Long‐term Changes in Bird Communities after Wildfires in the Central Brazilian Amazon

We examined long‐term responses of an Amazonian bird assemblage to wildfire disturbance, investigating how understory birds reacted to forest regeneration 1, 3, and 10 years after a widespread fire event. The bird community was sampled along the Arapiuns and Maró river catchments in central Brazilian Amazonia. Sampling took place in 1998, 2000, and 2008 using mist‐nets in eight plots (four burned, four unburned sites). Species richness did not change significantly in unburned sites. In burned sites, however, we found significantly lower richness in 1998, higher richness in 2000, and similar richness in 2008. Multi‐dimensional scaling ordination showed consistent differences in bird communities both within burned sites sampled in different sampling years, and between burned and unburned sites in all years. Of the 30 most abundant species, 12 had not recovered 10 years after the fires, including habitat specialists such as mixed flocks specialists and ant‐followers. Fire‐disturbance favored three species (two hummingbirds and a manakin) in the short term only. All other species were either favored throughout the study (seven species of omnivores and small insectivores) or did not show a clear response (eight species). In burned sites, we also found significantly lower abundance of species sensitive to disturbances and habitat specialists over the entire study period. Although the bird community seems to be recovering in terms of richness, the overall community composition and abundance of some species in post‐burned and unburned sites remain very different, and have not recovered after 10 years of forest regeneration.     

Direct and indirect responses of tallgrass prairie butterflies to prescribed burning

Fire is an important tool in the conservation and restoration of tallgrass prairie ecosystems. We investigated how both the vegetation composition and butterfly community of tallgrass prairie remnants changed in relation to the elapsed time (in months) since prescribed fire. Butterfly richness and butterfly abundance were positively correlated with the time since burn. Habitat-specialist butterfly richness recovery time was greater than 70 months post-fire and habitat-specialist butterfly abundance recovery time was approximately 50 months post-fire. Thus, recovery times for butterfly populations after prescribed fires in our study were potentially longer than those previously reported. We used Path Analysis to evaluate the relative contributions of the direct effect of time since fire and the indirect effects of time since fire through changes in vegetation composition on butterfly abundance. Path models highlighted the importance of the indirect effects of fire on habitat features, such as increases in the cover of bare ground. Because fire return intervals on managed prairie remnants are often less than 5 years, information on recovery times for habitat-specialist insect species are of great importance.     

The effect of fire history in shaping diversity patterns of flower-visiting insects in post-fire Mediterranean pine forests

Fire affects diversity and structure of flower-visitor communities. We explored the effect of fire history on the diversity patterns and structure of the flower-visitor guilds (bees, beetles, flies, sawflies, and wasps), across a post-fire regeneration sequence of pine forests in Rhodes Island, Greece. Fire history was defined by fire frequency and post-fire age of sites. We did not find significant differences in species richness and abundance per guild between fire-history regimes except for the abundance of flies, sawflies and the entire flower-visitor community. Fire strongly affected the community structure of bees, beetles, and sawflies. Some of the most abundant and common species responded significantly to fire in terms of abundance; yet, we observed no significant variation in the abundance of the common species of bees, the most prominent pollinator group, implying that provision of pollination services may not be considerably affected by fire. Long-unburnt sites displayed higher heterogeneity in species composition compared to recently-burnt sites (either burnt once or twice). This pattern deviated significantly from null expectations when analyzing the abundance-based metric of β-diversity and was obscure in the case of the presence/absence-based metric, indicating that fire affected mainly the spatial distribution of individuals, i.e. the main change is not due to species turnover but to changes in relative abundance. Furthermore, the species composition in recently-burnt sites (burnt once in 2008) were more similar than in twice-burnt sites (including areas burnt once between 1984 and 1992, and in 2008), indicating that fire frequency affected post-fire heterogeneity of species composition.     

