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Which Forest Characteristics Shape Bird Abundance in Central European Forests? A Case Study Based on Common Breeding Bird Survey in Czechia
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Spatial co‐occurrence patterns are determined by environmental factors, such as food availability or habitat characteristics and by biotic associations. When resources are limited, competition which implies a dominant hierarchy can shape species assemblage. Here, we study space and time co‐occurrence of steppe passerines during the breeding season in a natural steppe habitat, its modulation by environmental filtering, potential biotic interactions and random processes. We applied the joint species distribution model of hierarchical modelling of species community (HMSC) to data on species presence–absence and environmental, temporal and spatial covariates acquired from seven plots in a natural steppe in central Spain during two consecutive years. Our results reveal the patterns of bird species co‐occurrence and suggest that this assemblage might be competitively structured. The assemblage appears to be configured around one dominant species, the Eurasian skylark, which establishes principally negative associations with many of the coexistent species. Our results contribute to the understanding of how competition and dominance processes, together with ecological constraints and other biotic associations, shape bird assemblages.
Aim
Despite the complexity of population dynamics, most studies concerning current changes in bird populations reduce the trajectory of population change to a linear trend. This may hide more complex patterns reflecting responses of bird populations to changing anthropogenic pressures. Here, we address this complexity by means of multivariate analysis and attribute different components of bird population dynamics to different potential drivers.
Location
Czech Republic.
Methods
We used data on population trajectories (1982–2019) of 111 common breeding bird species, decomposed them into independent components by means of the principal component analysis (PCA), and related these components to multiple potential drivers comprising climate, land use change and species' life histories.
Results
The first two ordination axes explained substantial proportion of variability of population dynamics (42.0 and 12.5% of variation in PC1 and PC2 respectively). The first axis captured linear population trend. Species with increasing populations were characterized mostly by long lifespan and warmer climatic niches. The effect of habitat was less pronounced but still significant, with negative trends being typical for farmland birds, while positive trends characterized birds of deciduous forests. The second axis captured the contrast between hump‐shaped and U‐shaped population trajectories and was even more strongly associated with species traits. Species migrating longer distances and species with narrower temperature niches revealed hump‐shaped population trends, so that their populations mostly increased before 2000 and then declined. These patterns are supported by the trends of total abundances of respective ecological groups.
Main Conclusion
Although habitat transformation apparently drives population trajectories in some species groups, climate change and associated species traits represent crucial drivers of complex population dynamics of central European birds. Decomposing population dynamics into separate components brings unique insights into non‐trivial patterns of population change and their drivers, and may potentially indicate changes in the regime of anthropogenic effects on biodiversity.
Species' geographical distributions and abundances are a central focus of current ecological research. Although multiple studies have been conducted on their elucidation, some important information is still missing. One of them is the knowledge of ecological traits of species responsible for the population density variations across geographical (i.e., total physical area) and ecological spaces (i.e., suitable habitat area). This is crucial for understanding how ecological specialization shapes the geographical distribution of species, and provides key knowledge about the sensitivity of species to current environmental challenges. Here, we precisely describe habitat availability for individual species using fine‐scale field data collected across the entire Czech Republic. In the next step, we used this information to test the relationships between bird traits and country‐scale estimates of population densities assessed in both geographical and ecological spaces. We did not find any effect of habitat specialization on avian density in geographical space. But when we recalculated densities for ecological space available, we found a positive correlation with habitat specialization. Specialists occur at higher densities in suitable habitats. Moreover, birds with arboreal and hole‐nesting strategies showed higher densities in both geographical and ecological spaces. However, we found no significant effects of morphological (body mass and structural body size) and reproductive (position along the slow–fast life‐history continuum) traits on avian densities in either geographical or ecological space. Our findings suggest that ecological space availability is a strong determinant of avian abundance and highlight the importance of precise knowledge of species‐specific habitat requirements. Revival of this classical but challenging ecological topic of habitat‐specific densities is needed for both proper understanding of pure ecological issues and practical steps in the conservation of nature. We test the relationships between traits of birds and country scale estimates of population densities assessed in both geographical and ecological space. We did not find any effect of the habitat specialization on avian densities in geographical space, but the effect turned positive once we recalculated the densities for ecological space available. Moreover, birds with arboreal and hole nesting strategies showed higher densities in both geographical and ecological space. However, we found no significant effects of the morphological and reproductive traits on avian densities.
Species abundances and distributions are changing in response to changing climate and other anthropogenic drivers but how this translates into how well species can match their optimal climate conditions as they change is not well understood. Using a continental-scale 30-year time series, we quantified temporal trends in climate matching of North American bird species and tested whether geographical variation in rates of climate and land use change and/or species traits could underlie variation in trends among species. Overall, we found that species abundances and distributions are becoming more decoupled from climate as it changes through time. Species differences in climate matching trends were related to their ecological traits, particularly habitat specialization, but not to average rates of climate and land use change within the species’ ranges. Climatic decoupling through time was particularly prominent for birds that were declining in abundance and occupancy, including threatened species. While we could not discern whether climate decoupling causes or is caused by the negative population trends, higher climatic decoupling in declining species could lead to a feedback as birds experience increasing exposure to suboptimal climatic conditions.
