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Long-Term Changes in Breeding Bird Community of a Primeval Temperate Forest: 45 years of Censuses in the Białowieża National Park (Poland)
Abstract
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.
... One of such valuable fragment, being remnants of lowland European deciduous forests, is an iconic Białowieża Forest. It plays the role of a kind of natural laboratory where is possible to study natural processes that occur without significant human influence (Blondel 2022; Wesołowski et al. 2022). Breeding bird communities have been studied in this forest since 1975 (Tomiałojć et al. 1984;Wesołowski et al. 2022), but these studies are mainly based on the structure and dynamics of breeding communities. ...
... It plays the role of a kind of natural laboratory where is possible to study natural processes that occur without significant human influence (Blondel 2022; Wesołowski et al. 2022). Breeding bird communities have been studied in this forest since 1975 (Tomiałojć et al. 1984;Wesołowski et al. 2022), but these studies are mainly based on the structure and dynamics of breeding communities. Our study is the first one considering the functional diversity of bird assemblages in primeval, temperate forests. ...
... We also aimed to identify mechanisms that may shape the functional diversity of bird composition in temperate primeval forests. We hypothesize that functional diversity should be higher in ash-alder forests, due to the fact that these habitats have been recognized as the richest in bird species since the initial ornithological research conducted in the 1970s (Tomiałojć et al. 1984;Wesołowski et al. 2022). Among tree layers, we consider the highest FD among a tree crown, as canopy volume has been regarded as one of the main drivers of bird species diversity in temperate forests (Bae et al. 2018). ...
Functional diversity of bird assemblages has been disproportionally less recognized than taxonomic diversity. Especially, it has been less assessed in temperate primeval forests, serving as a reference point to the vast majority of forests more or less transformed by human activity. Therefore we aimed to determine the functional diversity of bird assemblages at the three levels of forest ecosystem organization: forest types, forest layers, and forest structures, and to determine mechanisms shaping the functional diversity of bird composition under primeval conditions of the Białowieża National Park (NE Poland). We used observations from a regular network of 96 points within six permanent plots in ash-alder and oak-lime-hornbeam forests, and we calculated functional diversity components and community-weighted mean values of birds’ functional traits. Despite higher taxonomic diversity and functional richness in the ash-alder forest, we found higher values of other functional diversity indices the in oak-lime-hornbeam forest. We also found differences in taxonomic and functional diversity among forest layers. We attributed mechanisms shaping the bird assemblages in ash-alder forests with habitat filtering, while niche partitioning or limiting similarity in oak-lime-hornbeam habitat. Bird assemblages on the crown and emergent layers seem to be shaped by niche partitioning mechanisms, whereas bird composition at shrub and understory levels seems to be shaped by habitat filters. Our study revealed that structural diversity at all three levels is crucial for maintaining the functional diversity of bird assemblages in the primeval forest.
... On the remaining four plots (L-riverine, 25 ha, M-lime-hornbeam, 30 ha, NE and NW-coniferous forests, both 25 ha) we also performed point counts. For the most recent description of the forest habitats on the plots, see Wesołowski et al. (2022). ...
... During the surveys, observers moved slowly across the plots and recorded all seen or heard singing birds on the maps (1:1000 scale), Point counts were performed on all seven plots, while territory mapping on areas enveloped with red lines (entire plots or parts of the plots). The results from C, K and W plots, where territory mapping in two approaches was done were used in this study, while standard territory mapping only was performed on the NW plot Wesołowski et al. 2022) and given the results reported in the current paper, these absolute numbers can be underestimated, but should show trends properly with additional details (i.e. pair seen, birds with nest material, alarm calls or feeding young) noted when available. ...
The effectiveness of surveys of breeding birds varies due to multiple factors, with the primary being imperfect detection, which is particularly severe for elusive species. For example, the territory mapping method requires surveying an area multiple times a season to compensate for missing individuals during single surveys. Novel methods require much less effort in the field and include estimation of both detection probability and abundance corrected for individuals that went undetected. The aim of this study was to check if point counts and model-based results provide estimates similar to the ones from the territory mapping method. We studied the abundance of two forest birds—Goldcrest Regulus regulus and Firecrest R. ignicapilla—on three permanent census plots in the Białowieża Forest (E Poland). We compared abundance estimates resulting from the territory mapping method in its ‘standard’ (~ 10 visits) and intensive (~ 20 visits) approaches. We also performed point counts at the same plots using distance sampling methodology and hierarchical models in an attempt to get unbiased estimates by correcting for imperfect detection. We found that the standard territory mapping method produces much lower abundances than model-based estimates, which was particularly evident for the more numerous Firecrest. At the same time, results from point counts were more consistent with numbers from the intensive territory mapping. Our findings suggest that applying point counts and distance sampling models meet modern standards by considering various effects in abundance, availability and detection processes along with providing uncertainty of their estimates. We assume that our results might be applicable to other elusive species.
... To inform recommendations on the minimum distances between automatic recording devices, we compared the detection distances of individual species with the average sizes of their territories. As reference values for the latter, we adopted the sizes of the territories found in a natural lowland forest, the Bialowieza Forest 18 . The values were converted from average densities. ...
... For species with lower detectability, the highest probability value goes to zero (*). Territory radii are based on density measures from Bialowieza primaeval forest and represent the minimum and maximum range obtained over several years of study 18 . Maximum ranges for small specialised species are inflated due to the probable heterogeneity of the habitat ( † ). ...
