Avian Community Response Research Articles

Using a multifaceted approach to reveal avian community responses to natural and anthropogenic effects in a fragmented Southern Mistbelt Forest system, South Africa

Using a multifaceted approach to reveal avian community responses to natural and anthropogenic effects in a fragmented Southern Mistbelt Forest system, South Africa

Avian community response to a novel environment: Commercial forestry in the Campos grasslands of South America

Establishing commercial tree plantations in native grassland ecosystems introduces a different structural and functional vegetation cover type, with expected implications for biodiversity. To better understand biodiversity responses to afforestation, we conducted a resource-use study with birds as a focal group, during the 2013–2014 breeding season in the Northern Campos grasslands of Uruguay. We sampled birds in native environments and plantations of loblolly pine (Pinus taeda) and flooded gum (Eucalyptus grandis) at different rotation stages. We recorded 103 species during 1,573 visits (10-min, 50-meter radius point counts) to 570 stratified sampling units. Native grasslands and forests exhibited greater diversity and had greater variability in species composition than structurally homogeneous plantations. Avian communities in plantations had distinct species combinations and relative abundances not found in native conditions. Avian communities in older plantations were more similar to native forests while those of newly-planted stands were more like grasslands. However, plantations were dominated by habitat generalists and some forest-dependent species, with negligible use by grassland specialist birds. Our results suggest the best conservation opportunities for grassland-dependent birds in afforested systems of the Campos of Uruguay may depend on diverse landscape-level measures rather than stand-level management practices. Albeit our research constituted a comprehensive assessment of bird taxonomic alpha and beta diversity, research on complementary diversity facets and multi-scale resource selection and demographic studies are needed to better understand the fitness implications for conserving and managing grassland birds in afforested landscapes.

Composition of ‘fast–slow’ traits drives avian community stability over North America

AbstractRapid biodiversity loss has triggered decades of research on the relationships between biodiversity and community stability. Recent studies highlighted the importance of species traits for understanding biodiversity–stability relationships. The species with high growth rates (‘fast’ species) are expected to be less resistant to environmental stress but recover faster if disturbed; in contrast, the species with slow growth rates (‘slow’ species) can be more resistant but recover more slowly if disturbed. Such a ‘fast–slow’ trait continuum provides a new perspective for understanding community stability, but its validity has mainly been examined in plant communities. Here, we investigate how ‘fast–slow’ trait composition, together with species richness and environmental factors, regulate avian community stability at a continental scale.We used bird population records from the North American Breeding Bird Survey during 1988–2017 and defined avian community stability as the temporal invariability of total community biomass. We calculated species richness and the community–weighted mean (CWM) and functional diversity (FD) of four key life‐history traits, including body size, nestling period (i.e. period of egg incubation and young bird fledging), life span and clutch size (i.e. annual total number of eggs). Environmental factors included temperature, precipitation and leaf area index (LAI).Our analyses showed that avian community stability was mainly driven by the CWM of the ‘fast–slow’ trait. Communities dominated by ‘fast’ species (i.e. species with small body size, short nestling period and life span and large clutch size) were more stable than those dominated by ‘slow’ species (i.e. species with large body size, long nestling period and life span and small clutch size). Species richness and the FD of the ‘fast–slow’ trait explained much smaller proportions of variation in avian community stability. Temperature had direct positive effects on avian community stability, while precipitation and leaf area index affected community stability indirectly by influencing species richness and trait composition.Our study demonstrates that composition of ‘fast–slow’ traits is the major biotic driver of avian community stability over North America. Temperature is the most important abiotic factor, but its effect is weaker than that of the ‘fast–slow’ trait. An integrated framework combining ‘fast–slow’ trait composition and temperature is needed to understand the response of avian communities in a changing environment.A freePlain Language Summarycan be found within the Supporting Information of this article.

