Effects of anthropogenic land use on forest birds and butterflies in Subic Bay, Philippines

Despite the loss of 83% of native forests in the Philippines, little is known on the effects of this massive habitat loss and degradation on its forest biotas. This is a cause for concern because of the threat posed to the country’s large number of endemic taxa. To investigate the impacts of anthropogenic disturbance, forest birds and butterflies were surveyed in closed and open canopy forests, as well as suburban, rural and urban areas within the Subic Bay Watershed Reserve and Olongapo City in western Luzon. Measures of forest species richness and population densities for both taxa were similar in the two forest types, but showed different patterns in the other habitats. Indirect gradient analysis showed that forest bird species were positively correlated with vegetation variables (i.e., canopy cover, tree density, height to inversion and ground cover), while forest butterflies were not strongly correlated to any of the measured habitat variables. Community composition of birds in forests was distinct from those in modified habitats, while butterfly communities were more similar. A simulation showed that canopy cover of 60% or higher was required by 24 of the 26 bird species that were sensitive to canopy loss. Endemicity and nesting strata were the significant predictors of vulnerability to habitat disturbance for birds, while endemicity and larval hostplant specificity were significant for butterflies. Both taxa were negatively affected by anthropogenic disturbance but may respond to different components in the habitat (i.e., structure and resources), and thus cannot be used as surrogates of each other. Conservation of forests with contiguous canopy cover should be prioritized, and more ecological research is needed to improve the knowledge on the effects of disturbance on Philippine biodiversity.     

Comparing bird community responses to forest fragmentation in two lowland Central American reserves

Habitat loss and fragmentation reduce diversity of tropical bird communities, but the predictability of how communities in fragments disintegrate over time remains unclear. We compared bird community changes of two lowland forest reserves, La Selva Biological Station (LSBS), Costa Rica and Barro Colorado Island (BCI), Panama, both approximately the same size (1500 ha) and at similar latitude (9-10 N) in Central America. Both reserves are losing bird species despite LSBS’s connection to an existing large park (incomplete isolation) and BCI’s favorable location within a largely forested landscape. We examined characteristics of guilds and species lost from the sites to determine whether patterns were similar, and thus predictable. Some of the same guilds declined at both reserves, particularly insectivores and ground/understory nesters. At LSBS mixed-species flock participants, forest species, and burrow-nesters also declined or became extirpated disproportionately. At BCI edge species became extirpated. Body mass was a poor predictor of species and guild loss at both sites, except for carnivores at La Selva. Thus, fragmentation appears to influence some guilds more than others, but which species decline or disappear in tropical forest fragments is also influenced by site-specific factors, mostly yet to be determined. We need to understand such idiosyncratic effects of fragmentation better, rather than rely on one-size-fits-all management plans to conserve bird communities in tropical forest fragments.     

Patch size and isolation effects on epiphytic and epiphyllous bryophytes in the fragmented Brazilian Atlantic forest

An inventory of the understory forest epiphyte and epiphyllous bryophyte floras was carried out in eight Atlantic rain forest fragments. The fragments were between 7 and 500 ha in size and belonged to two areas (lowland and submontane) of the state of Pernambuco, northeastern Brazil. The aim of this study was to investigate the effect of habitat fragmentation and changes in the natural landscape on community structure (composition, richness, diversity, and abundance). Although the influence of altitude was noted in this study by increasing richness, diversity, and abundance, it was clear that in some fragments the influence of fragment size and isolation can be more important than this positive environmental factor. Fragment size and isolation affect both communities but the last one seems to be a stronger threatening factor for the epiphylls. The least isolated and the largest fragments housed the richest floras - especially in relation to the epiphylls - and had the greatest proportion of shade species. Habitat fragmentation negatively affected epiphytic and epiphyllous bryophytes and increased the representation of species with larger niches (generalists) while decreasing the representation of species with smaller niches (typically found in shady or in sunny areas). The results suggests that the critical fragment size necessary for bryophyte preservation must be correlated with insularity levels; for epiphytes, however, it is likely that low levels of isolation cannot compensate borderline effects as with the epiphyllous bryophytes.     