The book summarises recommendations on establishing, running, and improving national wild bird monitoring schemes. The methodology is described in detail and includes field methods, sampling design, data management and analysis, and communication; including case studies from various countries. The guide will be distributed among the Pan-European Common Bird Monitoring Scheme (PECBMS) network of cooperating individuals and organisations across Europe, as well as through the European Bird Census Council national delegates and BirdLife International partner organisations. We hope that the first edition will contribute to and help to improve the high scientific standard of bird monitoring in Europe.
Development of new bird monitoring schemes, as well as a need for improvements of existing schemes, brings an increasing need to use the highest level of scientifically sound methods for counting birds, analysing and presenting the data. Although general principles of bird monitoring are available in a form of textbooks and scientific papers, the information is scattered across many titles. Probably, more importantly, there is much good experience and practice across Europe, which can be shared and used for the development and improvement of monitoring schemes. Therefore, PECBMS, a common initiative of the European Bird Census Council and BirdLife International, decided to bring together and publish a Best Practice Guide summarizing the principles of good bird monitoring including case studies from European countries documenting details of various aspects of bird monitoring.
Count data can be analyzed using generalized linear mixed models when observations are correlated in ways that require random effects. However, count data are often zero-inflated, containing more zeros than would be expected from the typical error distributions. We present a new package, glmmTMB, and compare it to other R packages that fit zero-inflated mixed models. The glmmTMB package fits many types of GLMMs and extensions, including models with continuously distributed responses, but here we focus on count responses. glmmTMB is faster than glmmADMB, MCMCglmm, and brms, and more flexible than INLA and mgcv for zero-inflated modeling. One unique feature of glmmTMB (among packages that fit zero-inflated mixed models) is its ability to estimate the Conway-Maxwell-Poisson distribution parameterized by the mean. Overall, its most appealing features for new users may be the combination of speed, flexibility, and its interface's similarity to lme4.
Aim
Understanding the relative contribution of different species interactions in shaping community assembly has been a pivotal aim in community ecology. Biotic interactions are acknowledged to be important at local scales, although their signal is assumed to weaken over longer distances. We examine the relationship between positive, neutral and negative pairwise bird abundance distributions and the phylogenetic and functional distance between these pairs after first controlling for habitat associations.
Location
France and Finland.
Time period
1984 to 2011 (Finland), 2001 to 2012 (France).
Major Taxa studied
Birds.
Methods
We used results from French and Finnish land bird monitoring programmes, from which we created three independent datasets (French forests, French farmlands and Finnish forests). Separately for the three datasets, we fitted linear mixed‐effects models for pairwise abundance values across years per point count station to infer the association between all common species pairs, while controlling for geographical distribution and habitat associations, and saved pairwise regression coefficients for further analyses. We used a null model approach to infer whether the observed associations (effect sizes) differ from random. Finally, using quantile regression, we analysed the relationships between functional dissimilarity/phylogenetic distance and effect sizes.
Results
Our results show both negative and positive species interactions, although negative interactions were twice as common as positive interactions. Closely related species were more likely to show strong associations, both negative and positive, than more distant species across broad spatial scales. For functional dissimilarity, the results varied across datasets.
Main conclusions
Our results emphasize the potential of functional and phylogenetic proximity in generating both negative and positive species associations, which can produce pervasive patterns from local to geographical scales. Future assembly studies should refrain from strict dichotomies, such as compensatory dynamics versus environmental forcing, and instead consider the possibility of positive interactions.
Leaf litter invertebrates were sampled at eight sites, approximately 250 m apart in elevation, along an altitudinal transect extending from primary lowland rainforest to cloud forest in western Panama. The study focused on several diverse and numerically important litter invertebrate taxa (e.g., ants, spiders, and beetles) that were effectively sampled using a combination of litter sifting and test tube pitfall traps. The mean altitudinal range of species was around 500 m (standard deviation 370 m) and approximately 50% of the species characteristic of a given elevation dropped out after a 500 m change in elevation in either direction. There was no evidence for distinct altitudinal zonation in leaf litter assemblages. Both species richness and number of individuals of most taxa showed a pronounced decline in the vicinity of the upward transition to cloud forests. The data also suggest a broad mid-elevation peak in sample species richness for the litter invertebrate fauna. The implications of the results for biodiversity conservation are discussed.