Response of avian communities to edges of tropical montane forests: Implications for the future of endemic habitat specialists

Tropical montane landscapes harbor diverse flora and fauna, and many species there are ecological specialists with narrow elevational distributions, limited geographic ranges, and small global populations. Along elevational gradients, environmental conditions and community composition change dramatically over small spatial scales. As forests are disturbed and edges formed with modified habitat, natural communities could be affected differently across elevations by the many physical and biotic changes at edges. We asked whether forest edges produced altered patterns of avian species composition along a cloud forest - dry forest gradient on the Pacific slope of the Tilarán mountains in Monteverde, Costa Rica. A strong moisture gradient produces cloud forests near the ridgetops, with a concentration of species endemic to the Costa Rica – Panama highlands that are habitat specialists. We conducted 552 point counts across 110 locations from 1100 to 1800 m elevation, yielding 6586 detections of 115 species in 10 km2 of montane forest. We analyzed differences in species composition and single-species abundances between interior and near-edge forest habitats for species grouped by geographic range size. Species composition changed markedly from forest edge to interior in cloud forest habitats, but not in drier forests downslope. Endemic species, especially in cloud forest, were detected less frequently in mature forest near edges than in mature forest interior, and this difference was more pronounced than for cosmopolitan species. On tropical mountainsides, we can expect habitat-specialist endemic species to be more sensitive to further habitat modification. This sensitivity could limit the resilience of tropical bird communities.

The role of learning, acoustic similarity and phylogenetic relatedness in the recognition of distress calls in birds

Many groups of vertebrates produce distress calls when attacked by predators as a last attempt to survive. However, few studies investigate whether recognition of distress calls involves learning or acoustic similarity to familiar calls. This study assesses the importance of these two factors as well as phylogenetic relatedness in distress call recognition by tropical rainforest birds. We measured the avian community responses to familiar and unfamiliar distress calls in a lowland tropical rainforest in Costa Rica using playbacks of a sympatric species, the orange-billed sparrow, Arremon aurantiirostris , and a closely related allopatric species, the white-eared ground-sparrow, Melozone leucotis . In addition, to test whether recognition is driven by phylogenetic relatedness to the call sender, we compared the phylogenetic distance of approaching individuals to A. aurantiirostris when using different playback stimuli. We found that individuals called back to sympatric and allopatric calls within similar amounts of time, supporting the role of acoustic similarity in distress call recognition. We also found that individuals approached faster and spent more time inside the observation zone for sympatric distress calls than for allopatric distress calls, and both responses were stronger than the response to white noise (control), which supports the roles of acoustic similarity and learning in distress call recognition. Sympatric distress calls elicited approaching reactions from species that were more closely related to the sympatric species than did white noise, which suggests that phylogenetically related species are more likely to identify and respond to the sympatric distress signaller, while white noise elicited responses from a random subset of species that were on average more distantly related to the sympatric signaller. We conclude that learning, acoustic similarity and phylogenetic relatedness play important roles in the response to distress calls. • We performed a playback experiment of distress calls in a Neotropical forest. • We compared responses to sympatric and allopatric species' distress calls. • Both learning and acoustic similarity played a role in distress call recognition. • Species related to the distress signaller were more likely to respond to the calls.

Avian community response to landscape-scale habitat reclamation

Reclamation projects encompassing more than several square kilometers (hereafter; landscape-scale) are a recommended strategy to mitigate the impacts of energy development on wildlife. However, the response of wildlife to landscape-scale reclamation remains largely undocumented. Oil and gas developments have contributed substantially to the loss and degradation of sagebrush ecosystems in North America. Management agencies are prioritizing habitat reclamation to mitigate habitat loss with an assumed benefit to wildlife, including songbirds. To determine the influence of landscape-scale habitat reclamation on songbirds, we measured avian species abundance and community composition in sagebrush habitats across a gradient of energy development: 1) active oil and gas, 2) landscape-scale reclamation, and 3) undisturbed sagebrush, in northeastern Wyoming, USA (2016–2018). We modeled the influence of treatment (active, reclaimed, and control), and key habitat variables on songbird abundance using a Bayesian hierarchical approach. We also assessed differences in community composition across treatments using the rarity-weighted richness estimate and the Jaccard Similarity Index. Reclamation efforts had a measurable influence on some species abundance. Human-commensal species increased in abundance with increasing disturbance, which may have increased species richness and rarity in our active and reclaimed sites. The community composition in reclaimed areas more closely resembled undeveloped habitat (control), than active development areas. Terrain roughness was the most consistently influential variable on abundance, and we recommend that this often overlooked habitat variable be included in future studies. The habitat variables that represent where we can most easily target reclamation efforts (e.g., herbaceous cover) had minimal influence on abundance.

