Bird Community Composition Research Articles

Influence of Landscape Composition on Avian Community Structure and Associated Mechanisms

Many recent studies have addressed the effects of patch size and isolation on bird communities in highly fragmented landscapes, but the importance of landscape composition in more forested landscapes remains poorly understood. The objectives of our study were (1) to determine the effects of two structurally and temporally distinct disturbance types (agriculture and silviculture) and extent of disturbance (percentage of disturbance within 1.0 km) on avian community structure within forested landscapes, and (2) to investigate underlying mechanisms responsible for associations between landscape composition and avian communities. Differences in microhabitat, microclimate, and nesting success among landscapes were examined as possible mechanisms. Breeding bird communities in central Pennsylvania (USA) were surveyed twice per year during 1997–1999 at 34 sites within contiguous mature forest, which represented a range of disturbance extent (4–59% nonforest cover within 1.0 km). Each site was in a forested landscape containing predominantly agricultural or silvicultural disturbances (n = 17 each). Our results indicate that type of disturbance within landscapes influenced bird community composition and relative abundance more than extent of disturbance. Compared to forests within landscapes disturbed by silviculture, forests within landscapes disturbed by agriculture, irrespective of the extent of disturbance, had fewer forest-associated species, long-distance migrants, forest-canopy and forest-understory-nesting species, and greater numbers of edge-associated species, including avian nest predators and Brown-headed Cowbirds (Molothrus ater). Fewer species and guilds were associated with the extent of disturbance within a landscape or interactions between disturbance type and extent. Abundances of edge-associated species, residents, and forest-canopy nesters increased with increasing amounts of disturbance within forested landscapes. Local variation in microhabitat and microclimate among landscapes did not explain observed differences in avian community structure. However, nesting success was greater and numbers of some avian and small mammalian nest predators were lower in stands within forested landscapes disturbed by silviculture than in forested landscapes disturbed by agriculture. Nesting success was not associated with the extent of a given disturbance type within landscapes. These results demonstrate that, even within forested landscapes, the types of disturbance can influence avian community structure and, thus, should be considered in conservation and forest management plans. In particular, agricultural disturbances within forested landscapes seemed to negatively affect bird communities in adjacent forests more than silvicultural disturbances. Both species richness and abundance of forest-associated species were greater on sites with higher levels of nesting success. Thus, differences in nesting success resulting from altered interactions between nest predators and nesting birds may be an important underlying mechanism of avian community structure and organization at the landscape scale.

INFLUENCE OF LANDSCAPE COMPOSITION ON AVIAN COMMUNITY STRUCTURE AND ASSOCIATED MECHANISMS

Many recent studies have addressed the effects of patch size and isolation on bird communities in highly fragmented landscapes, but the importance of landscape composition in more forested landscapes remains poorly understood. The objectives of our study were (1) to determine the effects of two structurally and temporally distinct disturbance types (agriculture and silviculture) and extent of disturbance (percentage of disturbance within 1.0 km) on avian community structure within forested landscapes, and (2) to investigate underlying mechanisms responsible for associations between landscape composition and avian communities. Differences in microhabitat, microclimate, and nesting success among landscapes were examined as possible mechanisms. Breeding bird communities in central Pennsylvania (USA) were surveyed twice per year during 1997–1999 at 34 sites within contiguous mature forest, which represented a range of disturbance extent (4–59% nonforest cover within 1.0 km). Each site was in a forested landscape containing predominantly agricultural or silvicultural disturbances (n = 17 each). Our results indicate that type of disturbance within landscapes influenced bird community composition and relative abundance more than extent of disturbance. Compared to forests within landscapes disturbed by silviculture, forests within landscapes disturbed by agriculture, irrespective of the extent of disturbance, had fewer forest-associated species, long-distance migrants, forest-canopy and forest-understory-nesting species, and greater numbers of edge-associated species, including avian nest predators and Brown-headed Cowbirds (Molothrus ater). Fewer species and guilds were associated with the extent of disturbance within a landscape or interactions between disturbance type and extent. Abundances of edge-associated species, residents, and forest-canopy nesters increased with increasing amounts of disturbance within forested landscapes. Local variation in microhabitat and microclimate among landscapes did not explain observed differences in avian community structure. However, nesting success was greater and numbers of some avian and small mammalian nest predators were lower in stands within forested landscapes disturbed by silviculture than in forested landscapes disturbed by agriculture. Nesting success was not associated with the extent of a given disturbance type within landscapes. These results demonstrate that, even within forested landscapes, the types of disturbance can influence avian community structure and, thus, should be considered in conservation and forest management plans. In particular, agricultural disturbances within forested landscapes seemed to negatively affect bird communities in adjacent forests more than silvicultural disturbances. Both species richness and abundance of forest-associated species were greater on sites with higher levels of nesting success. Thus, differences in nesting success resulting from altered interactions between nest predators and nesting birds may be an important underlying mechanism of avian community structure and organization at the landscape scale.

