Total Bird Abundance Research Articles

Avian Responses to Different Grazing Management Practices in Neotropical Temperate Grasslands: A Meta-Analysis

Bird populations inhabiting the Rio de la Plata Grasslands in southern Brazil, Argentina, and Uruguay are known to be affected by livestock grazing practices. Cattle grazing can lead to changes in bird assemblages by affecting the heterogeneity of vegetation structures. We conducted a meta-analysis using studies that reported bird richness and abundance under different grazing management practices. We compared ranches under continuous grazing management (control, CGM) to (1) ranches under technological inputs management (TIM, herbicides and exotic pastures) and (2) ranches under ecological process-based management (EPM), which include ranches that utilise controlled and rotational grazing. We used random effects multilevel linear models to evaluate grazing regimen impacts. Our results indicate a negative impact of TIM on both bird abundance and richness (mean ± SE: −0.25 ± 0.07 and −0.92 ± 0.10, respectively) since the use of inputs simplifies vegetation structure and results in the loss of ecological niches. Compared to CGM, the influence of EPM on total bird abundance appears to be more dependent on grassland height, as evidenced by a decline in short grasses and increase in tall grasses. Our meta-analysis suggests that EPM practices may be beneficial for the conservation of endangered tall-grass birds.

Space-for-time substitutions exaggerate urban bird-habitat ecological relationships.

North American bird abundance has declined by 29% over the last 50 years. These continental population dynamics interact with local landscape changes to affect local bird diversity. Mitigating local declines in cities is particularly significant because (a) such declines greatly impact human-bird relationships since most people live in cities and (b) cities provide levers to create bird-friendly habitat, such as managing yards and gardens, street trees, and urban parks. Yet, the potential for cities to modify habitats to mitigate broader bird declines remains unclear. Studies have been stymied by the difficulty of assembling mutidecadal habitat-bird population datasets. Instead, studies have substituted space for time (e.g. used habitat associations across space at one time point to project future species abundance due to changing land use), but this method may fail amidst nonstationary environments of the Anthropocene. Here, we test the validity of space-for-time substitutions for explaining changes in bird abundance in a North American city over the past two decades by examining the degree to which these changes are explainable by changes in local landcover at multiple spatial scales. Specifically, we use longitudinal urban bird surveys of Metro Vancouver, BC, Canada from 1997 and 2020; deep learning models of remote sensing data to classify contemporaneous landcover; out-of-sample prediction and boosted regression trees to identify multiple spatial scales of landcover that best explained bird abundance (i.e. optimal scale of effect for each species by each habitat); and Bayesian multispecies abundance models in Stan to determine relationships between changes in landcover and bird abundance. We found that total bird abundance declined by 26% over the last two decades. Landcover measured at both 50 m and optimal scales explained spatial variation in bird abundance, but only landcover at the optimal scale explained temporal changes, and only partially. These results suggest that space-for-time substitutions overemphasize habitat-bird ecological relationships, urban habitats only partially determine bird abundance, and measuring habitat at the appropriate scale is important for capturing the most relevant changes in landscapes.

Microhabitat coverage influences avian species composition more than habitat heterogeneity in Hong Kong urban parks

The relationship between habitat heterogeneity and diversity can underpin design of urban spaces for biodiversity conservation. The area-heterogeneity trade-off hypothesis predicts that higher habitat heterogeneity should result in an increase in species richness but only up to a point, beyond which habitat micro-fragmentation leads to decreases in species diversity. However, the strength of area-heterogeneity trade-offs at small spatial scales is not well studied. We studied the relationship between avian diversity and habitat heterogeneity in 16 small urban parks across Hong Kong during the winter dry season across 2016 and 2017 (ten repeated surveys in total for each park). Habitat heterogeneity was assessed by measuring the evenness of microhabitat coverage of seven habitats as well as vertical canopy cover. In total, 12,973 individuals of 73 bird species were recorded in the study. Habitat heterogeneity had a small but negligible effect on total bird species richness or abundance. However, water coverage was positively related to total, intermediately rare and habitat specialist bird species richness, and shrub coverage was positively related to total and common bird species richness. These results demonstrate that environmental heterogeneity had little effect on avian species richness in urban green spaces at small spatial scales. We also found that microhabitat coverage can affect avian diversity and abundance, and these effects are specific to certain groups of bird species. When managing urban green spaces for biodiversity conservation in densely urbanized cities, a decrease in management disturbance (e.g. tree topping or pesticide application) will likely benefit avian species. Together with the fact that some locally uncommon species were observed throughout the study, capacity exists for environmental enhancement of these small urban parks to contribute to local avian conservation.