Avian community response to experimental forest management

AbstractIn recent decades, concern for migratory birds has stimulated research assessing the relationships between forest management and bird populations. The Missouri Ozark Forest Ecosystem Project (MOFEP) is a long‐term, landscape‐scale experiment designed to examine the effects of even‐aged (i.e., clearcutting), uneven‐aged (i.e., selection cutting), and no‐harvest forest management on ecosystem‐level processes. The management systems were randomly assigned to three sites each (mean area = 400 ha) with harvest occurring on a different portion of trees every 15 yr over a 100‐yr rotation. We used non‐metric multidimensional scaling and linear mixed models to investigate the effects of silvicultural treatment and year‐since‐harvest on bird communities over a 24‐yr period, before and after two harvests (1996 and 2011). Bird community compositions diverged among treatments immediately post‐harvest, but the differences in community composition and structure began to diminish by 8 yr post‐harvest. Species richness was higher in treated stands than no‐harvest controls and lowest approximately 10 yr post‐harvest regardless of treatment. Species diversity showed a linear decrease with year‐since‐harvest. Our findings demonstrate that even‐aged and uneven‐aged forest management can affect bird community composition and structure within the early post‐harvest period, but differences may diminish relatively quickly as harvested stands regenerate. We recommend using a variety of silvicultural methods to provide the diversity of habitats needed for the conservation of diverse forest bird communities.

The Greener the Better! Avian Communities Across a Neotropical Gradient of Urbanization Density

Urbanization has been recognized as one of the most widespread threats to biodiversity. However, the response of wildlife to urbanization differs among groups, with many species being able to persist, adapt, and even thrive in these novel ecosystems. With the aim of assessing the response of avian communities in a neotropical green city, we evaluated their species richness and composition across a gradient of urbanization density comprised by a citywide survey performed in two consecutive years and considering both breeding and non-breeding seasons. As expected, species richness decreased with urbanization. Species loss was drastic when considering data from both years and both seasons, and gradual when seasons were assessed separately. Avian composition for both years and seasons differed largely between the less urbanized and the more urbanized sites, whereas sites with intermediate built cover showed to be more similar to each other. When evaluating avian composition by season in both years, highest differences were recorded between more urbanized sites and all other studied sites, while less urbanized sites showed high similarity regardless of the surveyed season. Sites with intermediate built cover had higher similarity among seasons, showing that such conditions shelter similar species in both seasons. This study presents findings on one of the first citywide gradients of urbanization density from the urban Neotropics, showing both differences and similarities in relation to previous studies from the Global North. Briefly, our species richness results showed a punctuated decrease when considering both seasons and years, rather than a gradual decrease or humped-shaped relations with higher richness at intermediately urbanized sites. Also, our composition findings stress the high representation of insectivore birds as part of avian communities across a citywide gradient of urbanization density. Undoubtedly, identifying the similarities and differences in the urban ecology patterns across cities, together with the particularities some urban systems, will allow for increased effectiveness of urban management and planning strategies in the transformation toward more livable, resilient, and biodiverse cities.

Avian Community Response to Short-rotation Aspen Forest Management

Abstract In the upper midwestern US and parts of Canada, forests dominated by Populus tremuloides (Aspen) are increasingly being considered as a bioenergy feedstock for power plants. When used for bioenergy, these forests are harvested at much younger ages than when they are used for more traditional products, such as pulpwood and lumber. To better understand the potential consequences of a shift in shorter-rotation-harvest strategies on avian communities, we employed point counts to examine bird community composition in a chronosequence (10-45 y since harvest) of 12 coppiced, even-aged Aspen stands. Young (8-15 y old), middle (20-44 y old), and mature (45 y old) stands had no significant differences in species richness or relative abundance, but distinct avian community assemblages were associated with each stand-age class. Four bird species were significantly associated with a particular age class. Maintaining a wide range of Aspen stand-age classes in the landscape appears to be the best strategy for c...

