Birds In Patches Research Articles

Bird community structure in native forest fragments and Acacia mangium plantations in Borneo

ABSTRACT In Southeast Asia, some plantation developers have retained patches of native forest within plantations to promote wildlife diversity, but relatively few studies have examined the effectiveness of such efforts. To provide more information on the interaction between native forest and plantation, we conducted surveys of birds in patches of logged native forest and surrounding groves of exotic plantations in Borneo. We asked the following questions: Does plantation age influence the bird community in adjacent native forest fragments? Are bird communities in the plantations influenced by the presence of small fragments of native forest? Are bird communities in more intensively managed plantations different compared to less intensively managed plantation? Do bird distributions across habitat types vary by functional trait? Our study was conducted in a 500,000 ha multi-use landscape in Sarawak, Malaysia. We identified 15 native forest fragments within exotic plantation, and these were partitioned into ...

Bird Communities in Amazonian White‐Sand Vegetation Patches: Effects of Landscape Configuration and Biogeographic Context

AbstractVegetation growing on white‐sand soils is patchily distributed across the Amazon and is characterized by scrublands or open vegetation types (white‐sand campinas) and by forests (white‐sand forests) surrounded by contrasting habitat types. We studied birds in patches of white‐sand campinas in contrasting landscapes in four regions located in distinct biogeographic units delimited by major rivers. Our aim was to investigate the contribution of landscape configuration and biogeographic context to patterns of species diversity and distribution. Aracá and Viruá landscapes (on opposite sides of Rio Branco) are composed by large and continuous patches of white‐sand campinas, while Jaú, Novo Airão and Uatumã landscapes (on opposite sides of Rio Negro) are composed by small patches of white‐sand campinas isolated by continuous terra firme forests. Birds were sampled using mist‐nets and qualitative censuses, and were classified as white‐sand vegetation specialists or non‐specialists. Bird species diversity was significantly different among studied regions, and composition was significantly different for both, specialists and non‐specialists birds. Local variability in species diversity and composition was best explained by white‐sand campina area, patch proximity, and distance to major rivers. We conclude that landscape configuration and biogeographical context influence patterns of bird diversity, abundance, and composition in Amazonian white‐sand campinas.

The effect of local and landscape-level characteristics on the abundance of forest birds in early-successional habitats during the post-fledging season in western Massachusetts.

Many species of mature forest-nesting birds (“forest birds”) undergo a pronounced shift in habitat use during the post-fledging period and move from their forest nesting sites into areas of early-successional vegetation. Mortality is high during this period, thus understanding the resource requirements of post-fledging birds has implications for conservation. Efforts to identify predictors of abundance of forest birds in patches of early-successional habitats have so far been equivocal, yet these previous studies have primarily focused on contiguously forested landscapes and the potential for landscape-scale influences in more fragmented and modified landscapes is largely unknown. Landscape composition can have a strong influence on the abundance and productivity of forest birds during the nesting period, and could therefore affect the number of forest birds in the landscape available to colonize early-successional habitats during the post-fledging period. Therefore, the inclusion of landscape characteristics should increase the explanatory power of models of forest bird abundance in early-successional habitat patches during the post-fledging period. We examined forest bird abundance and body condition in relation to landscape and habitat characteristics of 15 early-successional sites during the post-fledging season in Massachusetts. The abundance of forest birds was influenced by within-patch habitat characteristics, however the explanatory power of these models was significantly increased by the inclusion of landscape fragmentation and the abundance of forest birds in adjacent forest during the nesting period for some species and age groups. Our findings show that including factors beyond the patch scale can explain additional variation in the abundance of forest birds in early-successional habitats during the post-fledging period. We conclude that landscape composition should be considered when siting early-successional habitat to maximize its benefit to forest birds during the post-fledging period, and should also be included in future investigations of post-fledging habitat use by forest birds.