Are urban bird communities influenced by the bird diversity of adjacent landscapes?

Summary The species diversity of adjacent landscapes influences the conservation or restoration of several animal groups in urban areas, but the effect on birds is unclear. To address this question, we compared bird species richness (BSR) and community composition between periurban (area surrounding the town) and urban (suburban and centre areas) landscapes across three spatial scales. At a large biogeographical scale (temperate and boreal climatic zone), relationships between the BSR of urban areas and their surrounding landscapes were examined in a meta‐analysis of 18 published studies. In general, BSR was negatively correlated with latitude and urbanization. The BSR of suburban and centre landscapes correlated positively with the BSR of periurban landscapes. However, latitudinal effects were also involved, as BSR in urban and periurban landscapes declined as town latitude increased. Similarity indices were low (50%) between periurban and centre bird communities. At a regional scale, we assessed winter bird data from several towns within three regions of temperate and boreal countries (western France, northern Finland and eastern Canada). The type of periurban landscape, number of inhabitants and town diameter did not affect BSR. BSR was similar between the cities of a given biogeographical area. Bird communities were more similar between similar habitat types of different cities than between different habitats of the same city. At a local scale, we tested the influence of proximity to the periurban landscape on BSR in parks of western French towns of different size. Neither BSR nor community similarity changed in relation to the distance of the park from the periurban landscape. Guild composition according to diet and feeding habitat did not vary between urban and periurban locations at regional or local scales. We conclude that, at regional and local scales, urban bird communities are independent of the bird diversity of adjacent landscapes, and that local features are more important than surrounding landscapes in determining BSR. Whatever the biodiversity quality of the periurban landscape, site‐specific actions such as shrub and tree planting, water restoration and increasing vegetation diversity can change bird diversity in towns and improve the quality of human–wildlife contacts.

Influence of remnant and landscape attributes on Australian woodland bird communities

This study investigated relationships between the composition of bird communities and remnant and landscape attributes including area, shape, vegetation type and position in the landscape. Vegetation type was the strongest determinant of bird communities. The bird community of river red gum forests was most different from that of white cypress pine woodlands, with the bird communities of other vegetation types intermediate between these two extremes. Honeyeaters and hollow-nesting birds were associated with river red gum forests, whereas small insectivores were associated with white cypress pine woodlands. Bird communities also varied significantly with remnant size. Small insectivores were more likely to be found in remnants larger than 200 ha, whereas noisy miners and grey butcherbirds were more likely to be found in remnants smaller than 100 ha. Vegetation type, remnant area, absence of noisy miners and presence of small insectivores are interrelated. It is likely that the aggressive noisy miner, rather than remnant size per se, determines the presence or absence of small insectivores in remnants. Remnant attributes appeared to be more important than landscape attributes in determining the composition of bird communities, although the widespread occurrence of noisy miners may inhibit the benefits that landscape vegetation might provide. As long as an aggressive edge specialist dominates small remnants and there is a shortage of quality, core patches that might benefit from connectivity, we consider that a focus on landscape connections is a dangerous diversion for efforts directed towards biodiversity conservation. Large, high-quality patches must be established and protected for the conservation of declining birds.