Avian community response to understory protection harvesting in the boreal forest of Alberta, Canada

Traditional harvesting in western boreal forests seeks to approximate natural disturbances, such as wildfire. In mixedwood forests, understory conifers such as white spruce are typically destroyed during natural disturbance harvest (NDH). Understory protection (UP) is a harvesting approach that seeks to protect understory conifers during hardwood harvesting in mixedwood forests. While understory protection harvesting has been implemented for over a decade in Alberta, Canada, there has been no assessment of its use by birds. We surveyed birds in UP and NDH harvest blocks, and the nearby unharvested forest, and evaluated differences in species richness and community composition between the three treatment types. We found NDH had significantly higher species richness than unharvested forests, but did not differ from UP. The three treatments all had significantly different avian community compositions, and NDH showed no convergence with the unharvested forest over 15-years post-harvest. However, UP represented an intermediary between NDH and unharvested forests. When comparing the oldest age class of UP with unharvested forest, we found no significant difference in the bird communities 12 years post-harvest. These results suggest that following understory protection harvest, the retained forest regenerates quickly, rapidly providing habitat to more mature forest species than NDH.

Habitat heterogeneity facilitates resilience of diurnal raptor communities to hurricane disturbance

The response of avian communities to hurricane disturbance may differ according to their specific requirements or functional groups, but little is known regarding the response of top-predator birds of prey to these disturbances. We aimed to evaluate the influence of the major Hurricane Patricia on the diversity of diurnal raptors in tropical dry forest, along the coast of Jalisco, Mexico. We conducted raptor surveys at 13 sites located within the eyewall radius of maximum hurricane winds along the path of the hurricane, and 16 sites located outside the hurricane eyewall. We compared the density and species richness of raptors among four habitats of tropical deciduous and semi-deciduous forest, mangroves, and agricultural fields, within the hurricane eyewall and outside the radius of maximum winds. Our results demonstrated a reduction in raptor density in tropical forests within the radius of maximum hurricane winds, where raptor density was significantly lower in deciduous forests within the hurricane eyewall compared to deciduous forests outside the eyewall. Species richness of diurnal raptors was similar among habitats and conditions with the exception that mangroves within the hurricane eyewall had significant higher raptor species richness compared to mangroves outside the eyewall. There was also a significant increase in species evenness, and decrease in similarity, of raptor communities in mangroves and deciduous forest sites within the hurricane eyewall compared to sites outside the eyewall. The reduced density of diurnal raptors in tropical forest sites within the path of the hurricane probably reflects the impact of hurricane winds on forest structure, whereas the increase in species richness and evenness of raptor communities in mangroves within the hurricane eyewall suggests that these habitats could provide a refuge for diurnal raptors following hurricane disturbance. Our results highlight the importance of maintaining landscape heterogeneity of native vegetation to provide alternate habitats for wildlife communities following major disturbance, and facilitate their resilience to extreme climatic events such as hurricanes.

Breeding Bird Community Continues to Colonize Riparian Buffers Ten Years after Harvest.