The primary aim of this paper is to provide a pollen-based quantitative reconstruction of Holo-cene vegetation in order to update a perspective on natural vegetation in the Czech Republic and Slovakia. As a secondary aim we compare composition of this reconstructed Holocene vegetation with the composition of potential natural vegetation (PNV sensu Neuhäuslová et al. 1998) in the area studied. Based on 87 individual pollen sequences, we estimate the changes in Holocene vegetation that have occurred in nine circular regions, each 60km in radius. We obtained estimates of regional vegetation using the REVEALS model (Regional Estimates of VEgetation Abundance from Large Sites). This model considers pollen productivity, dispersal and taphonomic differences between taxa. The development of post-glacial vegetation can be divided into three general phases: Early, Middle and Late Holocene. Clustering of the interregional variability clearly separated lowlands from middle altitudes and mountains. The Early Holocene was dominated by semi-open pine forest in nearly all the regions studied. Mixed oak woodlands appeared in the Middle Holocene and only in the lowlands, while the rest of the area studied was dominated by spruce (> 32%) forest. The percentage of spruce remained high (> 19%) in fir-beech forests of the Late Holocene. The dominance and co-dominance of spruce at middle and high altitudes during the Middle and Late Holocene differs most from previous interpretations of pollen percentages. We attribute this to the climatic and edaphic conditions differing from those in other parts of central Europe at a similar altitude. Continuous presence of Poaceae (> 9%) and pioneer trees during the entire Holocene (Pinus > 6%) indicates an important role of factors sustaining their long-term abundance, be it herbivory, fire or other kinds of disturbance, natural and/or anthropogenic. The
The area of the Orlické hory Mts. has been characterised by decline and disturbances of Norway spruce (Picea abies/L./Karst.) stands since the 1980s. Currently, only three permanent research plots have been preserved from the original sixteen established plots in this region. In the present study, the health status, as indicated by defoliation, mortality, and stem radial growth, was studied in the peaty and climax spruce ecosystems in the upper elevations of the mountains from 1979 to 2014. This health status was correlated with ambient air pollution (SO2) as well as climate factors (temperature and precipitation). The health status of individual trees on the plots was determined by evaluation of the foliage status, and tree vitality was evaluated by measuring stem radial growth increment. Stress factor analysis showed that high air pollutant concentrations predisposed Norway spruce to stress from climatic events (drought, temperature changes), leading to forest decline. The most serious damage can be attributed to the combination of chemical and climatic stress. Stands with lowered vitality were attacked by secondary biotic pests (particularly bark beetle), resulting in rapid tree mortality. The damage process is marked not only by higher mortality, but also by chlorosis and necrosis of the needles. The stabilised trend in health status of the spruce stands was registered since approximately 1990s. In terms of climatic factors, the weather in June had the most visible influence on radial increment. Low temperatures and high precipitation were the limiting factors for radial growth in studied mountain area.
Increasing evidence indicates that species throughout the world are responding to climate change by shifting their geographic distributions. Although shifts can be directionally heterogeneous, they often follow warming temperatures polewards and upslope. Montane species are of particular concern in this regard, as they are expected to face reduced available area of occupancy and increased risk of extinction with upslope movements. However, this expectation hinges on the assumption that surface area decreases monotonically as species move up mountainsides. We analysed the elevational availability of surface area for a global data set containing 182 of the world' s mountain ranges. Sixty-eight per cent of these mountain ranges had topographies in which area did not decrease monotonically with elevation. Rather, mountain range topographies exhibited four distinct area-elevation patterns: decreasing (32% of ranges), increasing (6%), a mid-elevation peak in area (39%), and a mid-elevation trough in area (23%). These findings suggest that many species, particularly those of foothills and lower montane zones, may encounter increases in available area as a result of shifting upslope. A deeper understanding of underlying mountain topography can inform conservation priorities by revealing where shifting species stand to undergo area increases, decreases and bottlenecks as they respond to climate change.
Because of the slow accumulation and long residence time of carbon in biomass and soils, the present state and future dynamics of temperate forests are influenced by management that took place centuries to millennia ago. Humans have exploited the forests of Europe for fuel, construction materials and fodder for the entire Holocene. In recent centuries, economic and demographic trends led to increases in both forest area and management intensity across much of Europe. In order to quantify the effects of these changes in forests and to provide a baseline for studies on future land-cover–climate interactions and biogeochemical cycling, we created a temporally and spatially resolved reconstruction of European forest management from 1600 to 2010. For the period 1600–1828, we took a supply–demand approach, in which supply was estimated on the basis of historical annual wood increment and land cover reconstructions. We made demand estimates by multiplying population with consumption factors for construction materials, household fuelwood, industrial food processing and brewing, metallurgy, and salt production. For the period 1829–2010, we used a supply-driven backcasting method based on national and regional statistics of forest age structure from the second half of the 20th century. Our reconstruction reproduces the most important changes in forest management between 1600 and 2010: (1) an increase of 593 000 km2 in conifers at the expense of deciduous forest (decreasing by 538 000 km2); (2) a 612 000 km2 decrease in unmanaged forest; (3) a 152 000 km2 decrease in coppice management; (4) a 818 000 km2 increase in high-stand management; and (5) the rise and fall of litter raking, which at its peak in 1853 resulted in the removal of 50 Tg dry litter per year.