A CANONICAL CORRESPONDENCE ANALYSIS OF THE EFFECTS OF THEEXXON VALDEZOIL SPILL ON MARINE BIRDS

To assess how the Exxon Valdez oil spill affected habitat occupancy by communities of marine-oriented birds in Prince William Sound, Alaska, we conducted a canonical correspondence analysis (CCA) using data collected between 1989 and 1996 in 10 bays that had been exposed to different levels of oiling. CCA creates a multivariate space defined by a combination of environmental variables and measures of the abundances of the bird species present in the bays. The locations of individual sites (site scores) in this multivariate space indicate how bird-community composition at the sites varies in relation to the combination of environmental variables, while the locations of individual bird species (species scores) indicate the mean values of the response curves (abundance variations) of species on the CCA axes. Relationships among the site scores of sites exposed to different levels of oiling may therefore be used to evaluate the effects of the spill on the bird communities occupying these sites, and the relationship of a species score to the site scores indicates the conditions under which the species is, on average, most abundant. In surveys conducted the summer after the oil spill, the site scores for unoiled or lightly oiled (“unoiled”) bays occupied a region of the CCA space that was largely separate from that occupied by the moderately or heavily oiled (“oiled”) bays, indicating consistent differences in bird-community composition. Although the structure of the CCA ordination and site locations in that space varied among seasons and years, the separation of the unoiled and oiled site scores in the CCA space continued. Rather than indicating continuing spill effects, however, the separation of site scores was probably related to environmental differences among the bays and chance differences among bays in the reassembly of bird communities following the spill. Consideration of the locations of species scores in the CCA space clarified the patterns of spill impacts and subsequent recovery. The increase in the number of bird species present in early summer surveys between 1989 and 1990 was associated with the occupancy of previously oiled bays by species that were absent in 1989 or that previous analyses had shown to be initially impacted by the spill. Species scores for birds for which the previous analyses showed continuing spill impacts in early summer 1990 were associated most closely with the site scores of the unoiled bays. The species scores of several species that occurred too infrequently to be evaluated in the previous studies were associated with the site scores of the unoiled bays in 1989, suggesting initial spill impacts. In subsequent years, these species scores were associated with the site scores of the previously oiled bays, suggesting reoccupancy of those bays. Patterns for surveys conducted in midsummer generally were similar to those in early summer. Surveys conducted in midsummer 1996 suggested continuing recovery in the use of initially oiled habitats by birds, including some species that did not show clear evidence of recovery in 1991. Overall, these analyses showed that the Exxon Valdez oil spill had clear initial impacts on bird species and communities in the study bays in Prince William Sound, but they also provided clear evidence of increasing occupancy of previously oiled sites. Multivariate analyses such as CCA can provide valuable insights into the complex responses of environments and biological communities to large-scale contamination events when precontamination data are lacking, especially when the analyses are repeated over time and the changing relationships of both species and site scores in the multivariate space are considered.

Riparian bird communities in relation to land management practices in floodplain woodlands of south-eastern Australia

Bird communities are declining in south-eastern Australia and riparian woodlands are critical habitats for birds in this agricultural region. We investigated how terrestrial bird communities varied with different land management practices (levels of grazing by domestic livestock and extent of clearing) and with habitat quality on the floodplains of the Murrumbidgee and Murray Rivers. Bird community composition in ungrazed and lightly grazed sites was significantly different to that in more heavily grazed sites, and these differences were related to tree and shrub cover, as well as tree species diversity and abundance of standing dead trees. Grazing appeared to have an effect on bird communities separate from that caused by clearing. Indicator species were identified for the effects of grazing and clearing. Grazing by livestock has had negative impacts on riparian birds through degradation of habitat quality. A combination of lower stocking rates, strategic placement of off-river watering points for stock, and the introduction of rotational grazing practices may be used to restore riparian habitat quality. The grazing-sensitive species we identified could be used as indicator species for the success of rehabilitation efforts.

The effect of 50 years of landscape change on species richness and community composition

AbstractWe analysed a 50‐year dataset of avian species observations to determine how richness and community composition varied over a period of landscape‐scale environmental change. Our study area, northern lower Michigan, has experienced substantial land‐use and land‐cover change over time. Like much of the northern Midwest, it has shifted from a largely unpopulated, post‐logging shrubland to a moderately populated closed‐canopy forest. Such changes are generally expected to influence overall richness and community composition. We found that regional richness per year remained virtually unchanged over the study period. Year‐to‐year variation in species number was surprisingly low. Richness totals included vastly different species groups as the composition of the regional bird community changed substantially over time. Changes in the types of species present appear to reflect deterministic changes in habitat. The number of grassland and open‐habitat species decreased, for example, while species associated with older forests and urban habitats increased. Our results suggest that habitat changes at the landscape scale do not necessarily lead to changes in the number of species a region can support. Such changes, however, do appear to influence the types of species that will occupy a region, and can lead to substantial changes in community composition.