Passive acoustic monitoring has proven to have many advantages for monitoring efforts and research activities. However, there are considerations to be taken into account regarding the placement of autonomous sound recorders. Detection ranges differ among species and in response to variable conditions such as weather or the location of vocalising animals. It is thus important to the success of a research project to understand, with a certain degree of confidence, the distances at which birds might be detected. In two types of forests in Poland, we played back the vocalisations of 31 species of European forest birds exemplifying different singing characteristics. Based on recordings obtained along a 500-m transect, we estimated the probability of detection and maximum detection distance of each vocalisation. We broadcasted the recording at three heights of singing and repeated playbacks three times during the breeding season to evaluate the effect of vegetation growth. Our results revealed that environmental and meteorological factors had a significant influence on both detection probability and maximum detection distances. This work provides comprehensive measurements of detection distance for 31 bird species and can be used to plan passive acoustic monitoring research in Europe, taking into account species traits and individual characteristics of the study area.
... The Jura and Hessen study areas consisted of medium to large forest areas (~10-700 km 2 ) of mostly common beech (Fagus sylvatica) (Maag et al., 2022); WNP of one relatively large forest area (~46 km 2 ) of mostly pedunculate oak (Quercus robur), sessile oak (Q. petraea), and Scots pine (Pinus sylvestris) (Szymkowiak & Thomson, 2019); and BNP of a large, protected forest area (~105 km 2 , Polish part of BNP) of mostly hornbeam (Carpinus betulus), lime (Tilia cordata), and pedunculate oak (Wesołowski et al., 2022). ...
... In all study areas, abundance was measured by territory mapping. In Jura, observed abundances were provided by the national monitoring scheme of the Swiss Ornithological Institute (Knaus et al., 2021); in Hessen, by the national monitoring scheme of the Dachverband Deutscher Avifaunisten DDA (Wahl et al., 2020); and in WNP and BNP, respectively, by established monitoring in the study areas (Szymkowiak & Thomson, 2019;Wesołowski et al., 2022). In Jura and Hessen, the relative abundance per year was calculated in percentage of the mean yearly abundance (=100%) from 1990 to 2021 and in percentage of the abundance in the reference year of 2006, respectively; in WNP and BNP, abundances are territories per 1 km 2 . ...
Mast seeding is the episodic, massive production of plant seeds synchronized over large areas. The resulting superabundance of seeds represents a resource pulse that can profoundly affect animal populations across trophic levels. Following years of high seed production, the abundance of both seed consumers and their predators increase. Higher predator abundance leads to increased predation pressure across the trophic web, impacting nonseed consumers such as the wood warbler Phylloscopus sibilatrix through increased nest predation after tree mast years. Over the past 30 years, the frequency of tree seed masts has increased, while wood warbler populations have declined in several regions of Europe. We hypothesized that increasing mast frequencies may have contributed to the observed population declines by creating suboptimal breeding conditions in years after masting. We measured reproductive output in four study areas in central Europe, which was between 0.61 and 1.24 fledglings lower in the years following masting than nonmasting. For each study area, we used matrix population models to predict population trends based on the estimated reproductive output and the local mast frequencies. We then compared the predicted with the observed population trends to assess if the frequency of mast years had contributed to the population dynamics. In Wielkopolska National Park (PL) and Hessen (DE), masting occurred on average only every 4 years and populations were stable or nearly so, whereas in Jura (CH) and Białowieża National Park (PL), masting occurred every 2 and 2.5 years, respectively, and populations were declining. The simple matrix population models predicted the relative difference among local population trends over the past 10–20 years well, suggesting that the masting frequency may partly explain regional variation in population trends. Simulations suggest that further increases in mast frequency will lead to further declines in wood warbler populations. We show that changes in a natural process, such as mast seeding, may contribute to the decline in animal populations through cascading effects.
... t. tridactylus) in Poland, but even here it is significantly more common in protected areas compared to managed stands (Walankiewicz et al. 2002(Walankiewicz et al. , 2011Wesołowski et al. 2005;Piotrowska and Wesołowski 2007;Czeszczewik et al. 2013). In the Białowieża Forest, the species inhabits both spruce and spruce-pine forests and deciduous forests, mainly ash-alder stands, reaching breeding density of up to 0.3 pairs/10 ha in the Białowieża National Park (hereinafter BNP) (Wesołowski et al. , 2022. ...
Despite a clear preference of the Eurasian Three-toed Woodpecker Picoides tridactylus for spruce trees as foraging sites by both males and females, some studies showed intersexual resource partitioning that allows competition for food to be minimized. The objective of the study was to characterize foraging sites of the Three-toed Woodpecker in the primeval stands of the Białowieża National Park (BNP, Poland) in relation to sex. Although the woodpeckers foraged on seven tree species, both males and females foraged predominantly on spruce (83% and 90% of the observations, respectively). Selection indices showed a significant preference for dead spruce trees for both sexes and additionally for live spruce trees in the case of females. Spruce trees where woodpeckers foraged were twice as thick as those available, regardless of whether they were dead or alive. The only feature differentiating the feeding sites of males and females was the diameter of the part of the tree at foraging locations. This suggests that there is some niche partitioning between the sexes of the Three-toed Woodpecker in primeval stands of the BNP. Our research clearly showed that even in the very rich environment of the BNP, abounding in various forms of dead wood, large dead spruce trees are crucial for the Eurasian Three-toed Woodpecker.
... The undergrowth layer also featured a rich mix of shrubs, including black elderberry Sambucus nigra, hazelnut Corylus avellana, and Ribes sp. (Wesołowski et al. 2022). The second and third sample plots were located in a lime-hornbeam forest (30 ha each), characterized by a dense canopy and poorly developed undergrowth (Tomiałojć et al. 1984). ...