Bird Community Responses to Restoration along Las Vegas Wash, Nevada

In a 12-year study of seasonal bird use along Las Vegas Wash (Clark County, Nevada), an area undergoing intensive channel stabilization and riparian and wetland restoration, we found that total bird abundance and species richness significantly increased. In the late phase of the project, total bird abundance was greatest during the nonbreeding season and winter transition, and species richness was greatest during the fall transition. Species associated with riparian shrubs decreased, likely as a response to large-scale removal of non-native shrubs and the lag in recovery of a native shrub understory. Species associated with trees and the mid-story had a mixed response, with detections of those species previously most closely associated with non-native trees showing a negative trend, while those associated with native overstory plants showing an increasing or mixed trend. Detections of wetland and aquatic species increased significantly throughout the project. This study shows differential restoration responses of species based on their natural history, seasons of primary use of the site, and the lag time in recovery of particular vegetation elements that are used by various species assemblages.

Upland vegetation removal as a potential tool for facilitating landward salt marsh migration

To increase the resilience of salt marshes subject to sea‐level rise impacts, managers can focus on interventions within current marsh footprints or in adjacent uplands to facilitate landward marsh migration. The latter approach may be more appropriate when degradation is severe and in situ intervention options are limited. Strategies for facilitating marsh migration include removing artificial barriers, soil grading to reduce steep topography, and manipulating adjacent upland vegetation that can hinder migration, but experiments testing the effectiveness of these activities are limited. We therefore conducted a field experiment to determine if physically removing three upland vegetation types (forest, shrub, and Phragmites australis) adjacent to a Rhode Island salt marsh facilitates short‐term marsh migration. Upland vegetation removal led to increased ambient light in all habitats, significantly enhanced marsh plant cover, extent, and elevation in shrub habitat, and declines in total bird abundance in forest and shrub habitats. Enhanced migration did not occur in forest or Phragmites habitats, and in shrubs, marsh plants only colonized where Baccharis halimifolia, common in upper marsh borders, had been removed. Five years after removal, all upland habitats and associated vegetation were indistinguishable from initial conditions. Our study suggests that upland plant removal might provide a limited window for facilitating salt marsh migration and that more intensive methods may be needed for sustained, longer‐term benefits. It also demonstrates that there may be ecological trade‐offs to consider when altering upland habitats to enhance landward marsh migration.

BIRD COMMUNITIES RESPOND TO THE SEASONAL FRUIT AND FLOWER AVAILABILITY IN A FRAGMENTED TROPICAL ANDEAN LANDSCAPE

Fire is one of the main causes of fragmentation in tropical Andean forests. Fragmentation can influence plant reproductive phenology, which in turn affects bird communities. In the Bolivian Yungas, we investigated how the seasonal availability of fruits and flowers affects bird richness, abundance and bird community composition in forest edges and adjacent bracken (Pteridium ferns) dominated areas. We captured birds with mist nets at eight sites during the dry, transition and wet seasons, and recorded fruit and flower availability through phenological observations and plant collections. We examined variation in species richness and abundance using generalized linear mixed-effects models, and bird species composition in each season using multivariate analyses. Fruit availability was higher in the transition and wet seasons, and lowest in the dry season, while flower availability did not differ among seasons. Bird species richness and abundance were significantly higher in bracken areas, although there was significantly lower fruit availability than at the forest edge, and these were mainly generalist bird species that may be tolerant to disturbance. Total bird abundance increased with higher fruit availability in both habitats, and with flower availability at the forest edge. Bird species composition differed between forest edges and bracken areas in the transition and the wet seasons, being influenced by fruiting and flowering phenology in the dry and transition seasons, and elevation in all seasons. Our results show the varying seasonal influence of plant reproductive phenology on avian communities of disturbed habitats, although other large scale factors associated with fragmentation may also shape bird communities.