Local lithological drivers of post-fire vegetation recovery and implications for fire-prone regions

Local ecosystem resilience to fire disturbance can be influenced by multiple factors, from topography and climate, to fire history and pre-fire structure of biotic communities. Here we investigated the factors affecting post-fire recovery of scrub vegetation in areas under Mediterranean climate affected by frequent fires. We hypothesized that, under comparable climatic and topographic conditions, geological factors (with bedrock type as a proxy) would be at least as important as fire history in explaining patterns of post-fire recovery. We surveyed scrub vegetation in a mountain study area in Portugal, using a stratified random sampling scheme, with fire frequency, time since last fire, and bedrock type (granite vs. schist) as stratifying layers. Based on vegetation and plant community data from 40 plots, we analyzed total species richness and composition, and the relative abundance of functional groups defined on the basis of general (non fire-specific) life-history traits. We found that, at a local scale, lithology can override fire history in determining post-fire recovery. Vegetation plots on granite exhibited a considerable development of tall scrubs and higher values of total species richness. They also hosted higher numbers of animal-dispersed woody species, of trees and tall scrubs, of woody deciduous species, and of forest, edge and tall scrub species. Differences in the post-fire development of scrub vegetation and in the functional profile of plant communities highlight the need to consider local geological diversity when establishing priorities for post-fire active restoration under scenarios of limited resources.     

Avifaunal responses to habitat fragmentation in the threatened littoral forests of south-eastern Madagascar

Aim Madagascar's lowland forests are both rich in endemic taxa and considered to be seriously threatened by deforestation and habitat fragmentation. However, very little is known about how these processes affect biodiversity on the island. Herein, we examine how forest bird communities and functional groups have been affected by fragmentation at both patch and landscape scales, by determining relationships between species richness and individual species abundance and patch and landscape mosaic metrics. Location Littoral forest remnants within south‐eastern Madagascar. Methods We sampled 30 littoral forest remnants in south‐eastern Madagascar, within a landscape mosaic dominated by Erica spp. heathland. We quantified bird community composition within remnants of differing size, shape and isolation, by conducting point counts in November–December in 2001 and October–November 2002. Each remnant was characterized by measures of remnant area, remnant shape, isolation, and surrounding landscape complexity. We used step‐wise regression to test the relationship between bird species richness and landscape structural elements, after correcting for sampling effort. Relationships between bird species abundances and the landscape variables were investigated with Canonical Correspondence Analysis and binomial logistic regression modelling. Results Bird species richness and forest‐dependent bird species richness were significantly (P < 0.01) explained by remnant area but not by any measure of isolation or landscape complexity. The majority of forest‐dependent species had significant relationships with remnant area. Minimum area requirements for area‐sensitive species ranged from 15 to 150 ha, with the majority of species having area requirements > 30 ha. Surprisingly, there was no relationship between bird body size and minimum area requirement. Forest‐dependent canopy insectivorous species and large canopy frugivorous species were the most sensitive functional groups, with > 90% species sensitivity within each group. The distribution of four forest‐dependent species also appeared to be related to remnant shape where remnant area was < 100 ha. Main conclusions The majority of forest‐dependent species, including many that are considered widespread and common, were found to have significant relationships with fragment size, indicating that they are sensitive to processes associated with habitat loss and fragmentation. As deforestation and habitat fragmentation remain serious problems on the island, it follows that many forest‐dependent bird species will decline in abundance and become locally extinct. At the regional scale, we urge that large (> 200 ha) blocks of littoral forest are awarded protected status to preserve their unique bird community.     

Temporal changes in the breeding bird community caused by post-fire treatments after the Samcheok forest fire in Korea