Although the robin is a quite common Eurasian bird, little is known about the phenomenon of extra-pair paternity (EPP) within this species, mainly due to its extremely secretive behavior during the breeding season. This study for the first time reveals the level of EPP of the continental subspecies under the primeval forest condition. To analyze the EPP frequency, genetic methods were used (microsatellite genotyping). Three research plots (~30 ha each) were established in a lime-hornbeam and riverine forest, in Białowieża National Park (north-eastern Poland) - the most primeval, lowland forest in the entire temperate zone. The study was conducted in 2018-2019 during the robin’s breeding season (late March - late June) using a combined mapping technique. Upon locating the nests, tail feathers, which were used as a source of DNA, were collected from entire robin families, including adults captured via mist nets. In total genetic material was obtained from a total of 70 robin families. Genotypes of social parents were compared with genotypes of nestlings to assess the occurrence of EPP and identify extra-pair males. We found evidence of EPP in 5.7 % of nests. Accordingly, 5.1 % of nestlings were the offspring of extra-pair males. We accept the assumed hypothesis of the low frequency of extra-pair paternity in the European robin population under the primeval forest condition. The explanations for the low level of EPP can be found in the robins begging behaviour in the pre-breeding period and the female constraint theory.
... It was described that tropical bird communities, far from being stable, are highly dynamic with a complex mix of stable and variable behaviour that generate changes in richness and density at spatial and temporal scales (Renner & Bates, 2020). In temperate forests (Poland), Wesołowski et al. (2022) found that the abundance of bird species strongly fluctuated, with most of the species showing alternating phases (growth followed by periods of decline or stability) in old-growth forests over 45 years . However, the structure of the bird community remained similar. ...
Long‐term studies have proven to be important to characterize animal communities and analyse the ecological responses to climate and environmental changes. These studies are necessary to determine the natural community variability (e.g., richness and density) to develop better conservation strategies to face climate changes. Here, we analysed the natural changes in the structure and functional traits of bird communities over 13 consecutive years (2010–2022) and determined the number of years of sampling needed to obtain a good estimation of the community structure variables in deciduous high latitude Nothofagus forests. Using point counts, we studied closed (80% of canopy cover) and open (40% of canopy cover) forests inside the Tierra del Fuego National Park. Species richness, density, biomass, and functional traits (migratory status, trophic groups, nest type, and feeding strata) were analysed using generalized linear models with forest type (closed and open) and year (2010–2022) as the main factors, while the standard error (SE) of sampling obtained from one to 12 sampling years was compared. Richness was significantly higher in open forests ( p < 0.01), while density and biomass were higher in closed forests. Additionally, density and biomass significantly varied among years in both forest types (e.g., lower density in 2013, 2014 and 2015, and higher in 2019). The density of birds for some functional traits also varied among years and forest types (e.g., higher values of cavity nesters in closed forests during 2019). Five to six years of sampling were needed to have an acceptable estimation of richness (20% SE), between 10 and 12 years for density, and >12 years for biomass. This study highlights the importance of long‐term studies to visualize natural variations in undisturbed habitats along time.
... Songbird population changes show much variation within their distribution area, but main trends based on long-term studies can be determined (Reif 2013, Hanzelka et al. 2015, Buchanan et al. 2016, Brlík et al. 2021, Reif et al. 2022, Wesołowski et al. 2022, Virkkala et al. 2023. Based on our current results, the annual number of adult Garden Warblers and Barred Warblers showed a decreasing trend during the study period. ...
This study aimed to monitor the demographic changes of some closely related species based on bird ringing data from the CES (Constant Effort Sites) program in Hungary between 2007 and 2018, and to explore the reasons for these demographic changes. The CES program tracks breeding bird populations with standard methods. The studied species breeding in Hungary were from genera Sylvia , Curruca, and Phylloscopus . Among these species, the trends of some forest birds, like Eurasian Blackcap (Sylvia atricapilla) , Lesser Whitethroat (Curruca curruca) , Common Chiffchaff (Phylloscopus collybita) and Willow Warbler ( Ph. trochilus) showed no substantial changes, and one of the open-habitat species, the Barred Warbler (Curruca nisoria) – a long distant migrant – showed decreasing trends. The Garden Warbler (Sylvia borin) – a trans-Saharan migrant but forest dweller – also experienced population declines. Short-distance migrants maintained stable populations. Common Whitethroat productivity displayed an increasing trend to compensate for population decline. Upon examining the Eurasian Blackcap, this study detected a strong relationship between the number of adult birds, productivity, and the number of adults captured the following year.
... For species with lower detectability, the highest probability value goes to zero (*). Territory radii are based on density measures from Bialowieza primaeval forest and represent the minimum and maximum range obtained over several years of study 12 The effects of SPL and peak frequency were consistent across species. For some smaller species, the detection probability dropped rapidly at a certain distance (Fig. 4). ...
Passive acoustic monitoring has proven to have many advantages for monitoring efforts and research activities. However, there are considerations to be taken into account regarding the placement of autonomous sound recorders. Detection ranges differ among species and in response to variable conditions such as weather or the location of vocalising animals. It is thus important to the success of a research project to understand, with a certain degree of confidence, the distances at which birds might be detected. In two types of forests in Poland, we played back the vocalisations of 31 species of European forest birds exemplifying different singing characteristics. Based on recordings obtained along a 500-m transect, we estimated the probability of detection and maximum detection distance of each vocalisation. We simulated three heights of singing and repeated playbacks three times during the breeding season to evaluate the effect of vegetation growth. Our results revealed that environmental and meteorological factors had a significant influence on both detection probability and maximum detection distances. This work provides comprehensive measurements of detection distance for 31 bird species and can be used to plan passive acoustic monitoring research in Europe, taking into account species traits and individual characteristics of the study area.