Old-growth forests are critical to safeguard tropical birds in complex landscape mosaics exposed to slash-and-burn agriculture

ContextSlash-and-burn agriculture generates landscape mosaics composed of different land uses. Ecological theory postulates that in these mosaics, the structure of species assemblages depends on both local- and landscape-scale factors, but their relative role remains poorly known.ObjectivesUnderstanding the relative importance of local and landscape variables for bird assemblages in landscape mosaics of the Mayan tropical forest, Mexico.MethodsWe evaluated the effect of two local variables (land use type and tree basal area) and two landscape variables (old-growth forest cover and human proximity) on bird abundance and diversity, separately assessing forest and non-forest birds. As species extirpation may accelerate when forest loss exceeds certain limits (extinction thresholds), we assessed forest loss effects with linear and nonlinear models.ResultsWe recorded 1867 birds from 118 species in four land-use types (old-growth forest, secondary forest, burned lands, and agricultural lands). Land-use type and surrounding old-growth forest cover better predicted bird abundance and diversity than tree basal area and human proximity. Agricultural lands showed the lowest abundance and diversity of forest species, but the highest abundance and diversity of non-forest species. We found no support for the extinction threshold hypothesis. Yet, independently of the land use, old-growth forest loss decreased the diversity of forest species and increased the abundance and diversity of non-forest species. Human proximity also decreased total bird abundance, especially because of the loss of forest species.ConclusionsOur findings highlight the key role played by old-growth forests for preserving bird assemblages in landscape mosaics exposed to slash-and-burn agriculture.

Redistribution of songbirds within a migratory stopover site as a response to sylviid warbler song playback

Assessing habitat quality is critical for migrating birds, with implications for fuel loading, predation risk and timing of departure. To efficiently distribute within stopover sites, migrants rely on various cues that facilitate habitat quality assessment. In this study, we conducted a playback experiment at a mid‐route stopover site to test the effects of vocal cues, specifically bird songs, on habitat redistribution during spring migration. To estimate the effect of bird songs on bird abundance we mist‐netted and ringed birds for 60 days on alternating playback treatment (playing songs of three sylviid warbler species) and no playback (control) days. A nearby site was used to control for fluctuations caused by migration waves. Overall, total bird abundance was significantly increased by the playback treatment. This increase resulted from the attraction of conspecifics (species whose songs were played) rather than of other species – sylviids or others. Correspondingly, species richness was seemingly unaffected. To investigate the relationship between internal‐state factors and the attraction to playback in the most abundantly attracted species, Eurasian Blackcap Sylvia atricapilla, we tested associations with age, sex and body condition index but found no significant effects, possibly because of the limited sample size. Our findings challenge established ideas regarding heterospecific attraction and contradict previous studies. Attraction to bird song is discussed in the context of geographical location, timing and internal drivers. Vocal cues, specifically bird songs, may affect micro‐habitat selection by migrating songbirds during stopovers. Consequently, we call for consideration of the influence of the acoustic environment on birds during migratory stopover in future studies, habitat management and conservation efforts.