High rates of forest clearance and fragmentation pre- and post-National Park establishment: The case of a Jamaican montane rainforest

The principal defense of tropical forests has been to designate them as protected areas, but few of these protected areas have been studied to determine their effectiveness at preventing forest clearance within their boundaries. We used remote sensing techniques to quantify three fundamental forest cover change processes: forest clearance, re-growth and fragmentation over a 19-year time period, in a National Park of Jamaica. Results show that forest clearance occurred at similar high levels prior and subsequent to the establishment of the area as a National Park in 1993: 1.50% yr⁻¹ (1983–1992) and 1.42% yr⁻¹ (1992–2002), respectively. Fragmentation continued post-establishment, and manifested itself in an increasing number of smaller more vulnerable fragments; the number of fragments increased by 60%, and the mean fragment size decreased by 40%. Core areas decreased with ensuing increases in edge lengths, and fragments became more isolated from one another. After designation as a National Park however, increased forest re-growth occurred, resulting in a 63% decline in the net deforestation rate from 0.80% yr⁻¹ (1983–1992) to 0.26% yr⁻¹ (1992–2002). Image classifications gave accuracies of 90–97% (Kappa 0.80–0.93). Although the decrease in net deforestation may indicate some level of success of this National Park, forest clearance and fragmentation, leading to species shifts and biodiversity loss were still present at pre-National Park levels. We then examined the preponderance of successful protected areas, and found that success may be an artifact of the most widely used method of assessment, which compares deforestation rates inside versus outside protected areas.     

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 km²) 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.     

Habitat structure and proximity to forest edge affect the abundance and distribution of forest-dependent birds in tropical coastal forests of southeastern Madagascar

Despite the fact that Madagascar is classified a biological `hotspot' due to having both high levels of species endemism and high forest loss, there has been no published research on how Madagascan bird species respond to the creation of a forest edge or to degradation of their habitat. In this study, we examined how forest bird communities and different foraging guilds were affected by patch habitat quality and landscape context (forest core, forest edge and matrix habitat) in the threatened littoral forests of coastal southeastern Madagascar. We quantified habitat use and community composition of birds by conducting 20 point counts in each landscape contextual element in October and November 2002. We found that littoral forest core habitats had significantly (p<0.01) more bird species than forest edge and matrix habitats. Thirty-one (68%) forest dependent species were found to be edge-sensitive. Forest edge sites had fewer species, and a higher representation of common species than forest interior sites. Twenty-nine species were found in the matrix habitat, and the majority of matrix-tolerant forest species had their greatest abundance within littoral forest edge habitats. Guild composition also changed with landscape context. Unlike other tropical studies with which we are familiar, we found that frugivorous species were edge-sensitive while sallying insectivores were edge-preferring. The majority of canopy insectivores (n=15, 88%), including all six endemic vanga species, were edge-sensitive. When habitat quality was assessed, the distributions of nine edge-sensitive species were significantly (p<0.01) affected by changes in habitat complexity and vegetation vertical structure in core or edge point counts. Therefore, we believe that changes in vegetation structure at the edge of littoral forest remnants may be a key indicator of mechanisms involved in edge sensitivity of forest dependent species in these forests. Our findings indicate that habitat fragmentation and degradation affect Madagascan bird communities and that these processes threaten many species. With continued deforestation and habitat degradation in Madagascar, we predict the further decline of many bird species.     

High sensitivity of montane bird communities to habitat disturbance in Peninsular Malaysia

Over the past few decades, the montane forests of Peninsula Malaysia have been severely impacted by the cultivation of exotic crops and urban sprawl. To guide conservation initiatives, montane bird communities were studied to determine their response along a disturbance gradient with the aim of identifying key factors influencing their distribution. Habitat types surveyed included primary and secondary montane forests, a tea plantation, rural, and urban areas in Cameron Highlands and Fraser’s Hill. Response variables included species richness and density quantified via point counts and mistnet surveys. Explanatory variables measured were related to vegetation structure, food abundance and land-use cover. Estimated ‘true’ species richness was higher for pristine and minimally disturbed sites, lower in tea plantation and lowest in heavily developed town centres. Nonmetric multidimensional scaling revealed that both vegetation structure (e.g. canopy density) and land-use cover (e.g. proportion of forest cover) influence species distribution; certain invasive lowland birds were tolerant of extreme development and native montane birds, in general, endured only slight habitat disturbances. A simulation indicated that montane forest dependant species richness started to decline when more than 20% of the canopy cover was lost. Less than a third of the species richness remained when more than 40% of the canopy cover was cleared. The logistic regression model suggested that sensitive species nested lower, were restricted to montane habitats and foraged in mid or high canopy. The dominance of lowland invasives in highly developed urban sites reveals that homogenisation of bird communities can occur even at higher altitudes (>1400 m a.s.l.). The results indicated that native montane birds communities are sensitive to habitat loss and degradation. Thus, any development in the highlands must proceed with minimal disturbance to montane forests, of which, keeping the canopy cover intact should be a crucial consideration.     