The Samcheok forest fire of April 2000 was the biggest stand-replacing fire recorded in Korea, and led to the largest-scale salvage logging operation (performed until 2005) ever implemented. We investigated the effects of the treatments performed after the fire on the breeding bird community in 2002–2005 (the management period) and 2006–2008 (the post-management period). A total of 75 line transect surveys resulted in 660 detections of 54 species in undisturbed stands (CO), in burned and naturally restored stands (NI), and in burned and logged stands (IT). Four species (Parus major, Aegithalos caudatus, Dendrocopos kizuki, and Parus ater) were identified as indicator species in CO which showed no temporal changes in bird communities and habitat structure. Among the various stand treatments, the standardized species richness was highest in CO (11.6 ± 4.6 species/transect in 2002–2005, 12.1 ± 3.5 in 2006–2008), and this richness did not change over time. On the other hand, low richness was observed in NI (6.8 ± 2.6 in 2002–2005, 9.6 ± 2.3 in 2006–2008), and the lowest richness was seen in IT (5.0 ± 2.4 in 2002–2005, 6.1 ± 1.8 in 2006–2008), but both of these increased over time. Although the bird abundances in NI and IT were lower than those in CO (38.0 ± 27.7 birds/transect in 2002–2005, 31.3 ± 10.9 in 2006–2008), the abundances in NI (15.1 ± 8.6 in 2002–2005, 17.6 ± 11.4 in 2006–2008) and IT (11.7 ± 8.3 in 2002–2005, 10.0 ± 4.6 in 2006–2008) were not significantly different. There was no significant difference in abundance between time periods for any of the stand treatments. These results imply that NI (i.e., no salvage logging) allows greater bird richness but not abundance to be recovered compared to IT. No indicator species was consistently present in NI throughout the two time periods covered due to the rapid regrowth of vegetation, but four open-habitat dwellers (Falco tinnunculus, Phoenicurus auroreus, Emberiza cioides, and Sturnus cineraceus) colonized IT during the post-management period. The bird assemblage in IT, as assessed by canonical correspondence analysis, shifted to open habitats, while the avifauna in NI became similar to that in CO over time. While post-fire treatment can provide new colonization opportunities for open-habitat dwellers, the slow colonization process, the low species richness, and the low bird abundance observed in large areas of IT indicate that post-fire treatment using salvage logging inhibits the restoration of forest bird communities by producing a poorer breeding bird community that is very different from the original one. Based on these lessons from the response to the Samcheok forest fire, we suggest that preserving as much of the disturbed forest as possible is essential, and that the current approach to post-fire treatment—intensive salvage logging—needs to be revised to ensure the effective restoration of breeding bird communities in disturbed temperate pine forests.     

Evaluating the role of fire disturbance in structuring small reptile communities in temperate forests

Fire is an integral disturbance shaping forest community dynamics over large scales. However, understanding the relationship between fire induced habitat disturbance and biodiversity remain equivocal. Ecological theories including the intermediate disturbance hypothesis (IDH) and the habitat accommodation model (HAM) offer predictive frameworks that could explain faunal responses to fire disturbances. We used an 80 year post-fire chronosequence to investigate small reptile community responses to fires in temperate forests across 74 sites. First, we evaluated if changes in species richness, abundance and evenness post-fire followed trends of prior predictions, including the IDH. Second, using competing models of fine scale habitat elements we evaluated the specific ways which fire influenced small reptiles. Third, we evaluated support for the HAM by examining compositional changes of reptile community post-fire. Relative abundance was positively correlated to age post-fire while richness and evenness showed no associations. The abundance trend was as expected based on the prior prediction of sustained population increase post-disturbance, but the trend for richness contradicted the prediction of highest diversity at intermediate levels of disturbance (according to IDH). Abundance changes were driven mainly by changes in overstorey, ground layer, and shelter, while richness and evenness did not associate with any vegetation parameter. Community composition was not strongly correlated to age since fire, thus support for the HAM was weak. Overall, in this ecosystem, frequent fire disturbances can be detrimental to small reptiles. Future studies utilizing approaches based on species traits could enhance our understanding of biodiversity patterns post-disturbance.     