The common features of spectral reflectance from vegetation foliage upon leaf dehydration are decreasing water absorption troughs in the near-infrared (NIR) and short-wave-infrared (SWIR). We studied which leaf water index in the NIR and SWIR is most suitable for the assessment of leaf water content and the detection of leaf dehydration from the laboratory standpoint. We also examined the influence of the thickness of leaves upon leaf water indices. All leaf water content indices examined exhibited basic correlations with the relative water content (RWC) of leaves, while the R 1300/R 1450 leaf water index also demonstrated a high signal strength and low variability (R 2>0.94). All examined leaf reflectance ratios could also be correlated with leaf thickness. The thickness of leaves, however, was not independent of leaf RWC but appeared to decrease substantially as a result of leaf dehydration.
Forests in Flux
Forests worldwide are in a state of flux, with accelerating losses in some regions and gains in others. Hansen et al. (p. 850 ) examined global Landsat data at a 30-meter spatial resolution to characterize forest extent, loss, and gain from 2000 to 2012. Globally, 2.3 million square kilometers of forest were lost during the 12-year study period and 0.8 million square kilometers of new forest were gained. The tropics exhibited both the greatest losses and the greatest gains (through regrowth and plantation), with losses outstripping gains.
Biodiversity monitoring is important to identify conservation needs and test the efficacy of management actions. Variants of “abundance” (N) are among the most widely monitored quantities, e.g., (true) abundance, number of occupied sites (distribution, occupancy) or species richness.We propose a sampling-based view of monitoring that clearly acknowledges two sampling processes involved when monitoring N. First, measurements from the surveyed sample area are generalized to a larger area, hence the importance of a probability sample. Second, even within sampled areas only a sample of units (individuals, occupied sites, species) is counted owing to imperfect detectability p. If p < 1, counts are random variables and their expectation
E(n) is related to N via the relationship E(n) ÿ*p. Whenever p < 1, counts vary even under identical conditions and underestimate N, and patterns in counts confound patterns in N with those in p. In addition, part of the population N may be unavailable for detection, e.g., temporarily outside the sampled quadrat, underground or for another reason not exposed to sampling; hence a more general way of describing a count is E(n) ÿ*a*p, where a is availability probability and p detection, given availability. We give two examples of monitoring schemes that highlight the importance of explicitly accounting for availability and detectability. In the Swiss reptile Red List update, the widespread and abundant slow worm (Anguis fragilis) was recorded in only 22.1% of all sampled quadrats. Only an analysis that accounted for both availability and detectability gave realistic estimates of the species’ distribution. Among 128 bird species monitored in the Swiss breeding bird survey, de
tection in occupied 1 km quadrats averaged only 64% and varied tremendously by species (3–99 %); hence observed
distributions greatly underestimated range sizes and should not be compared among species.We believe that monitoring design and analyses should properly account for these two sampling processes to enable valid inferences about biodiversity. We argue
for a more rigorous approach to both monitoring design and analysis to obtain the best possible information about the state of nature. An explicit recognition of, and proper accounting for, the two sampling processes involved in most monitoring programs will go a long way towards this goal
This paper reports the long-term numerical trends of the thirty common forest bird species and explores changes in the community composition in the three main types of old-growth stands in the Białowieża National Park (E Poland, hereafter BNP) over 45 years (1975–2019). We present recent (2015–2019) data on abundance of birds for the seven study plots and pool them with the time series collected since 1975. The numbers of individual bird species strongly fluctuated, with most of the species showing alternating phases (the initial periods of population growth followed by the periods of population decline or stability). The numbers of 19 species increased; maximum growths by c. 3–5% per year included Columba palumbus, Dendrocopos major, Sylvia atricapilla and Regulus ignicapilla. Among a few declining species, Ficedula hypoleuca, Phylloscopus sibilatrix and F. parva experienced the strongest declines, respectively by 4.0%, 2.7% and 2.2% per year. Mostly the same species bred in the plots in the 1970s and in recent years, indicating a stable species pool. The total abundance peaked around 2005, declining thereafter in deciduous stands, but increasing further (along with the species richness) in the coniferous stands. The similarity index between the study plots
(beta-diversity) changed little over 45 years; ash-alder and lime-hornbeam stands remained most similar, while coniferous
forests stood more apart. The changes found in the old-growth stands of BNP (mostly coniferous fragments) could be partly explained by natural modification of the habitat structure and the processes acting in the large geographical scales, within or outside of the breeding grounds. The long-term studies such as the one in the BNP reported here, provide a basis for the rates of natural turnover in the bird communities in pristine habitats, directly unaffected by human impact.