Species distribution and resource utilization are a fundamental aspect of ecology. By analyzing the tree space usage by birds and determining the species composition of birds across different parts of trees, our study could shed light on the mechanisms shaping co-occurrence patterns in bird communities. Therefore, our study aimed to determine the species composition of birds across different parts of trees. We investigated whether species richness differs between positions on a tree and how these positions influence the probability of occurrence of the 10 most frequently observed bird species. To achieve this, we observed birds within permanent plots in Białowieża National Park (BNP) and analyzed the distribution patterns of birds within six vertical and three horizontal sectors of trees. The compositional dissimilarity between tree sectors was assessed using detrended correspondence analysis. We employed generalized linear mixed-effects models to examine differences in species richness. The majority of the BNP bird community was associated with the branches, while other birds occupied the tree crown trunks and the understory trunks. Species richness was the highest on branches in the crown part of trees, followed by lower species richness on trunks associated with crowns, and the lowest richness was observed on branches and trunks in the understory. These results indicate that branches in the middle and lower parts of the crown serve as avian diversity hotspots on trees, likely due to the abundance of various food sources. The differing patterns of tree usage by specific bird species may suggest the avoidance of interspecific competition for resources. The study results of tree usage by bird species obtained in the primeval forest provides a reference point for studies conducted in human-altered woods. K E Y W O R D S niche partitioning, spatial ecology, species co-occurrence, tree usage, vertical stratification
Most populations of the european pied flycatcher Ficedula hypoleuca are decreasing. Different reasons for the decline are discussed, including biotic interactions and climate change. It is evident that many studies have been conducted in populations depending completely on nest boxes, but the influence of this artificial support on population dynamics is not well understood. we investigated the population dynamics of the pied flycatcher in the Kottenforst, an old-growth forest in western Germany, using recent data as well as historical records. we also determined the proportion of pairs breeding in nest boxes vs. natural nesting places. Specifically, we quantitatively analysed forest structure around tree holes occupied by the pied flycatcher. we found a continuous increase in population size since its establishment in the 1960s, which contrasts with overall long-term population trends in europe as well as the regional trend. whereas importance of nest boxes decreased over recent years, the majority of pairs are occupying tree holes for breeding, which are abundant in the richly structured,
open old-growth forest. This forest structure seems to be optimal for the pied flycatcher since it allows flying insects to be hunted close to the nest. finally, we discuss how forest structure and age as well as tree hole and insect availability may determine population trends of the pied flycatcher and highlight the importance of long-term studies.
Despite its broad range and high abundance, nest sites of the European robin Erithacus rubecula, a small forest passerine, are rarely characterised, and most studies refer to human-transformed habitats. In this paper, we describe the species’ nest sites in the natural conditions of a primeval forest. We also investigate robin preferences to address nest site selection which can only be assessed if the availability of potential nest sites is known. We studied robins’ nest sites in Białowieża National Park, eastern Poland, on three study plots (~30 ha each) in 2016–2019. Among all nests found (n = 165), the majority (118, ~72%) were found in tree holes, followed by ground nests (25, ~15%) and root-soil plates (22, ~13%). When the availability of cavities and root-soil plates is accounted for, it appears that robins preferred tree holes over plates. Robins appeared to be weakly selective in respect to tree species, preferring hornbeam Carpinus betulus, small-leaved lime Tilia cordata and Norway spruce Picea abies over other trees. Since both cavities and root-soil plates are superabundant in the Białowieża Forest, but scarce or absent in the heavily transformed robin breeding habitats of Western Europe (parks, orchards, hedgerows or managed forests), ground-nesting may predominate there simply due to these choice limits. In summary, our results provide a basis for understanding how original nest-site choices that evolved in natural, unmodified habitats can change when a species adapts to human-transformed habitats.
Climate warming could lead to ‘mis-matching’ of birds’ breeding times with availability of their invertebrate food resources. Fluctuating spring temperatures could influence variation in the commencement of egg-laying, as well as, in phenology of their resources (e.g., tree bud burst, appearance of folivorous caterpillars). We studied timing of Dendrocopos leucotos, Dendrocoptes medius, Dendrocopos major, Dryobates minor, and Picoides tridactylus breeding in, free of direct human intervention, strictly protected fragments of Białowieża Forest (Poland) in 1975–2019. We related their onset of breeding to inter-year variation in spring weather, trees’ bud burst and timing of folivorous caterpillars’ availability. Individual species initiated breeding at dates differing by a month. In spite of intraseasonal differences in the absolute laying dates, sometimes exceeding three weeks, the sequence of laying by different species within a season was highly repeatable; D. leucotos commenced the first and P. tridactylus the last. Within a species and season, the females commenced laying synchronously; usually 50% of them begun laying ≤ 8 days of each other. All species bred earlier when spring temperatures got higher. Nestling time of D. medius and D. major broadly coincided with ‘caterpillar peaks’, while D. minor young appeared too late. All woodpeckers advanced egg-laying in Białowieża National Park over 45 years but the inter-specific sequence of laying has been retained. These could be responses to strong advance of snow disappearance and to warming of the second half of April. The early recent laying dates remained within the range of earlier recorded ones, the early springs just became more frequent. Thus, the phenological acclimatization could be achieved by plastic behavioural and physiological adjustments. Lack of data on types of food actually used and their seasonal variation hinders mechanistic understanding of how warming would affect the future food supply and breeding performance of birds.