Impacts of noise pollution from high-speed rail and road on bird diversity: a case study in a protected area of Italy

The disturbance of infrastructures may affect biological communities that are exposed to them. This study assesses the impact of high-speed (highway and railway) infrastructures in a protected study site, the Natural Reserve Fontanili di Corte Valle Re (Emilia–Romagna, Italy). We compared bird diversity with sound intensity and frequency in three sampling areas, increasingly distant from the infrastructures at the border with the reserve, during the last 4 years (2019–2022), monitoring sedentary, nesting, and migratory bird species. We hypothesize a decreasing diversity closer to the source of disturbance, which is mostly attributable to noise pollution. Our findings confirmed this trend, and we show that, in particular, disturbance seems to influence species richness more than the total abundance of birds. We also discovered that highway disturbance was much higher than railway in terms of frequency and duration. In light of these results, we suggest that some species, which have a behavioral ecology strongly based on singing to communicate with each other for their reproductive and defensive strategies, may suffer more from constant acoustic disturbance. The installation of effective noise barriers to shield the sound produced by the highways should be considered a mandatory request not only in proximity to houses but also in the vicinity of protected areas.

Tall, large-diameter trees and dense shrub layer as key determinants of the abundance and composition of bird communities in oak-dominated forests

Increasing human activity is altering the structure of forests, which affects the composition of communities, including birds. However, little is known about the key forest structure variables that determine the richness of bird communities in European temperate oak forests. We, therefore, aimed to identify key variables in these habitats that could contribute to the design of management strategies for forest conservation by surveying 11 oak-dominated forest sites throughout the mid-mountain range of Hungary at 86 survey points to reveal the role of different compositional and structural variables for forest stands that influence the breeding bird assemblages in the forests at the functional group and individual species levels. Based on decision tree modelling, our results showed that the density of trees larger than 30 cm DBH was an overall important variable, indicating that large-diameter trees were essential to provide diverse bird communities. The total abundance of birds, the foliage-gleaners, primary and secondary cavity nesters, residents, and five specific bird species were related to the density of high trunk diameter trees. The abundance of shrub nesters was negatively influenced by a high density of trees over 10 cm DBH. The density of the shrub layer positively affected total bird abundance and the abundance of foliage gleaners, secondary cavity nesters and residents. Analysis of the co-dominant tree species showed that the presence of linden, beech, and hornbeam was important in influencing the abundance of various bird species, e.g., Eurasian Treecreeper (Certhia familiaris), Marsh Tit (Poecile palustris) and Wood Warbler (Phylloscopus sibilatrix). Our results indicated that large trees, high tree diversity, and dense shrub layer were essential for forest bird communities and are critical targets for protection to maintain diverse and abundant bird communities in oak-dominated forest habitats.

Fire responses by bird guilds and species in heathy dry forests in central Victoria, Australia

Predicted increases in fire frequency and extent are being realised across Australia, bringing changes to the fire regime which may influence the availability of essential resources required by birds. However, few studies have examined either the impacts of fire frequency on birds or the impacts from both wildfire and planned burns, combined. Birds were surveyed eight times across 84 sites in heathy dry forests in central Victoria, south-east Australia, from 2012 to 2014. Fire history records were retrieved from the 1970’s onwards, the time from which accurate planned burn records were kept. We developed mixed models to investigate how birds responded to time-since-fire and fire frequency, analysing total bird abundance, ten foraging guilds and 30 individual species. We found distinct responses by all modelled guilds and species to time-since-fire, along with evidence for responses to fire frequency. The greatest shifts in species’ abundances occurred during the first ten years post fire, with bird species commonly present across the stages greater than ten years since fire. For total bird abundance there was no statistically detectible difference between recently burnt forest (0-6 months) and other age classes. However, some guilds showed a significant drop in abundance in newly burnt vegetation (e.g. bark foragers, damp ground insectivores, those that feed on seeds close to the ground, tall shrub foragers). It is with guild and species’ responses that more differences across vegetation age classes became apparent. Significant increases in abundance were apparent in both the regrowth and new growth vegetation age classes, compared with older habitat (e.g. canopy foragers, damp ground insectivores, tall shrub foragers); open ground foragers were especially common in post-fire regrowth but then significantly declined. Other responses were more complex, with species’ preferences reflecting their foraging ecology. Some birds showed preferences across two age classes: sites that were young post-fire regrowth (6 months–2.5 years since fire) along with sites of old habitat (>35 years since fire), (e.g. Crimson Rosella, Scarlet Robin, Sulphur-crested Cockatoo), while some ground-foraging species became scarce in dense new-growth vegetation that appears 2.5–10 years post fire (e.g. Australian Magpie, Laughing Kookaburra and White-winged Chough). Such species may deserve specific management strategies to maintain populations in forests where substantial areas are burnt by wildfire or planned burns, over short periods of time. The model for total bird abundance showed a significant fire frequency response with birds preferring sites twice burnt within 35 years (e.g. bark and canopy-foraging guilds). Four guilds demonstrated a preference for sites frequently burnt, increasing in abundance as number of burns increased (nectarivores, open-ground foragers, seeds in trees foragers, tall shrub foragers). In contrast, two species appeared to prefer sites that had experienced low fire frequencies, a response not common to their guilds. Laughing Kookaburra (carnivore) and White-winged Chough (forages on open ground among trees) generally declined in abundance with increasing fire frequency.