The effects of fire on communities,guilds and species of breeding birds in burnt and control pinewoods in central Italy

Breeding bird communities in burnt and unburnt residual pinewoods were studied over 3 years by line-transect method, following a catastrophic fire event in Castelfusano (Rome, Central Italy; July 2000). We applied bootstrap procedures to evaluate whether the observed data were true or just produced by chance, and then examined the emerging patterns at three levels: community, guild and species levels. At the community level, fire acted on breeding bird communities by altering especially the total abundance patterns: the species abundance decreased in the burnt pinewood compared to the residual one, but other parameters were not significantly affected by fire. As a consequence of fire, the destruction and structural simplification of the canopy and shrubby component, as well as the increase of edge habitat and patchiness at landscape scale, induced a turnover in species between pinewoods. Species turnover was higher at the burnt than at the residual pinewoods, during all the 3 years of study. At the guild level, the forest species decreased strongly in terms of richness and abundance in the burnt pinewoods, contrary to the edge and open habitat species which increased in terms of richness, abundance and evenness. Edge species showed the highest turnover in burnt pinewood during the whole period of study. At species level, after an a priori subdivision (based on bibliographic search) of the various species in two ecological guilds (forest versus edge species), it was found that an a posteriori statistical analysis confirmed the expected trend, i.e. that the species which decreased significantly in burnt pinewood were essentially the forest species, whereas the species which increased were essentially the edge/open habitat ones. Overall, in order to investigate the effects of fire catastrophes on birds, the guild approach seems more exhaustive than the taxonomic community approach, where intrinsic confounding trends are present.     

Introduced birds in urban remnant vegetation: Does remnant size really matter?

Abstract Introduced birds are a pervasive and dominant element of urban ecosystems. We examined the richness and relative abundance of introduced bird species in small (1–5 ha) medium (6–15 ha) and large (>15 ha) remnants of native vegetation within an urban matrix. Transects were surveyed during breeding and non‐breeding seasons. There was a significant relationship between introduced species richness and remnant size with larger remnants supporting more introduced species. There was no significant difference in relative abundance of introduced species in remnants of different sizes. Introduced species, as a proportion of the relative abundance of the total avifauna (native and introduced species), did not vary significantly between remnants of differing sizes. There were significant differences in the composition of introduced bird species between the different remnant sizes, with large remnants supporting significantly different assemblages than medium and small remnants. Other variables also have substantial effects on the abundance of introduced bird species. The lack of significant differences in abundance between remnant sizes suggests they were all equally susceptible to invasion. No patches in the urban matrix are likely to be unaffected by introduced species. The effective long‐term control of introduced bird species is difficult and resources may be better spent managing habitat in a way which renders it less suitable for introduced species (e.g. reducing areas of disturbed ground and weed dominated areas).     

Effects of prescribed fire on an ant community in Florida pine savanna

Abstract.  1. The effects of prescribed fire on ant community structure were examined in a regenerating longleaf pine savanna in Florida, U.S.A. The presence of ants on 20, 10 × 10 m plots was determined by baiting every 1–3 months from 18 months before a fire until 6 months afterwards.
2. Expected species richness (based on rarefaction) and species density 6 months post-fire were significantly lower than for the same month (September) 6 months before the fire.
3. Cluster analysis revealed that the effects of fire were far less important predictors of ant community structure than seasonality and unexplained inter-annual variation. Thus, overall, the impacts of fire were relatively minor and short term at the community level.
4. Different functional groups of ants (as defined by Andersen, 1997) responded to fire in strikingly different ways. Generalised Myrmicinae (e.g. Pheidole spp., Monomorium viride ) were affected more severely by fire than were the other functional groups. In contrast, the dominant Dolichoderinae ( Forelius pruinosus ) exhibited a large increase after the fire and seemed to be responsible for the decline in abundance of several species.
5. A strong negative correlation between F. pruinosus and other groups of ants immediately after the fire suggested more intense competition among ants at that time. Six months post-fire, the abundance of F. pruinosus decreased markedly and the abundance of other species rebounded.
6. The rapid post-fire recovery of the ant community probably reflects adaptations of ants to a chronic fire regime.     