Effects of habitat disturbance on mixed species bird flocks in a tropical sub-montane rainforest

Despite their vulnerability to forest disturbances in the Neotropics, the consequences of forest perturbation on mixed species flocks are poorly understood in the threatened Southeast Asian rainforests. We examined the effects of local-scale habitat disturbance on mixed species flocks along an escalating gradient of anthropogenic modification (i.e., forest interior, forest edge, and urban) in a sub-montane tropical rainforest in Peninsular Malaysia that is presently experiencing low intensity development. Mixed species flocks in the forest interior and forest edge habitats (9.3 ± 2.3 and 8.4 ± 2.3, respectively) had significantly higher number of species than those observed in the urban habitat (5.1 ± 1.7). Flock participation was influenced by environmental characteristics (e.g., canopy cover). Flocking species sensitive to habitat disturbance were likely to be from the Families Corvidae, Nectariniidae, and Sylviidae; had narrow to restricted altitudinal ranges; and were exclusively dependent on primary forest and understory microhabitats. We conclude that sub-montane mixed species flocks are affected by even small scale urbanization and that they, particularly with species richness as a parameter, can be used as effective ecological indicators. With the looming development pressure on the sub-montane/montane habitats in Peninsular Malaysia and the Southeast Asian region, urgent conservation actions are needed for the preservation of their biotas.     

The effects of forest fragmentation on euglossine bee communities (Hymenoptera: Apidae: Euglossini)

Despite scientific and media attention on pollinator declines, there is still only a rudimentary understanding of the response of bees—the most important group of pollinators worldwide—to ongoing land use changes. Euglossine bees are an ecologically important Neotropical clade of forest-dependent pollinators. Despite the fact that euglossines are well studied relative to other groups of tropical bees, only three previous studies, all from Brazil, address the response of euglossines to forest fragmentation. In this study, I tripled the maximum sample size of previous efforts by sampling male euglossines in 22 forest fragments ranging in area from 0.25 ha to 230 ha in southern Costa Rica, using chemically baited Van Someren traps. Abundance of euglossine bees was significantly positively related to forest fragment size, negatively related to shape (edge:area ratio), and marginally related to fragment isolation. Euglossine species richness showed similar, but weaker trends: richness was significantly positively related to the quantity of forest edge, marginally negatively related to fragment area, and not related to fragment isolation. The positive relationship between euglossine richness and abundance and forest fragment edge is consistent with other studies that have found high euglossine density in secondary or disturbed forest. The data suggest that individual euglossines move between forest fragments, as has been shown in other systems. Still, forest fragmentation appears to affect euglossine bees more strongly than other bee groups in the study region. Their large flight range and positive relationship with forest edges may help to buffer the negative effects of fragmentation, allowing euglossines to utilize even the very smallest forest fragments in the study area.     

Peat swamp forest avifauna of Central Kalimantan, Indonesia: Effects of habitat loss and degradation

Peat swamp forest is a unique wetland ecosystem covering extensive areas in Southeast Asia that has received relatively little scientific attention and is now being lost at a rapid pace. This study examines the effects of anthropogenic degradation on bird communities in disturbed peat swamp forest habitats – namely, intact logged forest, a degraded forest fragment, and non-forest regrowth – in Central Kalimantan, Indonesia. Results show that species richness was significantly higher and species composition significantly different in intact logged forest in comparison to the degraded forest fragment and non-forested area. Nectarivore and tree foliage-gleaning insectivore abundance declined outside the intact forest, while the regrowth was dominated by the yellow vented bulbul, an open country insectivore–frugivore. Surveys reveal that large intact tracts of logged peat swamp forest can harbour threatened and near threatened bird species (36% of records) and thus play a role in their conservation, especially for a few habitat specialists. Given the extent of unmanaged degraded peatlands and continuing pressure to development them, urgent conservation actions are needed to rehabilitate and protect this ecosystem.     