Effects of Dutch agri-environmental field margins and bird plots on cropland birds

Agri-environmental measures (AEMs) are the main instrument of the Common Agricultural Policy to protect farmland biodiversity, but their effectiveness is questioned. In the Netherlands, AEMs have been implemented by farmers’ collectives since 2016, with the goal to improve the spatial targeting and coordination of measures, and thereby increase their effectiveness. The objective of this paper is to assess the effects of two AEMs, bird plots and field margins, on the abundance of seven cropland bird species targeted by the Dutch agri-environmental policy, and on their total abundance and species richness. The study was carried out in four farmers’ collectives in the provinces of Groningen, Drenthe and Flevoland in the Netherlands. We assessed how bird abundance and species richness measured on AEM plots and control plots were related to management and landscape factors. Furthermore, we assessed whether bird abundance and species richness measured on AEM plots were related to the spatial concentration of other AEM plots in landscapes surrounding AEM plots. With regard to plot management, we found a significant positive effect of field margins on skylarks, yellowhammers, common linnets, common kestrels, total bird abundance and species richness. Bird plots had a significant positive effect on skylarks and total bird abundance. However, western yellow wagtails, northern lapwings and Eurasian oystercatchers did not benefit from the two studied measures, likely because the vegetation in the bird plots and field margins is too high and dense for these species. Landscape factors, such as landscape openness, had contrasting effects on the analysed species, due to their different habitat requirements. Hence, there are no optimal landscapes for all target species, which underlines the need for a fine scale spatial targeting of measures based on species habitat requirements. Furthermore, the spatial concentration of other AEM plots in the landscape surrounding AEM plots had a significant effect for only two species (yellowhammer and western yellow wagtail), and this effect was negative. Thus, our results suggest that - for the studied species and landscapes - the type of measures and landscape in which they are taken are more important than their spatial concentration.

Sharing land via keystone structure: Retaining naturally regenerated trees may efficiently benefit birds in plantations.

Meeting food/wood demands with increasing human population and per-capita consumption is a pressing conservation issue, and is often framed as a choice between land sparing and land sharing. Although most empirical studies comparing the efficacy of land sparing and sharing supported land sparing, land sharing may be more efficient if its performance is tested by rigorous experimental design and habitat structures providing crucial resources for various species-keystone structures-are clearly involved. We launched a manipulative experiment to retain naturally regenerated broad-leaved trees when harvesting conifer plantations in central Hokkaido, northern Japan. We surveyed birds in harvested treatments, unharvested plantation controls, and natural forest references 1-year before the harvest and for three consecutive postharvest years. We developed a hierarchical community model separating abundance and space use (territorial proportion overlapping treatment plots) subject to imperfect detection to assess population consequences of retention harvesting. Application of the model to our data showed that retaining some broad-leaved trees increased the total abundance of forest birds over the harvest rotation cycle. Specifically, a preharvest survey showed that the amount of broad-leaved trees increased forest bird abundance in a concave manner (i.e., in the form of diminishing returns). After harvesting, a small amount of retained broad-leaved trees mitigated negative harvesting impacts on abundance, although retention harvesting reduced the space use. Nevertheless, positive retention effects on the postharvest bird density as the product of abundance and space use exhibited a concave form. Thus, small profit reductions were shown to yield large increases in forest bird abundance. The difference in bird abundance between clearcutting and low amounts of broad-leaved tree retention increased slightly from the first to second postharvesting years. We conclude that retaining a small amount of broad-leaved trees may be a cost-effective on-site conservation approach for the management of conifer plantations. The retention of 20-30 broad-leaved trees per ha may be sufficient to maintain higher forest bird abundance than clearcutting over the rotation cycle. Retention approaches can be incorporated into management systems using certification schemes and best management practices. Developing an awareness of the roles and values of naturally regenerated trees is needed to diversify plantations.