Breeding and Migrating Birds in an Amazonian Savanna

Seasonal occurrence, breeding and migration records are presented for about 150 species of birds, monitored during a four years survey in an Amazonian savanna near Alter do Chão, Pará state, Brazil, by means of mist netting and observations along transects and on random walks. About half of the recorded species were Passeriformes. The local avifauna was mostly comprised of residents, with major breeding activities during the dry season, August through February. Thirteen non-resident species were classified as migrants which is considered a rather small fraction. Calculations of the total number of species expected to occur at the study site are presented. The composition of this savanna bird community is discussed under aspects of seasonality and migrational activity. The data are compared with records from other cerrado habitats in Amazonia and elsewhere, especially in Central Brazil. Resumo Registros de ocorrência sazonal, reprodução e migração são apresentados para cerca de 150 espécies de aves, monitoradas durante quatro anos de levantamentos em uma savana Amazônica perto de Alter do Chão, Estado do Pará, Brasil, através de redes ornitológicas, observações ao longo de transectos e caminhadas ao acaso. Perto da metade das espécies registradas foram passeriformes. A avifauna local foi constituída principalmente de espécies residentes, com o pico de atividades reprodutivas durante a estação seca, ou seja 80% das espécies reproduzindo de Agosto até Fevereiro. Este padrão se repetiu em 1988 e 1989. Juvenis foram capturados durante todo o ano com picos durante a estação chuvosa. Treze espécies não residentes foram consideradas migrantes os quais são uma pequena fração da comunidade. Estimativas do número total esperado de espécies ocorrendo na área de estudo são apresentados. As capturas com redes ornitológicas em 4 ha resultaram em 41 espécies e para 13 ha, 64 espécies. Quando a área amostrada foi duplicada para 24 ha, o número de espécies aumentou em somente 4 e correspondeu à metade do total registrado para a área. O número assintótico estimado para 13 ha foi de 82 espécies o qual foi similar ao número estimado para 24 ha (80 espécies). A composição desta comunidade de aves de savana é discutida sob os aspectos de sasonalidade e atividades migratórias. Os resultados são comparados com registros de outros habitats de cerrado na Amazônia e outros locais especialmente no Brasil central.

Effects of forest fragmentation on birds of the cerrado region, Brazil

Bird surveys were conducted through observations and mist-netting in six forest fragments in the cerrado region of central Brazil, to evaluate the effects of fragmentation on bird species richness and community composition. Smaller forest fragments had fewer species than larger fragments. The proportion of species in most foraging guilds did not change with forest size, except for that of granivores, which decreased as fragment size increased. The proportion of forest-dependent species increased significantly with increasing fragment size while that of semi-dependent species significantly decreased. Forest-dependent endemic birds, however, were not area sensitive, but appeared to be partially dependent on the flooded forests of the region. Conservation policies for the region should conserve both large and small forest fragments urgently, and flooded forests especially.

Vegetation and bird community dynamics in fragmented coppice forests

Richness and composition of plant and bird communities were used to evaluate the importance of seven within‐forest factors on biodiversity in fragmented coppice forests in south‐western France. Plants and birds were sampled on the same 98 plots. Plant abundance–dominance was measured on 400 m 2 plots. Birds were sampled using a 50‐m fixed radius point‐count method in the early and late periods of the breeding season. The selected factors were: years since logging (YSL), retention of standards (STANDARD), ownership (OWNER), distance to the nearest edge (EDGE), tree richness (TREE), density of vegetation in low (ST 2 ) and high (ST 16 ) strata. Paired comparisons of richness were carried out between YSL classes, according to other variables. The respective influence of each variable was evaluated using adapted CCA (canonical correspondence analysis) on plant and bird composition. Plant richness varied strongly between YSL classes, was independent of STANDARD, increased with TREE and was higher in collective owned forests. Bird richness seemed to be independent of YSL and was higher in low YSL plots with standards. Bird and plant richness was not correlated. Plant community composition was mainly explained by YSL/ST 16 on the first axis and by OWNER on the second axis. STANDARD and OWNER explained bird community composition. OWNER must be considered as a synthetic variable. This could be useful in adapting forestry practices for a better management of biodiversity, taking into account the very different taxonomic groups involved.