Lowland rainforest avifauna and human disturbance: persistence of primary forest birds in selectively logged forests and mixed-rural habitats of southern Peninsular Malaysia

We compared the composition and structure of primary forest avifauna among primary forests, selectively logged forests and mixed-rural areas (e.g. villages and agricultural areas) of Peninsular Malaysia. We found that forests that were selectively logged at least 30 years ago contained only 73-75% of the 159 species of extant primary forest birds, with an increased proportion of dominant species. We estimated that only 28-32% of the primary forest species utilized the mixed-rural habitat, and that the number of species that bred in the agricultural landscapes might be even lower. The microhabitat of different species most affected their vulnerability to disturbance. Most small, arboreal frugivores and omnivores, and insectivores that fed from tree trunks, showed greater persistence in the mixed-rural habitat than ground dwelling bird species, which were affected most by disturbance. Resource abundance and variables that were closely related to forest disturbance such as the density of large trees, density of dead trees, canopy cover density and shrub volume influenced the distribution of the primary forest birds. Large primary forest reserves and a revision of short-cycle logging regimes (ca. 30 years) are needed if we are to conserve the lowland rainforest avifauna of Peninsular Malaysia and other parts of Southeast Asia.     

Effects of forest fragmentation on the granivory of differently sized seeds

The Maulino forest is a unique temperate ecosystem restricted to a small range of the coast of central Chile. This forest harbors many endemic species, and is threatened due to intensive deforestation and fragmentation. Currently the Maulino forest is composed of a suite of small fragments scattered in a landscape dominated by exotic plantations. The fragmentation of the Maulino forest has resulted in a higher abundance of granivores in small forest fragments compared with continuous forest. In order to determine if fragmentation-induced changes in granivore abundance affects the granivory of different size seeds, we experimentally assessed seed predation of a large-seeded species [Nothofagus glauca (Phil.) Krasser] and a small-seeded species [Nothofagus obliqua (Mirbel) Oersted] in the edges and interior of one continuous (large) forest and three small fragments (∼3 ha) surrounded by plantations of the exotic tree Pinus radiata. To determine what kind of granivores are preying upon seeds, seeds of both species were excluded from and exposed to large and small granivores. Granivory was higher in small fragments than in continuous forest, higher in the edges than in the forest interior, and higher upon large than on small seeds. Rodents, which were more abundant in forest fragments, were the main consumers. Thus, fragmentation indeed affects granivory increasing the consumption of seeds by predators inhabiting the Maulino forest remnants or coming from the matrix. This change may affect the future structure of the tree community in forest fragments.     

A multi-region assessment of tropical forest biodiversity in a human-modified world

The fate of much of the world’s terrestrial biodiversity is linked to the management of human-modified forest landscapes in the humid tropics. This Special Issue presents the first pan-tropical synthesis of research on the prospects for biodiversity in such systems, with eight individual regional summaries covering Mesoamerica, Amazonia, Atlantic forest of South America, West Africa, Madagascar, Western Ghats, Southeast Asia and Oceania. Two additional papers compare the state of conservation science in tropical forests with both temperate forests and savannah systems. This overview paper provides a comparative analysis of the threats and opportunities facing tropical forest biodiversity, thereby helping to identify the most pressing areas of future research and region-specific factors that contribute towards the effectiveness of individual conservation initiatives. While many of the threats facing tropical forest biodiversity are commonplace they vary markedly in their relative importance across different regions. There is a critical lack of comparable data to understand scale dependent processes, or the relative importance of varying geographic and historical contexts in determining present-day patterns. Conservation science has a key role to play in safeguarding the future of tropical forest biodiversity, but needs to become more effectively embedded in the context of real-world conservation challenges and opportunities. Significant progress can be achieved by improving the cost-effectiveness of research as well as the exchange of ideas and data amongst scientists working in different, often isolated parts of the world. We hope this special issue goes some way top achieving this exchange of knowledge.     