Breeding bird abundance and species diversity greatest in high-severity wildfire patches in central hardwood forests

In 2016, mixed-severity wildfires in the southern Appalachians created a gradient of forest structures not typical following prescribed burns, providing a unique opportunity to study temporally dynamic conditions and breeding bird response. We measured forest structure and breeding bird communities across a fire-severity gradient in 3 burned and 3 unburned watersheds for 5 years (Y1-Y5). We categorized plots as unburned (NB), low- (L), moderate- (M), or high-severity (H) using a composite fire-severity index. Tree mortality increased with fire-severity category (FSC) and over time; by Y5, 7 % of trees in NB, 11 % in L, 38 % in M, and 71 % in H had died. Shrub recovery was rapid and most pronounced in H, exceeding other FSCs (70 % vs 21 %–44 %) by Y5. Total bird abundance, species richness, and diversity increased over time in H (by Y3) and M (by Y4); by Y5, these metrics were highest in H and twice as high in H as in NB. Low-severity wildfires had no detectable effects on birds. Abundance of 7 species was greatest in higher-severity FSCs; 11 species did not differ among FSC, although ovenbirds (Seiurus aurocapilla) indicated a trend of lower abundance in H. No species was limited to NB, L, or M, whereas disturbance-dependent indigo bunting (Passerina cyanea), chestnut-sided warbler (Setophaga pensylvanica), and eastern towhee (Pipilo erythrophthalmus) were primarily associated with H. Increased richness and diversity were associated with heavy tree mortality and subsequent shrub recovery in H, accompanied by an influx of disturbance-dependent species and positive or neutral responses by most other species. Results highlight the interrelated roles of fire severity and time in driving forest structure and breeding bird response. Breeding birds responded to high-severity burns similarly to silvicultural treatments with heavy canopy reduction documented in other studies, offering possible alternatives when managing for breeding bird diversity in hardwood forests.

Effects of Landscape Features on Bird Community in Winter Urban Parks.

Urban parks, as critical components of the urban green space, have practical significance in studying the influence of landscape characteristics on birds. Nine urban parks in Fuzhou, China, were used as study objects to explore the influence of landscape features (patch, landscape, and surrounding environment indices) on bird communities. The results showed that (1) from December 2021 to February 2022, we found a total of 2874 individuals belonging to 61 species of 9 orders, 32 families, which were dominated by the birds of Passeriformes (37 species of 24 families, accounting for 89.91% of the total number of individuals) and resident birds in Fuzhou urban parks (n = 30; 85.46%); (2) The park area, park perimeter, woodland area, grassland area, and the park shape index increased as the distance to the city center increases; (3) Bird diversity responds differently to different landscape features. The total abundance of birds, the abundance of winter migrant birds, and the richness of winter migrant birds increased with the park area. And the park shape index affects positively for the the α-diversity of birds and the abundance of resident birds. Woodland proportion and waterbody shape index affected positively on the richness and α-diversity of resident birds. To promote the diversity of regional birds, it is recommended that the construction and planning of urban parks should enlarge the park area as much as possible, increase the proportion of woodland, and make shorelines more irregular. Our study could serve as a reference for the construction of biodiversity enhancements in core green areas of urban parks.