The current loss of biodiversity has been broadly acknowledged as the main cause of ecosystem change. To halt this trend, several international agreements have been made, and various biodiversity metrics have been developed to evaluate whether the targets of these agreements are being met. The process of developing good indicators is not trivial. Indicators should be able to synthesize and communicate our current knowledge, but they also need to meet both scientific and practical criteria. Since it would not be practical to monitor all species, indicators are mainly built on the monitoring of some well-known taxa, such as birds. Here we systematically review the wide spectrum of bird biodiversity indicators (hereafter indicators) available to: i) evaluate recent methodological advances; ii) identify current knowledge gaps jeopardizing indicator interpretation and use in guiding decision-making; and iii) examine challenges in their applicability across different spatial and temporal contexts. We pay particular attention to indicator characteristics such as site and species selection, spatial, seasonal and habitat coverage, and statistical issues in developing indicators and tools to tackle them, to provide specific recommendations for the future construction of indicators. Several methodological advances have recently been made to enhance the process of indicator development, including multiple ways to select sites and species to increase their robustness. However, we found that there are strong spatial, seasonal and habitat biases among the selected indicators. Most of them are from Europe, using mainly census data from the breeding season and typically covering farmland and forest habitats. The major challenges that we detected in their applicability were related to the modelling of the statistical uncertainty associated to the indicator. We recommend the use of quantitative methods in site and species selection procedures whenever possible. Current indicators should be expanded to areas outside Europe and to less studied habitats and should not neglect monitoring work outside the breeding season. Time-series analyses studying temporal trends and using multi-species data should in general account for temporal autocorrelation as well as for phylogenetic correlation. Multi-species hierarchical models are a good alternative for analysing and constructing indicators, but they need to include annual random effects allowing for unexplained annual variation in the average status of the community, i.e. the indicator target. Despite methodological and context-specific differences in the indicators reviewed, most of them seem to highlight the urgent need of devising strategic climate and conservation policies to improve the status and trends of biodiversity.
In Europe only some small isolated patches of forests with a high degree of naturalness still exist. These are forests, whose structure, composition and function has been shaped by natural dynamics without substantial anthropogenic influence over the long period. In this respect, Białowieża Forest is a unique location in Europe, with continuous forest cover for close to 12,000 years. The palynological, archaeological and historical data document only a weak anthropogenic fingerprint compared to other European lowland forests in Holocene history. Due to long-lasting protection, a large portion of the forest is still composed of stands originating from the pre-silvicultural period. Moreover, the stands of Białowieża Forest converted by silvicultural activities during the 20th century have the potential to recover owing to patches of stands with high naturalness, scattered throughout the forest. As conflict over management of the forest has recurred regularly for close to century, there is a need to summarize our knowledge on the forest history and natural assets, to help making scientifically informed decisions over its future. Expansion of a non-intervention approach to the Polish part of the forest is suggested to increase the stability of the entire ecosystem and enhance the chances for its successful adaptation to changing environmental conditions. This will increase the importance of Białowieża Forest as an open-door laboratory for biology, ecology, and forestry.
Long-term time series are necessary to better understand population dynamics, assess species’ conservation status, and make management decisions. However, population data are often expensive, requiring a lot of time and resources. What is the minimum population time series length required to detect significant trends in abundance? I first present an overview of the theory and past work that has tried to address this question. As a test of these approaches, I then examine 822 populations of vertebrate species. I show that 72% of time series required at least 10 years of continuous monitoring in order to achieve a high level of statistical power. However, the large variability between populations casts doubt on commonly used simple rules of thumb, such as those employed by the IUCN Red List. I argue that statistical power needs to be considered more often in monitoring programs. Short time series are likely underpowered and potentially misleading.
Predation, one of the most dramatic interactions in animals' lives, has long fascinated ecologists.
This volume presents carnivores, raptors and their prey in the complicated net of interrelationships, and shows them against the background of their biotic and abiotic settings. It is based on long-term research conducted in the best preserved woodland of Europe's temperate zone. The role of predation, whether limiting or regulating prey (ungulate, rodent, shrew, bird, and amphibian) populations, is quantified and compared to parts played by other factors: climate, food resources for prey, and availability of other potential resources for predators.
As the contribution for long-term ecological and environmental studies (LTEES) to our understanding of how species and ecosystems respond to a changing global climate becomes more urgent, the relative number and investment in LTEES are declining. To assess the value of LTEES to advancing the field of ecology, we evaluated relationships between citation rates and study duration, as well as the representation of LTEES with the impact factors of 15 ecological journals. We found that the proportionate representation of LTEES increases with journal impact factor and that the positive relationship between citation rate and study duration is stronger as journal impact factor increases. We also found that the representation of LTEES in reports written to inform policy was greater than their representation in the ecological literature and that their authors particularly valued LTEES. We conclude that the relative investment in LTEES by ecologists and funders should be seriously reconsidered for advancing ecology and its contribution to informing environmental policy.
The Ecology of birds can clearly serve as an indicator of climate and global change. Almost all aspects in the life cycle of birds, that have been regarded so far, show recent changes that can be linked to environmental changes. It is not surprising that birds show a high potential to adapt even complex behavior such as breeding or migration to changing environments-either through evolutionary mechanisms acting on the genetic basis of behavior or through available phenotypic plasticity. A high degree of agility and mobility might have helped birds to adapt better to new conditions than other organisms might have done. This is not to say that there is no conservation concern behind the reactions of birds to climate change. It is very likely that among bird species there will be winners and losers resulting from the current climate and global change and it might also be that the rate of losers will be high and extinctions of bird species will reach a level exceeding extinction rates seen in earlier times in bird's evolution. It is important to note that not all changes in bird behavior, as they are currently observed, can be attributed to climate change. Other factors, such as changes in land use, can influence the migration behavior of birds. Since birds are easy to observe, are present in all parts of the world, and are objects of interest to many people, they are ideal flagships to observe the consequences, and the impacts of future environmental changes on organisms and on ecosystems.