Variation in bird community composition across habitats may be reflected by changes in species’ ecological characteristics. By their comparison between habitats, we can learn information about the factors underlying these changes. With this purpose, we used data from a nation-wide breeding bird monitoring scheme surveying birds in 15 habitat types sorted into four broad categories (forests, open, urban, and humid habitats) in a central European country, Czechia. We considered life-history strategy, migration distance, climatic niche position, European rarity, and diet niche as species’ ecological characteristics and compared their mean values across the habitat types. Although habitat type explained relatively low proportion of variability in these characteristics indicating that birds widely overlap in their habitat use, we observed significant differences in ecological characteristics between broad habitat categories, as well as between habitat types within a given category. For example, urban habitats hosted species with generally lower degree of insectivory than forest habitats. Within forests, coniferous stands hosted species with colder climatic niche than deciduous stands. The greatest differences were observed among humid habitat types: species recorded in water bodies were rarer in Europe and had slower life-history strategies than species recoded in running water. Within the open habitat category, mining areas were the most specific habitat with long-migrating and warm-dwelling species. The observed patterns can be driven by various factors including habitat-specific selection pressures, biogeographic constraints and human-induced habitat changes. On their basis, we discuss our findings.
Forest restoration is being scaled-up globally to deliver critical ecosystem services and biodiversity benefits, yet we lack rigorous comparison of co-benefit delivery across different restoration approaches. In a global synthesis, we use 25,950 matched data pairs from 264 studies in 53 countries to assess how delivery of climate, soil, water, and wood production services as well as biodiversity compares across a range of tree plantations and native forests. Carbon storage, water provisioning, and especially soil erosion control and biodiversity benefits are all delivered better by native forests, with compositionally simpler, younger plantations in drier regions performing particularly poorly. However, plantations exhibit an advantage in wood production. These results underscore important trade-offs among environmental and production goals that policymakers must navigate in meeting forest restoration commitments.
The variability in the amount and configuration of broad habitat types in the landscape, together with their structural complexity, influence observed biodiversity patterns. When considering structurally similar sites of the same habitat type, the variability in the abundance, species richness or diversity of organisms may be explained by the landscape context. To assess the numerical response of species to the landscape context, in terms of amount and configuration of forest environments, we investigated the bird assemblages of similarly structured forest habitats in an extensively managed forest region, encompassing different landscape contexts. We considered the numerical response of bird assemblages, in terms of abundance, species richness and diversity, and relative abundance of specific guilds, to the landscape context. We considered the forest cover at different spatial scales as a measure of habitat amount, while we quantified aspects of habitat configuration using various landscape metrics, and measured local forest structures. We found significant responses in multiple forest bird species to three important indices of forest structures: mean diameter of living trees, mean diameter of dead trees and volume of lying deadwood. Within similarly structured forest plots, bird assemblages showed responses linked with the landscape context, while plots with different habitat structure showed similar responses to the landscape context. In particular, there was a clear positive response of birds to the amount of broadleaf and mixed forest cover in the landscape. In addition, the distance between forest patches negatively affected species richness and diversity. Within landscapes, the increase of broadleaf in the existing forest area could boost abundance and diversity, decrease isolation levels for species dependent on broadleaves and enhance structural connectivity, generally favouring the majority of the species. Our findings suggest that the simple provision of habitat structures cannot represent a viable solution for biodiversity conservation and that the use of structural indicators of biodiversity like deadwood and age of canopy trees for assessing conservation value of forest needs to be integrated with landscape-scale indices. Our analysis clearly shows that the amount of habitat available in the surrounding landscape is linked with positive biodiversity responses. As human activities can alter both the provision of important habitat structures in stands across the landscape, as well as their overall landscape context, an integrated multi-scale biodiversity management is highly advisable.
Understanding the processes shaping the composition of assemblages in response to disturbance events is crucial for preventing ongoing biodiversity loss in forest ecosystems. However, studies of forest biodiversity responses to disturbance typically analyze immediate or short-term impacts only, while studies relating long-term disturbance history to biodiversity assemblage dynamics are rare. To address this important knowledge gap, we used a dendroecological approach to link natural disturbance history of 250 years (1750-2000) to structural habitat elements and, in turn, to breeding bird assemblages. We used data collected in 2017 and 2018 from 58 permanent study plots within 10 primary spruce forest stands distributed across the Western Carpathian Mountains of Europe. This dataset contained breeding bird counts and environmental variables describing forest density, tree diameter distribution, tree height, tree microhabitats, deadwood quantity and quality, and regeneration. Bird assemblages were significantly influenced by forest structure which was in turn shaped by disturbance dynamics (disturbance frequency, time since the last disturbance and its severity). Early successional species associated with more open habitats were positively influenced by disturbance-related structure (i.e. deadwood-related variables, canopy cover), while some species responded negatively. At the same time, overall abundance, species richness and Shannon diversity of the bird assemblage remained unchanged under variable disturbance histories. Our results support a view of primary spruce forests as a highly dynamic ecosystem, harbouring populations of bird species at all stages of succession despite significant structural changes and shifting patch mosaics over time due to natural disturbances.
