species richness estimator [Formula: see text], as an indicator of avian community structure. Increases in estimated richness [Formula: see text] and Shannon–Weaver diversity (H′) were noted in the treated hardwood and mixed growth, but not in the conifer stands. Seventeen avian species increased in relative abundance, whereas two species declined. Stand treatment was associated with important changes in bird species composition. Increased habitat patchiness and the creation of forest edge are hypothesized as causes for the greater estimates of richness and diversity.

Songbird Responses to Commercial Clear-Cutting in Maine Spruce-Fir Forests

In commercially clear-cut and uncut spruce-fir (Picea-Abies) stands of northern Maine, the distribution of breeding songbirds was determined by habitat structure. We grouped 14 sampling areas into 5 seral stages. Stage I was characterized by dense slash and open ground, Stage II by dense raspberry stems and deciduous woody stems less than 2 m tall, Stage III by deciduous woody stems 2.1-4.5 m tall, Stage IV by deciduous woody stems taller than 4.5 m and trees with dbh 10-15 cm, and Stage V by a dense softwood overstory. Presence or absence of a softwood overstory was the most important habitat feature. Each seral stage was dominated by a characteristic group of breeding bird species. The data showed a predictable pattern in response of the breeding avifauna to changes in habitat structure following clear-cutting. J. WILDL. MANAGE. 43(3):602-609 There have been few studies on the effects of clear-cutting on birds in coniferous forest ecosystems, and none has dealt with this problem in spruce-fir forests in the northeastern U.S. Hagar (1960) in California and Franzreb (1975) in Arizona found marked changes in bird species composition following commercial clear-cutting in Douglas-fir (Pseudotsuga mensiesii) forests. In coniferous forests of Finland, Haapanen (1965) found that changes in the bird species using various stages of forest succession following timber harvest were due to changes in habitat structure of the forest stands. We examined the relationships between breeding songbirds and commercial clear-cutting in northern Maine. Our objective was to identify the habitat characteristics to which songbirds respond in clear-cut spruce-fir forests. The USDA Forest Service provided funding for this study through a cooperative agreement between the School of Forest Resources, University of Maine, Orono, and the Northeastern Forest Experiment Station. W. A. Wright, N. C. Famous, A. Kerr, M. S. Robson, L. A. Wright, and T. L. Stone helped with the bird and vegetation inventories. We thank M. W. Coulter, R. B. Owen, and R. M. Frank for their reviews of the manu-

An Ecological Analysis of Chaparral and Pine Forest Bird Communities on Santa Cruz Island and Mainland California

A comparative study of chaparral and pine forest bird communities on Santa Cruz Island and adjacent mainland areas was made during 1969—72. Five fewer species occurred in the island chaparral bird community and four fewer species in the island pine forest bird communities. Changes in bird species composition occurred most notably in the island pine forest, which is utilized by species commonly found in the chaparral. No significant changes in niche breadths were observed for the communities in general; however, a slight tendency for increased foraging height diversities on the island was observed. Average niche overlap values between species present on both the mainland and the island are greater on the island, mainly because of an increased vertical habitat overlap. By use of the observed mainland densities and competition coefficients composed of mainland overlap values, island densities were predicted for four bird species that show greater densities in the island chaparral community. Hence, competitive release occurs in the chaparral bird community. All communities studied are in a state of equilibrium, and the island communities are at least approaching a state of saturation equivalent to that of the mainland communities.