Recurrent fires and environment shape the vegetation in Quercus suber L. woodlands and maquis

The effects of fire recurrence on vegetation patterns in Quercus suber L. and Erica-Cistus communities in Mediterranean fire-prone ecosystems of south-eastern France were examined on stands belonging to 5 fire classes, corresponding to different numbers of fires (from 0 to 4) and time intervals between fires since 1959. A common pool of species was identified among the plots, which was typical of both open and closed maquis. Fire recurrence reduced the abundance of trees and herbs, whereas it increased the abundance of small shrubs. Richness differed significantly between the most contrasting classes of fire recurrence, with maximal values found in control plots and minimal values in plots that had burned recurrently and recently. Equitability indices did not vary significantly, in contrast to Shannon's diversity index which mostly correlated with richness. Forest ecosystems that have burnt once or twice in the last 50 years were resilient; that is to say they recovered a biomass and composition similar to that of the pre-fire state. However, after more than 3-4 fires, shrubland communities displayed lower species richness and diversity indices than unburned plots. The time since the last fire and the number of fires were the most explanatory fire variables, governing the structure of post-fire plant communities. However, environmental factors, such as slope or exposure, also made a significant contribution. Higher rates of fire recurrence can affect the persistence or expansion of shrublands in the future, as observed in other Mediterranean areas.     

Avifauna associated with ephemeral ponds on the Cumberland Plateau, Tennessee

ABSTRACT.   Although ephemeral ponds act as small hotspots of plant, invertebrate, and salamander diversity, the importance of such ponds for birds has been little studied. We hypothesized that ephemeral ponds on the Cumberland Plateau in Tennessee would support a greater abundance, richness, and diversity of birds than the surrounding hardwood forests. In 2004, we recorded all birds seen or heard in 10 min within 50-m radius circles at 25 ephemeral ponds. We repeated the counts at control sites located 150 m from each pond in the surrounding forest. To quantify potential food availability, we captured aerial invertebrates using sweep nets at four points around a subsample of eight ephemeral ponds and at an equal number of control sites. We found significantly greater bird abundance, richness, and species diversity at ephemeral ponds than at control sites, and that pond area was not associated with either bird abundance or richness. Bird community composition at pond and control sites was similar. Aerial invertebrates were significantly more abundant at ephemeral ponds than at adjacent forest sites, providing one possible explanation for greater bird abundance at ephemeral ponds.     

Conservation value for birds of traditionally managed isolated trees in an agricultural landscape of Madagascar

Isolated trees have distinctive economic, social and cultural value for the Betsileo people living on the edge of the protected forest corridor between Ranomafana and Andringitra national parks, in South-East Madagascar. Many of these trees are Ficus spp., traditionally protected and respected. At the landscape level, they are isolated features in a heterogeneous mosaic, providing fruit, shade and aesthetic services in open cultivated areas. Within the current management system, isolated trees may also contribute significantly to the provision of ecological services by enhancing bird diversity in open areas outside the forest. We identified practices and values linked to isolated tree uses and management through ethnographic data collection. Bird presence and abundance were sampled by 338 point counts in isolated trees and open areas of the agricultural mosaic. Isolated trees were occupied by 18 out of 32 (56%) bird species in the agricultural mosaic, including 8 (25%) endemic forest species. Endemic forest birds were significantly more numerous in isolated trees than in open habitats, both in species richness and abundance (mean P value < 0.001). Overall bird species richness was significantly higher in open areas containing isolated trees, than in areas without isolated trees. Bird species richness in Ficus spp. was significantly higher than in other isolated tree species, although no differences were detected in abundance or within guilds. Community-based management of isolated trees may thus represent an opportunity for convergence between bird conservation goals outside protected areas and local management values and practices.     