A Spatial Modeling Framework for Monitoring Surveys with Different Sampling Protocols with a Case Study for Bird Abundance in Mid-Scandinavia

Quantifying the total number of individuals (abundance) of species is the basis for spatial ecology and biodiversity conservation. Abundance data are mostly collected through professional surveys as part of monitoring programs, often at a national level. These surveys rarely follow exactly the same sampling protocol in different countries, which represents a challenge for producing biogeographical abundance maps based on the transboundary information available covering more than one country. Moreover, not all species are properly covered by a single monitoring scheme, and countries typically collect abundance data for target species through different monitoring schemes. We present a new methodology to model total abundance by merging count data information from surveys with different sampling protocols. The proposed methods are used for data from national breeding bird monitoring programs in Norway and Sweden. Each census collects abundance data following two different sampling protocols in each country, i.e., these protocols provide data from four different sampling processes. The modeling framework assumes a common Gaussian Random Field shared by both the observed and true abundance with either a linear or a relaxed linear association between them. The models account for particularities of each sampling protocol by including terms that affect each observation process, i.e., accounting for differences in observation units and detectability. Bayesian inference is performed using the Integrated Nested Laplace Approximation (INLA) and the Stochastic Partial Differential Equation (SPDE) approach for spatial modeling. We also present the results of a simulation study based on the empirical census data from mid-Scandinavia to assess the performance of the models under model misspecification. Finally, maps of the expected abundance of birds in our study region in mid-Scandinavia are presented with uncertainty estimates. We found that the framework allows for consistent integration of data from surveys with different sampling protocols. Further, the simulation study showed that models with a relaxed linear specification are less sensitive to misspecification, compared to the model that assumes linear association between counts. Relaxed linear specifications of total bird abundance in mid-Scandinavia improved both goodness of fit and the predictive performance of the models.

Habitat provision is a major driver of native bird communities in restored urban forests.

Urbanization, and the drastic loss of habitat it entails, poses a major threat to global avian biodiversity. Ecological restoration of urban forests is therefore increasingly vital for native bird conservation, but control of invasive predators may also be needed to sustain native bird populations in cities where species invasions have been particularly severe.We evaluated restoration success by investigating changes in native bird communities along a restoration chronosequence of 25 restored urban forests representing 72 years of forest development, which we compared to two target reference systems and a control system. We hypothesized that total species richness and relative abundance of native forest birds would increase with the age of restoration planting. We further hypothesized that relative abundance of rats, possums and cats would negatively impact native birds, while amount of native forest in the surrounding landscape would have a positive effect.We used structural equation modelling (SEM) to investigate the relative influence of forest structure (complexity index, tree height, canopy openness, basal area, species richness and density), landscape attributes (patch area, perimeter length, landscape composition within three buffer zones, distance to the nearest road and water source) and invasive mammalian predator indices of relative abundance on total species richness and relative abundance of native forest birds.Species richness increased with age of restoration planting, with community composition progressing towards that found in target reference systems. SEM revealed that years restored was a direct driver of bird species richness but an indirect driver of abundance, which was directly driven by canopy openness. Contrary to our predictions, invasive mammals had no significant effect on native bird species richness or abundance.Our results demonstrate that provision and improvement of habitat quantity and quality through restoration is the vital first step to re‐establishing native forest bird communities in cities.