Norway spruce (Picea abies) is one of the most important target trees in forestry. In Central Europe, it is grown primarily in forest plantations. However, the distribution area of this tree species is declining due to climate change and trends toward sustainable forest management. The question how artificial habitats such as plantations influence the native biota is still unclear. We aimed to investigate the influence of spruce plantations on bird communities at the country level. We focused on birds in relation to biotic, stand and land use characteristics. We studied bird communities (including woodpeckers) throughout the Czech Republic. All sites were situated in mature spruce forest plantations. Birds were sampled using the point count method, and nine environmental predictors were considered to potentially affect the bird community. Our results indicate that the representation of deciduous trees (within stands and in the surroundings) and longhorn beetles (as prey) have a predominant effect on the species richness of birds, including woodpeckers. The effects of longhorns and deciduous trees in the stand were positive, while deciduous forests in the surroundings had a negative effect. We also found several species associated with spruce, even in plantation forests. An important finding regarding the future management of spruce stands is that bird communities exhibited a strong relationship with spruce, even outside of its native range. Admixture with deciduous trees was favorable at the stand level, while at the landscape level, there is the need for adequate spruce-dominated forests, and deciduous forests may serve as obstacles. We argue that plantations cannot only be seen as tree farms or green deserts but also be used for biodiversity management. Nevertheless, it is important to leave deciduous trees within the stand until the end of the rotation period, as birds find food and nesting places in these trees.
The level of habitat specialization is informative in terms of animals’ population status and conservation concern. Therefore, identifying the areas where specialist species are aggregated and understanding the ecological constrains that might shape their distribution has become an important issue. In this sense, we tested whether specialist communities are more likely to succeed in milder and stable environments or in more extreme and less predictable environments. For that purpose, we used data from the EBCC atlas of European breeding birds and for each of 50 × 50 km grid cells calculated community specialization index (CSI). We expressed CSI in two ways: as a mean (CSIMEAN) and a standard deviation (CSISD) across species in a given cell. We used generalized least squares (GLS) models to relate these measures to geographic variables (latitude, longitude and altitude) and climatic variables (temperature and rainfall) across Europe controlling for possible confounding effects of habitat heterogeneity and human-induced land cover conversion. We identified two areas, Scandinavian Peninsula and the steppe regions north of Caucasus, where bird communities are highly specialised. GLS models showed that habitat specialization generally increased with altitude and this pattern was broadly shared by the CSIMEAN and CSISD. Concerning climatic variables, we found that specialist spatial distribution was significantly related to extreme temperatures and lower level of precipitation. Our results thus suggest that European specialist birds are found mostly in strongly seasonal, dry and cold environments. Thereby, preserving these sensible environments from further perturbations might be the key for the specialist conservation.
Large areas of montane forests are commercially harvested, while some other parts remain unmanaged. These conditions provide an opportunity to study the response of bird communities to forest management. Here we focused on the effects of tree species composition and tree age on bird species richness. We counted birds in two types of montane forest (beech and mixed) replicated in three age classes (managed 55-65 years, managed 85-95 years, unmanaged over 200 years) in the Vtačnik Mountains, Slovakia. Number of bird species at individual study sites (local richness) was predicted solely by the tree age and not by the forest type. Specifically, the number of species was highest in the oldest stands, while the stands of 55-65 and 85-95 years did not differ from each other. By contrast, forest type seems important for total bird species richness (number of species recorded in all study sites of a given type) with more species recorded in mixed forests than in beech forests. The local richness seems thus limited by the amount resources available at a given site, which is highest in the oldest stands irrespective to forest type, probably due to largest amount of food, dead wood or tree cavities, being particularly suitable for habitat specialists. However, larger species pool in mixed forest, enriched by birds adapted to coniferous trees, increases the total number of species observed in this type. We thus recommend to shift the harvest to the highest possible age and to include some other tree species into parts of beech monocultures.
Ecological specialization provides information about adaptations of species to their environment. However, identification of traits representing the relevant dimensions of ecological space remains challenging. Here we endeavoured to explain how complex habitat specializations relate to various ecological traits of European birds. We employed phylogenetic generalized least squares and information theoretic approach statistically controlling for differences in geographic range size among species. Habitat specialists had narrower diet niche, wider climatic niche, higher wing length / tail length ratio and migrated on smaller distances than habitat generalists. Our results support an expected positive link between habitat and diet niche breadth estimates, however a negative relationship between habitat and climate niche breadths is surprising. It implies that habitat specialists occur mostly in spatially restricted environments with high climatic variability such as mountain areas. This, however, complicates our understanding of predicted impacts of climatic changes on avian geographical distributions. Our results further corroborate that habitat specialization reflects occupation of morphological space, when specialists depend more on manoeuvrability of the flight and are thus more closely associated to open habitats than habitat generalists. Finally, our results indicate that long distance movements might hamper narrow habitat preferences. In conclusion, we have shown that species’ distributions across habitats are informative about their positions along other axes of ecological space and can explain states of particular functional traits, however, our results also reveal that the links between different niche estimates cannot be always straightforwardly predicted.This article is protected by copyright. All rights reserved.