The number of small passerine bird territories was determined annually during 57 years (1953-2009) in a 13 ha broadleaf deciduous wood with several grazed glades, surrounded by crop farmland in southernmost Sweden. Only marginal habitat changes occurred. Both number of species and number of territories increased. Resident species and short-distance migrants tended to increase whereas tropical migrants declined. Many of the changes were similar to trends recorded by the national Breeding Bird Survey, suggesting that they were due to regional population trends. Notable changes were: former dominant Willow Warbler now rare but closely related newcomer Chiffchaff now well established, Garden Warblers replaced by Blackcaps, Tree Pipit strong recent decline, increase of cavity-nesting Great and Blue Tits, locally extinct Yellowhammer recovered. Species turnover between adjacent pair of years was without trend but turnover increased with increasing distance between pair of years predicting complete turnover by about 2190. A comparison with a larger oldgrowth wood nearby indicated no obvious effects of the small size and narrow configuration of the study site on its community.
We documented the composition and structure of the breeding bird assemblage in the primeval temperate
forest of the Białowieża National Park (BNP), during 2010-2014, and used 40 years of data to assess patterns of its diversity.
We applied an improved version of the mapping technique (a combined mapping method) for forest birds in seven
plots located in three old-growth forest types: ash-alder riverine, oak-hornbeam, and mixed coniferous. The composition
of the breeding avifauna and species richness remained basically unchanged. Jointly 67 (79% of 40-year total)
breeding species were recorded in 2010–2014. Overall 49 (57%) of all species bred in the study plots in more than 35
years, they formed c. 97% of the pairs in the breeding assemblage. The composition of the group of dominants changed
slightly; Phylloscopus sibilatrix became much less numerous in comparison to the earlier periods. Anthus trivialis ceased
to breed — possibly due to disappearance of its habitat. The numbers of Sylvia atricapilla reached the highest ever level,
and those of Columba palumbus and Dendrocopos medius equalled the maxima observed during 40 years. The overall
breeding densities did not change significantly but they were substantially lower than in the peak year (2001). Crown
insectivores, crown nesters and short-distance migrants remained the most numerous foraging, nesting and migratory
groups, respectively. The earlier observed density gradient across habitats – highest in the riverine, lowest in the coniferous
stands – was retained. Overall composition of the breeding avifauna did not change during 40 years, and no colonization
of forest areas by a new species, nor extinction of a formerly widespread species, except A. trivialis, were
observed. Some local changes of species richness occurred, however. Large-scale changes in coniferous habitats due to
die-back of Picea abies and appearance of canopy gaps were followed by the increase in species richness there, while disappearance
of former sharp forest edges reduced the number of species breeding in the “edge” plots. We suggest that
the high constancy of species composition of the breeding bird assemblage in BNP results largely from the interplay of
two factors: 1) long-term stability of the forest habitats, causing places suitable in one year to remain so over many seasons,
and 2) cross-generational reproducibility of the selection criteria used by the birds in their settlement decisions.
Overall bird densities ranged from 27.4 pairs/10 ha in coniferous to 105.5 p/10 ha in the forest-edge ash-alder stands, with the most frequent values between 50-70 (chiefly in oak-hornbeam stands). The densities of most species did not exceed 3 p/10 ha. Density of hole-nesters was surprisingly low (4.6 in coniferous, 22.3 in oak-hornbeam, and up to 36.2 p/10 ha in riverside forest-edge stands). The structure of bird assemblages was rather similar among various habitats and stable between years. Analysis suggests only a weak correlation between bird densities and food resources available during the breeding season. Very low breeding densities are tentatively explained as a result of an undersaturation of habitats by several bird species and, for those that saturate habitats, by low densities being an adaptation to heavy predatory pressure. -from Authors
Capsule Great Tits breeding in natural cavities in a primeval forest occupied microhabitats containing larger trees, but small differences between ‘breeding’ and ‘non-breeding’ locations indicated the minor importance of microhabitat selection in nest-placement decisions.Aims We tested whether Great Tits breeding in primeval conditions used vegetation composition to choose breeding patches.Methods Great Tit territories and nest-trees were mapped in two study areas in deciduous, old-growth forest. We compared tree species composition, tree girth and condition between ‘breeding’ and ‘non-breeding’ plots.Results Great Tit territories were tightly packed, filling most of the available area. Vegetation composition in ‘breeding’ and ‘non-breeding’ plots differed only for trees that could potentially harbour Great Tit nest-cavities; ‘breeding’ plots contained larger trees. The distribution of Great Tit nests varied between years, with some ‘non-breeding’ patches in one year becoming ‘breeding’ ones in another.Conclusion It seems unlikely that nest-placement decisions by Great Tits are constrained by the microhabitat quality under primeval conditions.
We examined the effects of different intensities of forest management practices
on bird communities in the Bialowieza Forest, eastern Poland. Stands
managed for more than 100 years (cutting, planting, removal of dead wood)
and stands that were partially protected in nature reserves (sporadic sanitary
cutting, removal of dead wood until 2008) were compared with unmanaged
stands in the Bialowieza National Park by surveying the bird community during
three breeding seasons (2010-2012). Surveys were conducted within three forest
habitats: spruce-pine (Pino-Quercetum), lime-hornbeam (Tilio-Carpinetum)
and ash-alder (Fraxino-Alnetum). Results showed that habitat structure
significantly affected the avian community. The basal area of live trees had a
positive effect on abundance of birds, while the density of live trees had negative
significant effect on bird abundance and species diversity. We also found
significantly lower abundance of insectivorous birds and cavity-nesters in managed
compared with unmanaged stands. Birds’ assembly in the spruce-pine
and ash-alder stands were most sensitive to management. These results show
that management can be used to sustain bird communities, including species of
conservation concern.