Does size really matter? Species–area relationships in human settlements

Aim To describe species–area relationships in human settlements and compare them with those from a non‐urban habitat. Location West‐central Mexico. Methods We surveyed breeding birds in 13 human settlements and five shrubland patches. We estimated bird species richness using an abundance‐based coverage estimator with equal sample sizes to eliminate biases related to sampling effort differences. To assess species–area relationships, we performed log–log linear regressions between the size of the studied patches and their estimated bird richness. We also used a logarithmic approach to determine how the species–area relationship asymptoted and made use of the Michaelis–Menten model to identify the size at which the studied patches reached their maximum species richness. We also investigated (1) possible relationships among the estimated bird richness and other variables known to affect urban‐dwelling birds (built cover, plant species richness, tree cover or human population density) and (2) changes in bird community composition related to the size of the studied human settlements. Results Species–area relationships exhibited different patterns among the studied habitats. The log–log regression slope was steeper in human settlements, while the intercept was higher in shrublands. The maximum number of species was more than twofold higher in shrublands. Human settlement patch size was the only variable significantly related to bird richness. Our community composition results show that two main bird groups are related to human settlement size, and that as the size of human settlements increases, bird community similarity in relation to the largest city increases. Main conclusions Human settlements act as ecological islands, with pronounced species–area relationships. Our results suggest that an important threshold for bird species richness and community composition is reached in human settlements > 10.2 km². This threshold is unlikely to be generalizable among bio‐regions, and thus should be quantified and considered when studying, managing and/or planning urban systems.     

A multivariate model of plant species richness in forested systems: old-growth montane forests with a long history of fire

Recently, efforts to develop multivariate models of plant species richness have been extended to include systems where trees play important roles as overstory elements mediating the influences of environment and disturbance on understory richness. We used structural equation modeling to examine the relationship of understory vascular plant species richness to understory abundance, forest structure, topographic slope, and surface fire history in lower montane forests on the North Rim of Grand Canyon National Park, USA based on data from eighty‐two 0.1 ha plots. The questions of primary interest in this analysis were: (1) to what degree are influences of trees on understory richness mediated by effects on understory abundance? (2) To what degree are influences of fire history on richness mediated by effects on trees and/or understory abundance? (3) Can the influences of fire history on this system be related simply to time‐since‐fire or are there unique influences associated with long‐term fire frequency? The results we obtained are consistent with the following inferences. First, it appears that pine trees had a strong inhibitory effect on the abundance of understory plants, which in turn led to lower understory species richness. Second, richness declined over time since the last fire. This pattern appears to result from several processes, including (1) a post‐fire stimulation of germination, (2) a decline in understory abundance, and (3) an increase over time in pine abundance (which indirectly leads to reduced richness). Finally, once time‐since‐fire was statistically controlled, it was seen that areas with higher fire frequency have lower richness than expected, which appears to result from negative effects on understory abundance, possibly by depletions of soil nutrients from repeated surface fire. Overall, it appears that at large temporal and spatial scales, surface fire plays an important and complex role in structuring understory plant communities in old‐growth montane forests. These results show how multivariate models of herbaceous richness can be expanded to apply to forested systems.     

Seasonal Incidence and Diversity Pattern of Avian Communities in the Bangalore University Campus,India

The present study deals with the species abundance, diversity and species richness of avian communities in the Bangalore University Campus (BUC), Bengaluru, India. One hundred and six species of birds belonging to 42 families under 68 genera were recorded. Shannon–Wiener’s and Fisher’s alpha diversities, species evenness, species richness of bird communities, number of bird species and percentage of population density of birds between various seasons in the BUC differed significantly between the study years. Of these bird species, the relative abundance (6.96 %) and species distribution ratio (0.070) of Psittacula krameri were highest, whereas relative abundance (0.04 %) and species distribution ratio (0.002) of Coracias benghalensis were lowest. The existing 32 species of flowering plants/trees belonging to 29 genera under 14 families in the campus are used for perching by birds. Moreover 29 species of flowering plants/trees belonging to 24 genera under 16 families depend on birds for pollination and/or seed dispersal. Occurrence of greater bird diversity and abundance of avian communities were recorded highest in the winter season in the BUC premises. In the different seasons, the BUC had varying community structure of birds between the study years. BUC suffers from numerous threats namely grass cutting, fire and grazing of domestic animals. Conservation methods needed for habitat management are restoration of vegetation and wetlands, and increase plant and tree diversity to protect the ecosystem of BUC habitat and to preserve its diversity of avifauna.     