The bird-habitat relationships proposed by Hamel (1992) represent the most comprehensive description of habitat suitability for all birds that breed and/or winter in forests of the southern United States. These relationships were developed from compilations of published census and natural history data, field experience, and expert opinion. As such, these relationships can be considered untested models of bird-habitat associations. We tested the ability of these models to predict the distribution of 25 common breeding birds among the forest habitat types of the Southern Blue Ridge physiographic province. We used point-count survey data from national forests in Virginia, Tennessee, and Georgia to test the models. Thirteen of 25 models (52%) performed well (i.e., positive association between ranks from model predictions and ranks from the observed data) on the Tennessee data, while only 33% and 23% of the models performed well on the Georgia and Virginia data, respectively. Models for some species with distributions restricted to mid-aged to mature deciduous habitats (e.g., black-and-white warbler [Mniotilta varia] and black-throated blue warbler [Dendroica caerulescens]) and/or restricted to high elevations (e.g., veery [Catharus fuscescens]) performed well across study sites. However, models for other mature deciduous forest species did not perform as well because these species (e.g., ovenbird [Seiurus aurocapillus], scarlet tanager [Piranga olivacea], and wood thrush [Hylocichla mustelina]) tended to occur more frequently than predicted in early age classes or mixed forest types. For these species, we suggest that early-aged deciduous habitat types be considered marginal habitat (rather than unused, as defined in Hamel's publication) for these relatively widespread forest birds in the Southern Blue Ridge region. Models for habitat generalists (e.g., Carolina chickadee [Poecile carolinensis], Carolina wren [Thryothorus ludovicianus], and red-eyed vireo [Vireo olivaceus]) did not perform well. We suggest that Hamel's models be used cautiously for most birds in mature forest habitats. Further tests of these models are needed to clarify the discrepancies between the predicted and observed patterns of habitat use we observed.
Bird populations were sampled between May 30 and July 20, 1972, on twenty-four 0.08-ha plots on Walker Branch Watershed, a primarily deciduous forest located in Anderson County, Tennessee. Univariate analysis of variance was used to test for differences in abundance categories of each bird species with respect to 28 habitat variables. Differences in habitat preferences within major bird families (Picidae, Parulidae, Paridae, and Thraupidae) were apparent from this analysis. Discriminant function analysis was therefore used to order the variables according to their strength in separating abundance categories for 13 of the more abundant bird species. This analysis indicated that some bird species were distributed according to specific habitat variables. For example, Downy Woodpecker abundance was highly correlated with the number of saplings on a plot. Distributions of other species (e.g., the Scarlet Tanager) were not strongly related to any single variable but were related weakly to a large number of variables. The results form a basis for predicting avifaunal composition changes resulting from alteration of habitat structure.
Managing for forest wildlife requires attention not only to quantity but quality of forests within the landscape. We examined the extent to which local structural attributes and landscape context of forest stands explained variation in density and reproductive success of mature forest birds across 12 sites in southeast Ohio, USA, 2004-2006. Results suggest that several structural characteristics influenced bird— habitat relationships in our study. Densities of 3 songbird species (i.e., ovenbird [Seiurus aurocapilla], cerulean warbler [Setophaga cerulea], and scarlet tanager [Piranga olivacea]) were positively related to canopy openness, which is usually a function of canopy gaps. Habitat attributes described by ground litter, understory density, and canopy height were positively associated with densities of ground (i.e., worm-eating warbler [Helmitheros vermivorum]), or shrub nesting species (i.e., Kentucky and hooded warblers [Geothlypis formosa and Setophaga citrina], respectively). Furthermore, the number of small trees likely drove the positive relationship between density of wood thrush (Hylocichla mustelina), a subcanopy nester. After accounting for temporal variability in daily nest survival rates, the odds of nest survival for all species increased 10.5% for every 1% increase in canopy openness and decreased 1.4% for each 5% increase in understory vegetation density. Habitat—nest survival relationships were not apparent at the level of the individual species. Our results suggest that structural attributes produced by increasing habitat heterogeneity may be necessary for conservation of forest bird communities.
Mixed montane forests cover large tracts of the low mountain ranges that dominate Central Europe and also contain much of the area that is important to forest related nature conservation. However, beyond general patterns little is known about ecologically effective driving factors in this habitat. This results in a lack of precise values that can be used to formulate guidelines for nature conservation oriented management strategies. To improve this situation, we used birds as indicators for forest habitat qualities.