Effects of forest disturbance and habitat loss on avian communities in a Neotropical biodiversity hotspot

Regenerating forests are increasingly ubiquitous in tropical landscapes. They hold great conservation potential and there is demand for assessments of their biodiversity value. Forest disturbance and forest loss often occur together, yet few studies attempt to disentangle their separate effects on biological communities. In the Ecuadorian Chocó, a biodiversity hotspot, we sampled understory birds in patches with increasing levels of disturbance (old-growth, selectively-logged, and secondary forests) within contiguous forest and in fragments. Species richness increased with disturbance but decreased with habitat loss, with a 75% reduction in endemic and threatened species in fragments compared to contiguous forest. This reduction in richness was most pronounced in secondary forest fragments, suggesting that disturbance and habitat loss interact synergistically to maximally reduce avian biodiversity. Species composition was strongly affected by habitat loss and, to a lesser extent, disturbance, with forest fragments and secondary forests presenting distinct communities dominated by generalists with medium-to-low sensitivity to anthropogenic disturbance and reduced proportions of endemics and endangered species. Capture rates also decreased (non-significantly) with habitat loss, and the relative abundance of dietary guilds varied in response to both habitat loss and disturbance. Our study shows that regenerating patches surrounded by contiguous forest can sustain high biodiversity levels and, when past habitat disturbance is mild, present similar communities to old-growth forests. In contrast, forest loss caused reductions in richness (especially in more disturbed patches), profound changes in community composition, and loss of species of conservation concern. These results underscore the importance of considering landscape context when evaluating the conservation value of disturbed forests.

Plant and bird diversity in natural forests and in native and exotic plantations in NW Portugal

Forest ecosystems have been subjected to continuous dynamics between deforestation and forestation. Assessing the effects of these processes on biodiversity could be essential for conservation planning. We analyzed patterns of species richness, diversity and evenness of plants and birds in patches of natural forest of Quercus spp. and in stands of native Pinus pinaster and exotic Eucalyptus globulus in NW Portugal. We analyzed data of forest and non-forest species separately, at the intra-patch, patch and inter-patch scales. Forest plant richness, diversity and evenness were higher in oak forest than in pine and eucalypt plantations. In total, 52 species of forest plants were observed in oak forest, 33 in pine plantation and 28 in eucalypt plantation. Some forest species, such as Euphorbia dulcis, Omphalodes nitida and Eryngium juresianum, were exclusively or mostly observed in oak forest. Forest bird richness and diversity were higher in both oak and pine forests than in eucalypt forest; evenness did not differ among forests. In total, 16 species of forest birds were observed in oak forest, 18 in pine forest and 11 in eucalypt forest. Species such as Certhia brachydactyla, Sitta europaea and Dendrocopos major were common in oak and/or pine patches but were absent from eucalypt stands. Species-area relationships of forest plants and forest birds in oak patches had consistently a higher slope, at both the intra and inter-patch scales, than species-area relationships of forest species in plantations and non-forest species in oak forest. These findings demonstrate the importance of oak forest for the conservation of forest species diversity, pointing the need to conserve large areas of oak forest due to the apparent vulnerability of forest species to area loss. Additionally, diversity patterns in pine forest were intermediate between oak forest and eucalypt forest, suggesting that forest species patterns may be affected by forest naturalness.

Bird populations in native forest patches in south-eastern Australia: the roles of patch width, matrix type (age) and matrix use

We surveyed birds in patches of native eucalypt forest and in surrounding exotic matrix (Radiata pine forests) in south-eastern Australia. Our objectives were: (1) to examine the influence of the width of native forest patches and the age of surrounding pine forests on bird occurrence in patches of native forest; and (2) to verify the relationship between the use of the surrounding pine matrix and bird species response to variation in width of patches of native forests. A total of 32 study sites (boundaries between eucalypt and pine forests) were surveyed. Birds were counted by the area search method within 0.5-ha quadrats. Data were analysed using generalised linear models. Wide patches of eucalypt forest supported higher species richness and greater numbers of birds, such as foliage searchers and nectarivores, than narrow patches. Matrix age also influenced the occurrence of some species in native patches. The abundance of species in wide and narrow patches of native forest was related to their use of the matrix. This was true for native forests surrounded by old but not by young pine forests. We suggest that management in wood production landscapes take into account both characteristics of native patches and the surrounding matrix. Negative impacts of fragmentation in managed landscapes might be reduced by promoting matrix types that are suitable for bird species.