Effects of fragmentation on artificial nest predation in a tropical forest in Kenya

Nest predation has been established as a leading source of reproductive failure in songbirds. Numerous studies, conducted primarily in the Northern Hemisphere, have linked high rates of nest predation with fragmentation and habitat edges. To date, virtually no such studies have been conducted in Tropical Africa. Here we investigate the effects of disturbance level and edge on depredation of artificial avian nests in six fragments of Kakamega Forest, Kenya. We found that nest losses were higher at the edge than in the interior as often reported in previous studies. Surprisingly, nest predation was highest in the least disturbed fragments. One possible explanation for these findings is that top predators are missing from Kakamega Forest, allowing nest predator populations to increase in all fragments, while in the highly disturbed fragments, domestic dogs might be surrogates for top predators. Alternatively, human activity may itself lead to a decline in mesopredator populations.     

Effect of forest fragmentation on fruit and seed predation of the tropical dry forest tree Ceiba aesculifolia

Forests fragmentation reduces the density of natural plant populations forming patches of the remaining individuals. One of the biotic interactions that can be affected by forest fragmentation and is poorly studied is seed predation. We determined the effects of forest fragmentation on seed and fruit predation in Ceiba aesculifolia by comparing trees in continuous forest with trees in fragmented forest. We compared the following variables: (a) frequency of fruit predation by Collie’s squirrel (Sciurus colliaei) in each habitat; (b) frequency of the cotton-staining bug seed predator (Dysdercus, Orden Hemiptera) in each habitat; (c) the effect of seed predation on germination frequency and time; and (d) the effect of different life stages of Dysdercus on seed viability. In continuous habitat, 100% of the trees presented fruits with squirrel predation while only 34% of trees in fragmented habitats presented fruit predation. In continuous forest 27% of the trees contained fruits with the seed predator Dysdercus, while only 2% of the trees in fragmented forest presented Dysdercus. The initial weight of damaged seeds was greater than seeds that were not damaged indicating that seed predators select heavier seeds to feed upon. Frequency of seed germination was affected by different life stages; pre-adults decreased germination significantly more than nymphs and adults. Seed predation significantly increased the time it took for germination to occur. Our study shows that forest fragmentation significantly affects predation patterns of squirrels and cotton-staining bugs. Reduction of natural seed predators in forest fragments may have long-term consequences on forest structure and diversity.     

Importance of reservoirs for the conservation of freshwater molluscs in a tropical urban landscape

Freshwater species and ecosystems are gravely imperiled, particularly within urban landscapes of tropical Asia. In one of the region’s most urbanized landscapes (i.e., Singapore), we determined: (1) the importance of six different habitats (i.e., catchment reservoirs, estuarine reservoirs, forest streams, rural streams, ponds and monsoon canals) for conserving the diversity of freshwater molluscs; (2) key environmental factors (e.g., pH) affecting molluscan distribution; (3) important biogeographical determinants (e.g., area) of molluscan richness within each habitat; and (4) the habitat affinities of introduced species. High sampling saturation was achieved at most study habitats with minimal sampling effort, suggesting that the utilization of molluscs as bioindicators can expedite freshwater conservation initiatives. Estuarine reservoirs (6.0 ± 2.0) had the highest molluscan richness, vis-à-vis catchment reservoirs, forest streams, rural streams, ponds and monsoon canals (3.0 ± 1.5; 0; 3.3 ± 2.0; 1.8 ± 0.5 and 3.5 ± 0.5 respectively). Both reservoir types possessed species compositions distinct from other habitats and contained majority (76%) of the sampled species. Reservoirs therefore serve to conserve the bulk of local freshwater malacofauna, especially if they are maintained at near-neutral pH levels (i.e., ∼7.3) and contain large substrates (i.e., rocks). Area was the best predictor of molluscan richness across all habitats, implying that larger freshwater habitats require higher conservation priorities than smaller ones. Introduced (non-native) species (e.g., Pomacea canaliculata) had high affinities for reservoirs, which are in need of monitoring to curb population expansions. The interminable growth of human settlements urgently requires a reconciliatory approach, which includes the ecologically-sound design and management of modified habitats to complement reserves in sustaining native freshwater species.     