Riparian ecosystems integrate aquatic and terrestrial communities and often contain unique assemblages of flora and fauna. Retention of forested buffers along riparian habitats is a commonly employed practice to reduce potential negative effects of land use on aquatic systems. However, very few studies have examined long-term population and community responses to buffers, leading to considerable uncertainty about effectiveness of this practice for achieving conservation and management outcomes. We examined short- (1–2 years) and long-term (~10 years) avian community responses (occupancy and abundance) to riparian buffer prescriptions to clearcut logging silvicultural practices in the Pacific Northwest USA. We used a Before-After-Control-Impact experimental approach and temporally replicated point counts analyzed within a Bayesian framework. Our experimental design consisted of forested control sites with no harvest, sites with relatively narrow (~13m) forested buffers on each side of the stream, and sites with wider (~30m) and more variable width unharvested buffer. Buffer treatments exhibited a 31–44% increase in mean species richness in the post-harvest years, a pattern most evident 10 years post-harvest. Post-harvest, species turnover was much higher on both treatments (63–74%) relative to the controls (29%). We did not find evidence of local extinction for any species but found strong evidence (no overlap in 95% credible intervals) for an increase in site occupancy on both Narrow (short-term: 7%; long-term 29%) and Wide buffers (short-term: 21%; long-term 93%) relative to controls after harvest. We did not find a treatment effect on total avian abundance. When assessing relationships between buffer width and site level abundance of four riparian specialists, we did not find strong evidence of reduced abundance in Narrow or Wide buffers. Silviculture regulations in this region dictate average buffer widths on small and large permanent streams that range from ~22–25 m. Guidelines for this region are within the range of buffers included in our study, in which we observed no evidence for avian species loss or for a decline in species abundance (including riparian associated species).

English

Abstract. Surface mining transforms landscapes and ecosystem functions through the removal of vegetation and soil. Losses of vegetation correlate with declines, displacement, and transformations of songbird communities. Mine reclamation is a legislative requirement that can influence wildlife communities. The purpose of this study was to examine the avian community responses to mine reclamation practices and, as a proxy, assess the potential benefits and limitations of current reclamation approaches. Avian point counts were carried out at 202 plots on mined and surrounding non-mined areas throughout the Shale Hills Region of Alabama. These mines were reclaimed across a 26 year time-frame and using a variety of reclamation techniques. Six of the thirty-six bird species observed in high enough densities for detailed analysis showed differences of interest between reclaimed and random non-mined sites. Two species showed negative density responses: Carolina Chickadees (Poecile carolinensis), Hooded Warblers (Setophaga citrina). Conversely, densities of Field Sparrows (Spizella pusilla), Gray Catbirds (Dumetella carolinensis), Pine Warblers (Setophaga pinus), and Prairie Warblers (Setophaga discolor) responded positively to mine reclamation. We found that most mine reclamation in the Shale Hills Region of Alabama tended to shift habitat towards open canopy, edge, and grassland habitats. Though our study area tended to have fairly open forest structures (average basal areas around 13 m 2 /ha and average canopy closures around 50%), species that responded negatively were often associated with older sites with more closed canopies. Reclamation techniques should incorporate diverse canopy vegetation and thick mid-story cover to promote more complex vertical forest structure.

Avian community responses to post‐fire forest structure: implications for fire management in mixed conifer forests

AbstractFire is a natural process and the dominant disturbance shaping plant and animal communities in many coniferous forests of the western US. Given that fire size and severity are predicted to increase in the future, it has become increasingly important to understand how wildlife responds to fire and post‐fire management. The Angora Fire burned 1243 hectares of mixed conifer forest in South Lake Tahoe, California. We conducted avian point counts for the first 3 years following the fire in burned and unburned areas to investigate which habitat characteristics are most important for re‐establishing or maintaining the native avian community in post‐fire landscapes. We used a multi‐species occurrence model to estimate how avian species are influenced by the density of live and dead trees and shrub cover. While accounting for variations in the detectability of species, our approach estimated the occurrence probabilities of all species detected including those that were rare or observed infrequently. Although all species encountered in this study were detected in burned areas, species‐specific modeling results predicted that some species were strongly associated with specific post‐fire conditions, such as a high density of dead trees, open‐canopy conditions or high levels of shrub cover that occur at particular burn severities or at a particular time following fire. These results indicate that prescribed fire or managed wildfire which burns at low to moderate severity without at least some high‐severity effects is both unlikely to result in the species assemblages that are unique to post‐fire areas or to provide habitat for burn specialists. Additionally, the probability of occurrence for many species was associated with high levels of standing dead trees indicating that intensive post‐fire harvest of these structures could negatively impact habitat of a considerable proportion of the avian community.