Single-row exclusion nets: an alternative pest control method with no detectable impact on breeding bird assemblages in orchards bordered by hedgerows

Agricultural intensification has led to dramatic declines in bird populations. In particular, the acknowledged role of synthetic pesticides on direct bird intoxication or food resource depletion urges us to seek alternative crop protection methods. Pest exclusion netting systems have recently gained popularity among fruit growers as an efficient means of reducing pest attacks, allowing their transition to organic farming. Single-row exclusion nets, which only cover fruit trees and leave uncovered both the inter-row grassy strips and the hedges, are increasingly being used in apple orchards of Southern Europe. However, net-induced effects on wildlife remain unknown. This study is the first to assess the impacts of single-row exclusion nets on breeding bird communities. We hypothesized that the exclusion net effects would be weaker than those associated with synthetic pesticide use, except for bird species that forage in the tree canopy. We monitored breeding bird abundance, and species richness in 46 commercial apple orchards managed using integrated pest management (IPM) or organic standards with or without exclusion nets. We counted 705 birds belonging to 32 different species. Total bird abundance, the number of observed species, and the Chao1 estimate of species richness were influenced by orchard management strategy. Breeding bird assemblages in organic orchards were as numerous and diverse in both the presence and absence of exclusion nets. In contrast, both bird abundance and species richness were significantly decreased in IPM orchards. The abundance and species richness of bird assemblages and the abundance of a few individual species also increased with the number of hedgerows bordering the orchards. Our results demonstrate that single-row netting systems for organic farming represent an effective pest control strategy with no significant impact on bird communities and highlight the importance of hedgerows along the orchards’ edges.

Titmice are a better indicator of bird density in Northern European than in Western European forests.

Population sizes of many birds are declining alarmingly and methods for estimating fluctuations in species’ abundances at a large spatial scale are needed. The possibility to derive indicators from the tendency of specific species to co‐occur with others has been overlooked. Here, we tested whether the abundance of resident titmice can act as a general ecological indicator of forest bird density in European forests. Titmice species are easily identifiable and have a wide distribution, which makes them potentially useful ecological indicators. Migratory birds often use information on the density of resident birds, such as titmice, as a cue for habitat selection. Thus, the density of residents may potentially affect community dynamics. We examined spatio‐temporal variation in titmouse abundance and total bird abundance, each measured as biomass, by using long‐term citizen science data on breeding forest birds in Finland and France. We analyzed the variation in observed forest bird density (excluding titmice) in relation to titmouse abundance. In Finland, forest bird density linearly increased with titmouse abundance. In France, forest bird density nonlinearly increased with titmouse abundance, the association weakening toward high titmouse abundance. We then analyzed whether the abundance (measured as biomass) of random species sets could predict forest bird density better than titmouse abundance. Random species sets outperformed titmice as an indicator of forest bird density only in 4.4% and 24.2% of the random draws, in Finland and France, respectively. Overall, the results suggest that titmice could act as an indicator of bird density in Northern European forest bird communities, encouraging the use of titmice observations by even less‐experienced observers in citizen science monitoring of general forest bird density.

Spatial Heterogeneity of Steppe Bird Community in the Azov-Black Sea Enclave of the European Dry-Steppe Zone (Southern Ukraine)

Over the period 2007–2019, the author’s censuses of steppe birds in the Azov-Black Sea dry-steppe enclave determined five species as dominants and co-dominants by their abundance. Thus, Melanocorypha calandra dominates throughout the whole area, Emberiza calandra dominates in 4 subregions and co-dominates in 5 subregions, Motacilla feldegg, Emberiza hortulana, Anthus campestris, Alauda arvensis dominate in 1 subregion and do not dominate or co-dominate in 1–4 subregions. There is a general increasing trend in the total abundance of steppe birds and the number of their rare breeding species from north-west to south-east, whereas the number of their dominants and co-dominants grows in the opposite direction. According to the list, the correlation between the dominants/co-dominants and the number of rare breeding steppe species, it was revealed that the most valuable for the support of the steppe bird populations are subregions with the largest areas of virgin steppes (the Kerch Peninsula, Western and Central Crimea). The least important are the subregions with the highest degree of anthropogenic transformation (northern part of the Syvash region, western part of the Black Sea region) and the Lower Dnipro wetlands. Therefore, it is a high abundance of steppe birds and the maximum number of rare steppe species which should be a specific ornithological indicator of the status of zonal landscapes in the dry steppe zone (especially within protected natural areas of Ukraine) rather than general avian species diversity including introduced, invasive species, synanthropes, etc.