Numerous anthropogenic activities threaten the biodiversity found on earth. Because all ecological communities constantly experience temporal turnover due to natural processes, it is important to distinguish between change due to anthropogenic impact and the underlying natural rate of change. In this study, we used data sets on breeding bird communities that covered at least 20 consecutive years, from a variety of terrestrial ecosystems, to address two main questions. (1) How fast does the composition of bird communities change over time, and can we identify a baseline of natural change that distinguishes primeval systems from systems experiencing varying degrees of human impact? (2) How do patterns of temporal variation in composition vary among bird communities in ecosystems with different anthropogenic impacts? Time lag analysis (TLA) showed a pattern of increasing rate of temporal compositional change from large-scale primeval systems to disturbed and protected systems to distinctly successional systems. TLA slopes of <0.04 were typical for breeding bird communities with natural turnover, while communities subjected to anthropogenic impact were characterised by TLA slopes of >0.04. Most of the temporal variability of breeding bird communities was explained by slow changes occurring over decades, regardless of the intensity of human impact. In most of the time series, medium- and short-wave periodicity was not detected, with the exception of breeding bird communities subjected to periodic pulses (e.g. caterpillar outbreaks causing food resource peaks).
Large carnivores can either directly infuence ungulate populations or indirectly afect their behaviour. Knowledge from European systems, in contrast to North American systems, on how this might lead to cascading efects on lower trophic levels is virtually absent. We studied whether wolves Canis lupus via density-mediated and behaviorally-mediated efects on their ungulate prey species infuence patterns of browsing and tree regeneration inside the Białowieża National Park, Poland. Browsing intensity of tree saplings (height class 150 cm), irrespective of tree species or forest type, was lower inside a wolf core area (50.5%) where predator presence is highest, than in the remainder of the wolf pack’s home range
(58.3%). Additionally, browsing intensity was reduced when the amount of coarse woody debris (CWD), which can act as a ‘ungulate escape impediment’, increased (within 5-m radius) inside the wolf core area. No relationship existed outside the core area. As a result, the proportion of trees growing out of herbivore control increased more strongly with increasing amount of CWD inside compared to outside the wolf core area. Tis suggests that next to direct efects of wolves on ungulate density caused by a higher predation pressure inside the core area, risk efects are important and are enhanced by habitat characteristics. Tese results indicate that behaviorally-mediated efects of predators on prey can become more important than density-mediated efects in afecting lower trophic levels. Tis is the frst study we are aware of, that shows CWD can create fne-scale risk efects on ungulates with the potential for cascading efects of large predators on patterns of tree regeneration for a European forest system. Tis knowledge broadens the discussion
on how the impact of large predators on ecosystem functioning depends on the physical landscape, by illustrating these efects for a system which largely contrasts in this respect to the North American systems.
We investigated evidence for climate warming in the primeval forest of Bialowieza National Park (E Poland) over the last 33 yr (1975-2007). We examined whether local populations of 4 sedentary birds (Sitta europaea, Poecile palustris, Cyanistes caeruleus, Parus major) advanced their breeding phenology during that time, and how breeding phenology was affected by temperature variation during the period preceding egg laying. Mean yearly temperatures varied strongly across years, with a significant warming (similar to 1 degrees C) trend. Spring temperatures increased significantly solely in the second half of April. Only R major, which breeds later than the other species, showed a significant advance (similar to 9 d) in breeding. Breeding dates of S. europaea and P. palustris, which usually lay eggs before mid-April, did not significantly change over time. In all species, the onset of breeding was very variable across years (up to 30 d), as birds started breeding earlier in springs with higher temperatures in the pre-laying period. Such a wide range of phenological plasticity indicates that the birds already possess mechanisms enabling them to accelerate breeding in response to climate warming, provided that warming occurs in the pre-laying period. All species shifted their laying dates concurrently; thus, the order of egg laying (S. europaea, P. palustris, C. caeruleus, P. major) was retained irrespective of the spring earliness. This also indicates that mechanisms allowing birds to respond to their changing environments exist at the community level.
This paper documents data on standing dead trees (snags) in the pine-spruce (Norway spruce Picea abies, Scots pine Pinus sylvestris) natural stand in Bialowieza National Park (BNP) in northeast Poland. Trophically, this mostly coniferous stand represents one of the poorest habitats of the BNP, and this stand has never been cut. There are few tree species of significance, i.e., Scots pine, Norway spruce, hornbeam Carpinus betulus and two birch species Betula verrucosa, B. pubescens. Other tree species are scarce. Altogether 6.25 ha were measured within 25 samples. Among tree species, the proportion of dead standing trees was 0-58 percent of the total basal area and 0.9-59 percent of total density. The tree species dominance pattern shows a different pattern of change. Pine is declining, while hornbeam is invading the stand from bordering deciduous stands and now is a well regenerating tree species. Spruce regeneration slowed within the last 20 years. Until about 10 years ago, birches were not regenerating and were declining from the plot. Recently, within no more than the last 10 years, birches are regenerating within the plot again. All these changes reflect snag characteristics and composition.
The territory mapping technique censuses of the Collared Flycatcher F. albicollis were conducted on 25.5 ha plot in the Białowieża National Park. Conducted at the same time within the same plot, an intensive study on the ecology of the Collared Flycatcher allowed us to precisely assess the true number of breeding pairs (all nests were found). The combined version of mapping technique yields numbers which are an average 67% (min. 54, max. 92%) of the true numbers of the F. albicollis breeding pairs. This underestimation is negatively related both to the breeding losses in the Collared Flycatcher (r = -0.87, p = 0.010) and to its breeding density (r = -0.64, p = 0.125). Despite this underestimation the year-to-year changes in numbers obtained by both methods are positively correlated and highly significant (r = 0.84, p = 0.017). After an arithmetical formula was applied (i.e. 1.82* mapping result - 7.33) only an average 14% of bias occurred.