Long‐term avian community response to housing development at the boundary of US protected areas: effect size increases with time

Summary Biodiversity conservation is a primary function of protected areas. However, protected areas also attract people, and therefore, land use has intensified at the boundaries of these lands globally. In the USA, since the 1970s, housing growth at the boundaries (<1 km) of protected areas has increased at a rate far higher than on more distant private lands. Here, we designed our analyses to address our central hypothesis that increasing housing density in and near protected areas will increasingly alter their avian communities. We quantified the relationship between abundance and richness of protected‐area avian species of greatest conservation need, land‐cover affiliates (e.g. species associated with natural land cover such as forest breeders) and synanthropes (e.g. species associated with humans) with housing density on the boundary of protected areas and on more distant private lands from 1970 to 2010 in three ecoregions of the USA. We accomplished this using linear mixed‐model analyses, data from the US Census Bureau and 90 routes of the North American Breeding Bird Survey. Housing density at the boundary of protected areas tended to be strongly negatively related with the abundance and richness of species of greatest conservation need and land‐cover affiliates (upwards of 88% of variance explained) and strongly positively related with synanthropes (upwards of 83% of variance explained). The effect size of these relationships increased in most cases from 1970 to 2010 and was greatest in the densely developed eastern forests. In the more sparsely populated West, we found similar, though weaker, associations. Housing density on private lands more distant from protected areas had similar, but more muted negative effects. Synthesis and applications. Our results illustrate that as housing density has increased along the boundary of protected areas, the conservation benefit of these lands has likely diminished. We urge conservation planners to prioritize the purchase of private‐land inholdings in order to maximize the extent of unfragmented natural lands within protected areas. Further, we strongly recommend that land‐use planners implement boundary management strategies to alter the pattern of human access to protected areas, cluster development to concentrate the footprint of rural housing, and establish conservation agreements through local land trusts to buffer protected areas from the effects of development along protected‐area boundaries. To maximize the conservation benefit of protected areas, we suggest that housing development should be restricted within 1 km of their boundaries.

The causal response of avian communities to suburban development: a quasi-experimental, longitudinal study

Correlations between urbanization and biodiversity are well known, but the causes driving such associations are lacking. We used a long-term, quasi-experimental approach to study the responses of avian communities to suburban and exurban development around Seattle, WA, USA. We measured indices of bird abundance, reproduction, and survival for 12 years at many locations, including 5 forest ‘reserves,’ 10 existing ‘developments,’ and 11 ‘changing’ sites where ongoing development converted forests to single-family residential neighborhoods. In the first few years of clearing, building, and occupation of new neighborhoods by humans avian communities shifted from those typical of second-growth forest to those more characteristic of developments. During this time avian diversity increased and numerical dominance by abundant birds declined. Species that adapted and exploited development reproduced more successfully there than did forest-dependent species that avoided development. Adults of species that thrived in developments attained equal annual survival across reserved to developed landscapes, while species that avoided neighborhoods tended to survive poorly outside of reserves. The humans living in our study areas frequently fed birds and provided nest boxes. These actions were positively correlated with increases in secondary cavity nesting and seed eating birds. Humans also maintained outdoor cats and 11 % of humans both fed birds and let their cats outside. These actions were negatively correlated with the abundance of birds regularly using feeders. We suggest that a key management goal in urban ecosystems is the maintenance of avian diversity because a diverse avifauna engages a diversity of humans.

Two-sided edge responses of avian communities in an urban landscape

Impacts of habitat edges on wildlife populations have received considerable attention, yet few researchers have quantified changes in animal community structure on both sides of an interface between distinct habitats. To gain a better understanding of the ways in which species-specific responses scale up to produce community patterns across habitat boundaries, we examined the response of avian communities to forest-suburb edges in northeastern Illinois, USA. We surveyed bird assemblages using replicated point-transects (n = 21) that crossed boundaries between remnant forest patches and suburban residential areas in order to compare differences in community composition, species distributions, and densities. Forest and suburban bird communities were distinct, and community composition changed with distance-from-edge in forests but not suburbs. Abundances of many species that were common in the forest increased with distance-from-edge in the forest, whereas numbers of common species in the suburbs were largely unaffected by distance-from-edge. Using a new metric that we termed “tolerance,” we found many forest species avoided the edge and suburbs, and suburban species were present near the edge but did not venture far into forest. Overall, distance to the forest-suburb boundary was more influential in structuring avian communities in the forest. Some species of conservation concern crossed edges into the suburbs, suggesting that management activities may improve suburban biodiversity. Many other imperiled forest species, however, will only be retained in urban environments through the protection of forest interior habitat.