Birds in patches of old-growth ash forest, in a matrix of younger forest

Birds were studied at 57 sites in Mountain Ash forests in the Central Highlands of Victoria, Australia in spring and summer 1995/96. The sites represented 41 patches of old-growth forest (up to 390 ha in size) in a matrix of regrowth mostly from severe fires in 1939 (57 years previously), with multiple sites in the four largest patches of old-growth and eight sites in 1939 regrowth. Relative bird abundance was assessed by an area-search technique. Generalized linear modelling was used to develop predictive models by regressing abundance of groups of bird species against patch size, isolation and some basic habitat and context variables. Total bird abundance (of all species combined) tended to be higher in old-growth patches than in 1939 regrowth, but not significantly. There was no trend in total abundance with patch size or isolation. Fruit-eating birds tended to be commonest in small patches. Bark-foragers and uncommon birds favoured large patches, though the latter were most common in 1939 regrowth. More variation was explained by habitat and context variables such as aspect, altitude and forest structure. Unevenaged forest structure was often associated with small patches. It was concluded that old-growth forest patches can have similar values per hectare for forest birds whether they are large or small. The regrowth forest matrix appears to protect small patches from factors which reduce densities of forest birds in small forest patches in farmland. The data support the current policy of retaining all old-growth ash forest patches. A range of factors should be considered in selecting regrowth stands of various sizes to regrow as old forest of the future, including their intrinsic potential to develop particular habitats and produce a mix of forest stuctures in the landscape.

Land use, habitat change and the conservation of birds in fragmented rural environments: a landscape perspective from the Northern Plains, Victoria, Australia

Studies of the effects of habitat fragmentation on birds have mainly been carried out at the patch scale, by censusing birds in patches of different size, shape or composition. Here, we use data collected by observers for the Atlas of Australian Birds from 10' latitude/longitude grid cells (landscapes), each 277 km2 in size, to examine the effects of land use and habitat change at the landscape scale in the Northern Plains region of Victoria, Australia. Land birds were tallied for 63 such landscapes and species were classed as "woodland" or "other" species. Attributes measured for each landscape represented natural environmental variation, tree cover and the intensity of human settlement. The Northern Plains has experienced profound environmental change over the last century of agricultural settlement and tree cover now occupies only 6.2% of the region, mostly as large riverine forests. Eighty per cent of landscapes have less than 10% tree cover. Woodland birds showed substantial variation in richness between landscapes and, after accounting for sampling effort, species richness was best predicted by total tree cover and measures of environmental variation (e.g., number of streams). "Other" birds were more evenly distributed between landscapes. Species richness was best predicted by the environmental gradient in rainfall and temperature, although this accounted for only a small amount of variance after correcting for sampling effort. The predictive model for woodland birds indicates that this group is sensitive to habitat change, and implies a substantial loss of species in landscapes that have been almost entirely cleared of woodland habitat. The logarithmic nature of the relationship means that the rate of change in species richness is greatest during the final stages of habitat depletion. With median tree cover of 3.7% for landscapes in the region, this relationship supports the contention that a major decline in woodland birds is underway and that species are being lost from whole landscapes across the region. Attributes associated with landscapes of high conservation value for birds include: extensive overall tree cover, large blocks of woodland habitat, and stream systems with associated habitat connectivity. In this region, these attributes are more likely to occur in areas with broad-acre agriculture rather than intensive irrigation. The analysis suggests that at least 10% tree cover is a minimum goal for an infrastructure of natural vegetation in rural landscapes to prevent serious decline and loss in the woodland avifauna.