Differences in vascular plant species richness; along the altitudinal gradient in the Aurland area of western Norway have been investigated. Based on field surveys, as complete lists as possible of all vascular plants have been compiled for each 100 m altitudinal band, from sea level to the highest mountain (1764 m). For each of the 18 altitudinal bands, climatic data have been estimated. A total of 444 vascular plant species were recorded. Highest species richness (263 species) occurred in the 600–700 in band, whereas the uppermost band had only 10 species. There are minor differences in species number between the altitudinal bands < 1000 m. Partial least squares regression shows that species richness for the overall altitudinal gradient is well predicted by mean July and January temperatures and mean annual precipitation. Species turnover is highest in the 100–200 m. 600–700 m. and 1400–1500 m altitudinal bands. In terms of the gradient in summer temperature, the study supports the generally assumed linear relationship between July temperature and the number of vascular plant species between 700 and 1500 m corresponding with a mean July temperature range of 7–11°C. The study shows a decrease of ca 30 vascular plant species with a 1°C decrease in mean July temperature, and that the “climatic vascular plant limit” is here estimated to occur at a mean July temperature of 2.4°C. Above 1500 and below 700 m. species number is lower than expected based on summer iemperature conditions alone. The 700–800 m band represents the highest floristic difference compared to the other bands. Ordination and classification analyses of the floristic compositional data of all the bands highlight the 600–800 and 1500–1600 m altitudinal bands as the major biotic boundaries along the gradient. No major discontinuity in species richness, composition, or turnover was consistently found, however, at the 1100–1200 m band representing the forest-limit ecotone in Aurland.
Species richness is the most widely used measure for the diversity of a biological community. Unfortunately, the number of species counted is usually a biased measure, as not all species present may be detected. Use of species counts as a proxy for true species richness requires the assumption of constant (over space and time) species detectability. This index assumption is hardly ever tested and, if violated, comparisons over time, space or other dimensions, for example different habitats, will be distorted. In monitoring programmes one therefore needs to know the proportion of species present that are detected and how this proportion is affected by external factors.
We used capture–recapture techniques to calibrate the Swiss breeding bird survey, where species richness is recorded annually in c. 270 1‐km ² quadrats during two to three visits and interest is focused on annual trends and regional comparisons. Hitherto, analysis has been restricted to species counts, while species detectability and its determinants are not known. We used the interpolated jackknife estimator to compute mean species detectability for 268 quadrats in 2001–03 and tested determinants of detectability related to space, time, observer, survey effort and biology.
Mean species detectability averaged 0·89 (SD 0·06, range 0·72–1·00), with no significant difference among years and significant, but small, regional differences. Observers differed, but surprisingly not in relation to their experience in a quadrat. Detectability was positively related to mean visit duration. Larger communities had a lower mean species detectability. A slight violation of population closure because of staggered arrival of migrants did not introduce any measurable bias into our results.
Synthesis and applications. Species detectability in the Swiss programme was high and varied little in relation to recognized sources of heterogeneity. Nevertheless, increased standardization should be considered for mean visit duration. While these results are pleasing for the Swiss programme and show that using counts as indices of species diversity need not always induce serious bias, conditions in other programmes, and in the future in the Swiss programme, may be quite different. Both in monitoring programmes and in ecological studies, as a way of risk minimization, species richness ought to be rigorously estimated whenever possible to avoid detection of spurious effects because of changes in species detectability.
This example is provided so that non-theorists may see actual applications of the theory previously described. The Dickcissel sex ratio is employed as an indirect index of suitability. A sex ratio index was found to be correlated positively with density. This is consistent with the hypothesis that territorial behavior in the males of this species limits their density. This study provides a valid example of how the problem can be approached and offers a first step in the eventual identification of the role of territorial behavior in the habitat distribution of a common species.
In recent decades, European protected forest areas primarily dedicated to biodiversity conservation have been increasingly selected using standard criteria that refer to three guiding principles in conservation planning: sufficient representativeness, adequate spatial design and adequate site suitability. The way these criteria are currently used by land planners was assessed through a standardised questionnaire sent to representatives from 21 European countries involved in the COST E27 action, and compared to prescriptions from the scientific literature. Results show that only 26% of the 101 types of protected forest areas, distributed in nine different countries, have been selected on the basis of all three guiding principles. For many protected area networks, insufficient importance is given to spatial design and site conditions, with the result that long-term persistence of biodiversity is far from guaranteed. The use of quantitative objectives, operational targets and optimisation approaches is also infrequent, in spite of repeated commitments of European forest ministers (MCPFE) to establish coherent, comprehensive and representative forest conservation networks. Overall, the adoption of a more systematic approach in forest conservation planning seems to be hindered by a dearth of operational guidelines to assess spatial design and site suitability, by insufficient collaboration between biologists and land planners, and by a shortage of funding to establish conservation networks.
The study deals with the challenge of adjusting inconsistencies in the historical data series over time for the main forest resources parameters (forest area, growing stock and increment) based on the UNECE/FAO Forest Resources Assessments (FRA) source data. It describes the methods used to improve the quality of long-term series based on national inventory data and assesses trends for a number of European countries. It attempts to identify driving forces behind major long-term changes in key forest resources parameters.
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