Response of avian communities to invasive vegetation in urban forest fragments

ABSTRACT Proliferation of invasive plants in forest understories throughout North America has prompted restoration efforts focused on removal of invasive vegetation. Although the negative impacts of invasives on native plant communities are well documented, effects on forest bird communities remain largely unknown. To address this issue, we examined the response of avian communities to invasive plants in forest fragments across 4 counties in northeastern Illinois, a region characterized by extensive urbanization. We surveyed breeding bird communities in 46 forest plots representing a gradient in abundance of invasive woody plants. We quantified vegetation structure and composition within plots, as well as landscape context. Exotic trees and shrubs were present on all but 3 plots. Although native trees were common, native species represented <7% of total stem density of shrubs. Measures of invasion were weakly correlated with those representing urbanization, yet broad-scale measures of urbanization such as...

Avian community responses to variability in river hydrology.

River flow is a major driver of morphological structure and community dynamics in riverine-floodplain ecosystems. Flow influences in-stream communities through changes in water velocity, depth, temperature, turbidity and nutrient fluxes, and perturbations in the organisation of lower trophic levels are cascaded through the food web, resulting in shifts in food availability for consumer species. River birds are sensitive to spatial and phenological mismatches with aquatic prey following flow disturbances; however, the role of flow as a determinant of riparian ecological structure remains poorly known. This knowledge is crucial to help to predict if, and how, riparian communities will be influenced by climate-induced changes in river flow characterised by more extreme high (i.e. flood) and/or low (i.e. drought) flow events. Here, we combine national-scale datasets of river bird surveys and river flow archives to understand how hydrological disturbance has affected the distribution of riparian species at higher trophic levels. Data were analysed for 71 river locations using a Generalized Additive Model framework and a model averaging procedure. Species had complex but biologically interpretable associations with hydrological indices, with species’ responses consistent with their ecology, indicating that hydrological-disturbance has implications for higher trophic levels in riparian food webs. Our quantitative analysis of river flow-bird relationships demonstrates the potential vulnerability of riparian species to the impacts of changing flow variability and represents an important contribution in helping to understand how bird communities might respond to a climate change-induced increase in the intensity of floods and droughts. Moreover, the success in relating parameters of river flow variability to species’ distributions highlights the need to include river flow data in climate change impact models of species’ distributions.

Avian community responses to restoration efforts in a complex volcanic landscape

Monitoring of restoration efforts has focused primarily on the effects of restoration activities for the vegetation component of ecosystems, but restoration efforts should consider other wildlife groups to fully assess ecosystems recovery. We assessed differences in avian community responses among managed (restoration and reforestation sites), disturbed (abandoned cropfields and volcanic ash deposits), and natural (undisturbed and late-seral forests) habitats within a volcanic landscape with a complex disturbance history. Our results indicate that bird communities vary among managed habitats, as a consequence of both their disturbance history and current management strategy. Data indicate that restoration activities promote more diverse, even, and heterogeneous (both taxonomic and functional) bird communities that resemble those of natural habitats. Although we found that reforestation activities could enhance diversity and evenness of bird communities, planting only tree species as a management strategy might not be sufficient to achieve bird communities similar to those of natural habitats. Thus, we encourage restoration efforts, even in productive ecosystems, to enhance the effectiveness of biodiversity recovery. Based on our results, we highlight the importance of defining particular restoration strategies for each site, as local disturbance histories and site-specific characteristics could produce particular responses in bird communities, despite the presence of rich species pools in adjacent forests. We conclude that understory complexity is an important factor to consider in restoration programs that include wildlife components in their goals.