Footnote on Breeding of Paradise Flycatcher

Bird community diversity was assessed in semi-arid savanna in the Northern Cape province of South Africa and related to vegetation diversity and foliage height diversity. As this is an area in which shrub encroachment is common, the effects of shrub or bush encroachment on bird species diversity were specifically addressed. An experiment in which the dominant encroaching species, Acacia mellifera, was removed from ten 1 ha plots was used and compared with ten controls. A strong positive association with foliage height diversity was shown. No effect of experimental removal of the dominant encroacher, A. mellifera, on bird species diversity or species richness was found. However, four species increased in relative abundance in cut plots and two species decreased in relative abundance in these plots.     

Conserving long unburnt vegetation is important for bird species,guilds and diversity

Landscape-level wildfires have a major role in structuring faunal assemblages, particularly in fire-prone landscapes. These effects are mediated by changes to vegetation structure and composition that directly influence the availability of shelter, feeding and breeding resources. We investigated the response of a semi-arid shrubland bird community in Western Australia to the prevailing fire regime by examining the abundance, diversity and guild structure in relation to time since fire. We also examined vegetation structural attributes in relation to time since fire. We surveyed 32 sites ranging in age from 12 to 84 years since last fire. A total of 845 birds from 40 species were recorded. Vegetation structure varied with fire history with old and very old sites characterised by less bare ground, more leaf litter cover and greater canopy cover. Bird community composition varied with time since fire, driven by increased bird species richness and abundance of insectivores, granivores/frugivores, golden whistlers, grey shrike-thrush and red-capped robins with time since fire. Frequent, intense landscape-scale fires transform the landscape into homogeneous young shrublands, which may render vegetation unsuitable for several species and guilds.     

Effects of habitat transitions on rainforest bird communities across an anthropogenic landscape mosaic

We compared bird community responses to the habitat transitions of rainforest‐to‐pasture conversion, consequent habitat fragmentation, and post‐agricultural regeneration, across a landscape mosaic of about 600 km² in the eastern Australian subtropics. Birds were surveyed in seven habitats: continuous mature rainforest; two size classes of mature rainforest fragment (4–21 ha and 1–3 ha); regrowth forest patches dominated by a non‐native tree (2–20 ha, 30–50 years old); two types of isolated mature trees in pasture; and treeless pasture, with six sites per habitat. We compared the avifauna among habitats and among sites, at the levels of species, functional guilds, and community‐wide. Community‐wide species richness and abundance of birds in pasture sites were about one‐fifth and one‐third, respectively, of their values in mature rainforest (irrespective of patch size). Many measured attributes changed progressively across a gradient of increased habitat simplification. Rainforest specialists became less common and less diverse with decreased habitat patch size and vegetation maturity. However, even rainforest fragments of 1–3 ha supported about half of these species. Forest generalist species were largely insensitive to patch size and successional stage. Few species reached their greatest abundance in either small rainforest fragments or regrowth. All pastures were dominated by bird species whose typical native habitats were grassland, wetland, and open eucalypt forest, while pasture trees modestly enhanced local bird communities. Overall, even small scattered patches of mature and regrowth forest contributed substantial bird diversity to local landscapes. Therefore, maximizing the aggregate rainforest area is a useful regional conservation strategy.     

Too risky to settle: avian community structure changes in response to perceived predation risk on adults and offspring

Predation risk is widely hypothesized as an important force structuring communities, but this potential force is rarely tested experimentally, particularly in terrestrial vertebrate communities. How animals respond to predation risk is generally considered predictable from species life-history and natural-history traits, but rigorous tests of these predictions remain scarce. We report on a large-scale playback experiment with a forest bird community that addresses two questions: (i) does perceived predation risk shape the richness and composition of a breeding bird community? And (ii) can species life-history and natural-history traits predict prey community responses to different types of predation risk? On 9 ha plots, we manipulated cues of three avian predators that preferentially prey on either adult birds or offspring, or both, throughout the breeding season. We found that increased perception of predation risk led to generally negative responses in the abundance, occurrence and/or detection probability of most prey species, which in turn reduced the species richness and shifted the composition of the breeding bird community. Species-level responses were largely predicted from the key natural-history trait of body size, but we did not find support for the life-history theory prediction of the relationship between species'' slow/fast life-history strategy and their response to predation risk.