Seasonal Fluctuations of Birds, Fruits, and Flowers in a Subtropical Forest of Argentina

AbstractI quantified monthly variation in species composition and captures of birds in a premontane forest of northwestern Argentina. Seasonal patterns of frugivore-insectivores and nectarivores were compared with fruit and flower abundances, respectively. The composition of the entire bird community fluctuated seasonally; frugivore-insectivores showed a peak in captures during the wet season, insectivores peaked at the end of the dry season, and nectarivores peaked during the dry season. At a local scale (∼50 ha), captures of frugivore-insectivores were not correlated with number of plant species with ripe fruits for any vegetation stratum considered, but were correlated with a fruit phenology index that considers crop size. At a plot scale (∼7.5 ha), only understory flower abundance and captures of nectarivores were correlated, but only in the plot where both were more abundant. At a net-site scale (50 m2), captures of the Rufous-bellied Thrush (Turdus rufiventris) were correlated with understory fruit abundance, but only in the plot where fruits were more abundant. These results suggest that seasonal fluctuations in birds may be driven to some extent by their food resources. Premontane forest provides habitat for many migrants and also presumably acts as a source of birds that emigrate to disturbed areas. Although premontane forests should be a conservation priority for the region, they are poorly protected and suffering high deforestation.

Projecting the bird community response resulting from the adoption of shelterbelt agroforestry practices in Eastern Nebraska

Evolving agricultural policies have influenced management practices within agroecosystems, impacting available habitats for many species of wildlife. Enhancing wildlife habitat has become an explicit objective of existing agricultural policy. Thus, there is renewed focus on field borders and the use of shelterbelt agroforestry systems to achieve conservation goals in the Midwest. Two Representative Farms – a 283-ha dryland and 510-ha irrigated farm were created in Saunders County, Nebraska. The Habitat Analysis and Modeling System (HAMS) was used to describe the composition and spatial pattern of the existing farms and surrounding landscape, as well as for the landscapes surrounding selected Breeding Bird Survey (BBS) routes. Simulated land use changes resulting from the implementation of two shelterbelt scenarios, Agricultural and Wildlife, were incorporated on each Representative Farm and surrounding landscape. Landscape variables which influence breeding bird species richness and community composition as determined from BBS routes were measured on simulated farm landscapes. A more heterogeneous landscape results from implementing either scenario. The percent total woods was a significant determinant of bird species richness on the BBS routes and was important in influencing bird communities at the farm- and landscape-level. Other landscape metrics which influenced the bird community composition on BBS routes were woody edge percentages and edge density values. Policies promoting shelterbelts create edge habitats which ultimately favor birds within the Forest-edge/generalist guild while bird species in need of conservation such as grassland-field species would potentially be negatively affected.

Factors affecting bird communities in fragments ofsecondary pine forests in the north-western Mediterranean basin

Abstract We assessed the influence of size, extent of isolation and vegetation structure of secondary forest fragments on the richness and species composition of breeding bird communities in a sample of pine forest fragments surrounded by an agricultural matrix in the north-western Mediterranean basin. Fragment size was the main predictor of bird’s occurrence, since it accounted for 70 % of the model variation. Isolation was also a valuable predictor of species occurrence, especially for forest specialists. Finally, subarboreal vegetation such as holm oak and a well-developed tree layer of large pines favoured forest species occurrence. Therefore, in spite of the long history of human impact, forest birds in Mediterranean mosaics are sensitive to both habitat loss and isolation of remnant patches in a similar manner to the patterns found in other temperate fragmented landscapes where human impact is more recent.