The responses of understorey birds to forest fragmentation, logging and wildfires: An Amazonian synthesis

We combine mist-net data from 24 disturbance treatments taken from seven studies on the responses of understorey Amazonian birds to selective logging, single and recurrent wildfires, and habitat fragmentation. The different disturbance treatments had distinct effects on avian guild structure, and fire disturbance and the isolation of forest patches resulted in bird communities that were most divergent from those in continuous, undisturbed forest in terms of their species composition. Although low-intensity logging treatments had the least noticeable effects, the composition of understorey birds was still markedly different from the composition in undisturbed forest. This analysis demonstrates the importance of preventing habitat fragmentation and the spread of fires in humid tropical forests, and highlights the need for more research to determine the long-term suitability of large areas of degraded forest for forest birds.     

Storage effects on the community level physiological profiles of Mediterranean forest soils

Community level physiological profiles (CLPPs) have been implemented in many European soil monitoring programmes as a rapid tool for the assessment of the functional properties of soil microbial communities. However, this technique has not been harmonized among different laboratories. In this experiment, the changes of the CLPPs after storage of three Mediterranean forest soils were characterised for two sampling depths. The methods to store the samples were cooling, freezing and room temperature storage. Data presented in this study provide evidence that substantial changes can occur to the soil microbial community functions, regardless of the kind of storage. Changes in functional diversity and substrate evenness depended on the profile and sampling depth. The rate of consumption of the groups of substrates, however, shifted towards an enhanced utilisation of carboxylic acids, phenols and/or amines after 1 month storage at 4 °C, regardless of the profile or sampling depth. This was attributed to the physical disruption of soil aggregates and exposure of relatively recalcitrant occluded organic matter. These effects levelled out during 1-year storage. The great sensitivity of CLPPs to storage treatment suggests to take care for immediate analysis after sampling. In case fresh samples are not available, freezing is recommended as a convenient alternative; in that case, however, the kinetic approach is required for data analysis.     

Independent effects of woodland loss and fragmentation on Brown Treecreeper distribution

We examined the influence of local habitat and the surrounding landscape on the distribution of Brown Treecreepers in a matrix of woodlands and pastures. Our goals were to: (1) determine the importance and scale of the independent effects of woodland cover and fragmentation on treecreeper distribution, and (2) employ landscape variables to improve models of treecreeper distribution based on local habitat features. Woodland fragmentation was important at a large scale while both woodland cover and fragmentation were important at a smaller scale. Excluding unoccupied sites in highly fragmented landscapes improved the ability of local habitat features to explain Brown Treecreeper distribution, which appeared to be constrained by cavity density. Brown Treecreepers' response to fragmentation at the larger scale may occur because fragmentation disrupts dispersal. Alternatively, their response may be an example of a general phenomenon of fragmentation effects only arising when < 20% of woodland cover remains at a given scale. As fragmentation increases, so does the need to incorporate landscape patterns into wildlife-habitat models.     

Effects of ground fires on understorey bird assemblages in Amazonian forests

Avifaunal responses to understorey fire disturbance and subsequent changes in habitat structure were examined within 20 burnt and unburnt forest plots of 0.25 ha (10×250 m), 10-15 months after an unprecedented understorey fire swept through the Tapajós-Arapiuns Extractive Reserve of central Brazilian Amazonia following the severe 1997-1998 El-Niño dry season. Although these surface fires in the previously undisturbed primary forest were relatively mild, they resulted in dramatic changes in forest structure consistent with those found elsewhere in Amazonia. Bird species negatively affected by these changes tended to be the least common, the most disturbance-sensitive, and habitat specialists. Considering different guilds, ant followers, dead-leaf gleaners, terrestrial gleaners, and arboreal sallying insectivores were the most negatively affected, whereas nectivores and arboreal granivores became more abundant in the burnt forest. The results highlight the severe consequences of even relatively mild surface fires in neotropical forests, and the importance of controlling haphazard frontier expansion for the conservation of susceptible species that are endemic to fire-prone regions.