SEASONAL FLUCTUATIONS OF BIRDS, FRUITS, AND FLOWERS IN A SUBTROPICAL FOREST OF ARGENTINA1

Abstract I quantified monthly variation in species composition and captures of birds in a premontane forest of northwestern Argentina. Seasonal patterns of frugivore-insectivores and nectarivores were compared with fruit and flower abundances, respectively. The composition of the entire bird community fluctuated seasonally; frugivore-insectivores showed a peak in captures during the wet season, insectivores peaked at the end of the dry season, and nectarivores peaked during the dry season. At a local scale (∼50 ha), captures of frugivore-insectivores were not correlated with number of plant species with ripe fruits for any vegetation stratum considered, but were correlated with a fruit phenology index that considers crop size. At a plot scale (∼7.5 ha), only understory flower abundance and captures of nectarivores were correlated, but only in the plot where both were more abundant. At a net-site scale (50 m2), captures of the Rufous-bellied Thrush (Turdus rufiventris) were correlated with understory fruit...

Bird community composition patterns in urban parks of Madrid: The role of age, size and isolation

This study intends to assess the influence of fragment age, size and isolation (from the regional species pool) on bird community composition patterns in urban parks in Madrid, and the role of local and regional factors on community structure. Park age was a good indicator of habitat complexity. Park age and area accounted for 62% of the variability in species richness, but two measures of isolation from the regional species pool were not included as significant factors. Species composition in urban parks showed a high degree of nestedness, which was associated with park age and area, but not with two measures of isolation from the regional species pool. The degree of nestedness increased with park age; the distribution of species varying from nested in old and mature parks to random in young parks. The incidence (% of species occurrence in parks) in young parks was correlated with regional densities, whereas in mature and old parks the incidence was correlated with local densities. In this urban landscape, species composition appears to be regulated by local factors (particularly in mature and old parks), such that species accumulate in an orderly (not random) fashion in relation to park age and area. Regional influences seem to be more pronounced only in young parks, which are mainly colonized by species from the regional species pool.

Bird community as an indicator of biodiversity: results from quantitative surveys in Brazil.

This short review presents the results obtained in several localities of Brazil on the composition of forest bird communities. Data were collected since the late 80's, after we introduced a new methodology of quantitative survey, based on acoustic identification and unlimited-radius point census. Although these data are still scattered, they show uniquely precise and coherently comparative patterns of composition of forest bird communities. Our methodology has the advantage of being absolutely non-disturbing, highly efficient in the field and immediately processed. Results confirm that the structure of a bird community is a good indicator of biodiversity, particularly useful where biodiversity is high. Many of these data are available only in unpublished dissertations and abstracts of congress communications, or are being analysed. A cooperative program is needed to promote new surveys and publish their results, as a contribution for measuring and monitoring biodiversity, especially in complex endangered habitats.

Managing the Abundance and Diversity of Breeding Bird Populations through Manipulation of Deer Populations

Abstract: Deer densities in forests of eastern North America are thought to have significant effects on the abundance and diversity of forest birds through the role deer play in structuring forest understories. We tested the ability of deer to affect forest bird populations by monitoring the density and diversity of vegetation and birds for 9 years at eight 4‐ha sites in northern Virginia, four of which were fenced to exclude deer. Both the density and diversity of understory woody plants increased following deer exclosure. The numerical response of the shrubs to deer exclosure was significantly predicted by the soil quality (ratio of organic carbon to nitrogen) at the sites. Bird populations as a whole increased following exclosure of deer, particularly for ground and intermediate canopy species. The diversity of birds did not increase significantly following exclosure of deer, however, primarily because of replacement of species as understory vegetation proceeded through successional processes. Changes in understory vegetation accounted for most of the variability seen in the abundance and diversity of bird populations. Populations of deer in protected areas are capable of causing significant shifts in the composition and abundance of bird communities. These shifts can be reversed by increasing the density and diversity of understory vegetation, which can be brought about by reducing deer density.

LANDSCAPE-SCALE DISTURBANCES AND CHANGES IN BIRD COMMUNITIES OF BOREAL MIXED-WOOD FORESTS

Bird community response to both landscape-scale and local (forest types) changes in forest cover was studied in three boreal mixed-wood forest landscapes modified by different types of disturbances: (1) a pre-industrial landscape where human settlement, agriculture, and logging activities date back to the early 1930s, (2) an industrial timber managed forest, and (3) a forest dominated by natural disturbances. Birds were sampled at 459 sampling stations distributed among the three landscapes. Local habitat and landscape characteristics of the context surrounding each sampling station (500-m and 1-km radius) were also computed. Bird communities were influenced by landscape-scale changes in forest cover. The higher proportion of early-successional habitats in both human-disturbed landscapes resulted in significantly higher abundance of early-successional bird species and generalists. The mean number of mature forest bird species was significantly lower in the industrial and pre-industrial landscapes than in the natural landscape. Landscape-scale conversion of mature forests from mixed-wood to deciduous cover in human-disturbed landscapes was the main cause of changes in mature forest bird communities. In these landscapes, the abundance of species associated with mixed and coniferous forest cover was lower, whereas species that preferred a deciduous cover were more abundant. Variation in bird community composition determined by the landscape context was as important as local habitat conditions, suggesting that predictions on the regional impact of forest management on songbirds with models solely based on local scale factors could be misleading. Patterns of bird species composition were related to several landscape composition variables (proportions of forest types), but not to configuration variables (e.g., interior habitat, amount of edge). Overall, our results indicated that the large-scale conversion of the southern portion of the boreal forest from a mixed to a deciduous cover may be one of the most important threats to the integrity of bird communities in these forest mosaics. Negative effects of changes in bird communities could be attenuated if current forestry practices are modified toward maintaining forest types (deciduous, mixed-wood, and coniferous) at levels similar to those observed under natural disturbances.

Edge Effects on the Understory Bird Community in a Logged Forest in Uganda

Abstract: Understanding how the fauna of logged tropical rainforests responds to fragmentation and the creation of edges is vital to ensure conservation of biodiversity. We studied the composition of the understory bird community from the edge of a 15‐ha clearing toward the interior of the forest in a part of Budongo Forest Reserve, Uganda, that was selectively logged about 45 years ago. Mist netting was conducted along five transects from the edge and 500 m into the interior. The total number of individuals captured did not change with distance from the edge, but there was a significant increase in the number of species. We sampled fewer, but more common species near the edge, whereas the interior of the forest had more, and less common species. Guild composition also changed with distance from the edge. Frugivore‐insectivores and nectarivores were most common close to the edge. Among insectivores, ground foragers, bark‐gleaners, and leaf‐gleaners were most common in the interior of the forest, whereas sallying insectivores favored the edge. Graminivores were unaffected by the edge. Analysis of common species showed that Ispidina picta, Andropadus curvirostris, A. latirostris, Camaroptera brachyura, Terpsiphone rufiventer, and Nectarinia olivacea were associated with the edge, but no species showed significant avoidance of the edge. This finding may be explained by the generally low sample sizes of interior species. Our results show that even bird communities in logged forests respond to edges. Estimates of edge effects suggested that changes in bird densities may have occurred several hundred meters from the edge. In conclusion, logged forests provide habitat for bird species avoiding forest edges, and this should be considered in the management of such forests for conservation.

Long-term trends in avifaunal recolonisation of rehabilitated bauxite mines in the jarrah forest of south-western Australia

Alcoa of Australia Limited rehabilitates areas in the jarrah forest of south-western Australia following bauxite mining. One of the aims of the company's rehabilitation programme is to re-establish the faunal communities which existed prior to mining. In the summers of 1981, 1987 and 1993, company biologists conducted bird surveys as part of a case study to determine the extent of avifaunal recolonisation in representative mined areas. Analysis of monitoring data collected during the three surveys of the same areas showed considerable variation in the avifaunal communities of three rehabilitated sites. Numbers of bird species and bird diversity in a site seeded with dense understorey continued to increase, and by 1993 all avifaunal community parameters measured in this site were equal to or greater than those recorded in healthy unmined forest. Bird species numbers increased in a site given fresh topsoil but not seeded between 1981 and 1987; however, all parameters showed little further change by 1993. The oldest site, which was not seeded or given fresh topsoil, showed the greatest degree of change. In 1981, it supported only one bird species, but by 1993 all bird community parameters were similar to those recorded in the site which received fresh topsoil but no seed. Species composition of all rehabilitated sites' avifauna also changed. The similarity of bird community composition increased over time. By 1993, the healthy forest communities were more similar to those of some rehabilitated sites than to those of forest degraded by dieback disease. The study demonstrated that development of the vegetation community is a key factor controlling the composition of bird communities in rehabilitated mine sites. Recommendations are given to further promote avifaunal recolonisation following mining.