The 1995–1999 results of the mapping technique censuses carried out in permanent plots situated in
three types of old-growth primeval BNP stands (ash-alder riverine, oak-hornbeam, mixed coniferous) are
presented and contrasted with the data gathered in the same plots in the late 1970s. Most community parameters,
such as composition of breeding avifauna, species richness, make-up and cumulative proportion of dominants,
remained basically unchanged. Only the overall bird density has increased considerably, by 13–38% in different
plots. This has been due to parallel increases in numbers of several species, widely differing in their nesting sites,
food requirements and migratory habits. As numbers increased simultaneously in all the plots, the density
differences across habitats remained the same, from highest densities in riverine stands at the forest edge (up to
124 p/10 ha), through oak-hornbeam stands, to lowest in the coniferous stands (48–50 p/10 ha). Despite this
differentiation the breeding avifauna in individual plots was quite similar (density similarity index exceeding
50%), indicating that their breeding assemblages constituted samples from a single bird community. In most cases
the numerical increases could not be attributed to changes in local environmental factors, such as food resources,
weather conditions or changes in habitat structure. Only in the coniferous stands, could habitat changes leading
to diversification of their structure (gap formation, increasing number of deciduous trees) have been responsible
for increasing species richness and abundance there. The apparent lack of a relationship between changes in bird
numbers and the local situation suggests that the factors acting on a larger scale (outside the study area) could
have been involved. Despite the directional changes in bird abundance observed in the Białowieża Forest, its
breeding bird assemblage, when compared with amplitude of changes recorded over the same period in other
areas and habitats, stands out as an example of remarkable stability.
The 2000–2004 results of the mapping technique censuses carried out in permanent plots situated in three
types of old-growth primeval BNP stands (ash-alder riverine, oak-hornbeam, mixed coniferous) are presented and compared with data gathered in the same plots in the late 1990s. These data supplement earlier observations in the BNP and extend the long-term set of data on the breeding bird numbers there to a 30-year uninterrupted series (1975–2004). Most community parameters, such as the composition of breeding avifauna, the species richness, and the make-up and cumulative share of dominants, have remained basically unchanged. The overall bird density has increased by 8–20% in different plots; in 2001 it reached the highest level within the 30-year study period. The increase was due to parallel increases in numbers of several species, widely differing in their nesting sites, food requirements and migratory habits
— during this period 14 of the 26 most numerous species attained their highest numbers in the 30-year study period. Since numbers increased simultaneously in all the plots, the density differences across habitats remained the same, from the highest densities in riverine stands at the forest edge (up to 149 p/10 ha), through oak-hornbeam stands, to the lowest densities in the coniferous stands (54–56 p/10 ha). In most cases the numerical increases could not be attributed to changes in local environmental factors, such as food resources, or to detectable changes in habitat structure. The apparent lack of a relationship between the changes in bird numbers and the local situation suggests that factors acting on a larger scale (beyond the study area) could have been involved. Despite the directional changes in bird abundance observed in the Białowieża Forest, its breeding bird assemblage, when compared with the amplitude of changes recorded over the same period in other areas and habitats, stands out as an example of remarkable stability.
The composition and structure of the breeding bird assemblage in the Białowieża National Park (BNP) were documented in 2005-2009 and compared with the data from the previous 30 years. Mapping censuses were carried out in seven plots located in three forest types: ash-alder riverine, oak-hornbeam, and mixed coniferous forest. We checked whether the bird community composition had remained stable over the 35 years and the extent to which the numerical trends in BNP followed the regional trends. The composition of breeding avifauna and species richness was basically unchanged, except for the strongly increasing Sylvia atricapilla, which became a regular dominant in all habitats. The density gradient across habitats — highest in the riverine, lowest in the coniferous stands - was retained. After a maximum in 2001, the numbers of birds declined slightly, but densities were still among the highest in 35 years. Numbers of 18 of the 26 commonest species were higher in 2005-2009 than in 1975-2009; only Anthus trivialis, Phylloscopus sibilatrix, Ficedula parva showed negative trends, and Ficedula hypoleuca almost went extinct recently. Some numerical changes were attributable to local habitat changes (increases in Phylloscopus collybita and Sylvia atricapilla, declines in spruce-dependent species). Numbers of only four of 22 species (Dendrocopos major, Erithacus rubecula, S. atricapilla, Parus major) changed concurrently in BNP and the rest of Poland. The apparent lack of a relationship between changes in bird numbers and the local and regional situation suggests that factors acting on a far larger scale could have been involved. Despite these numerical changes, the breeding bird assemblage of primeval temperate forest stands out as an example of remarkable stability.
The influence of environmental and human factors on group sizes of large ungulates is still poorly understood, especially when considered at multiple timescales. We analyzed long-term data of red deer (Cervus elaphus) group sizes collected at 3 timescales in Białowieża Primeval Forest, Poland, from 1986 to 2003. On the daily scale, group size differed among periods of the day for females in summer (P = 0.001) and autumn (P = 0.04) but not winter (P = 0.18). Group size of males did not differ (P > 0.35) among the periods of day during any season. On the seasonal scale, both sexes had larger group sizes in winter than summer, and males were always more solitary than females. At the annual scale, multiple-regression analysis explained 96% (r2 = 0.957) of deer grouping patterns. Human hunting had the greatest influence (sr2i = 0.414), followed by acorn crop (sr2i = 0.012) and snow cover (sr2i = 0.008). Intense hunting by humans during a 5-year period appeared to cause increases in group sizes, even while red deer densities decreased. The disruption of the normally positive relationship of deer density to group size apparently affected predator–prey relationships, consequently red deer numbers continued to decline even after hunting pressure was relaxed. Our results indicate caution should be used when reducing red deer numbers by dramatic increases in hunting because the resulting behavioral and ecological changes in deer have implications that extend well beyond the season and year, with important consequences for the long-term stability of the population, especially in areas where large carnivores are present.
Capsule
European Starlings Sturnus vulgaris nested mostly in natural holes with strong walls (in live trees), typically excavated by medium-sized woodpeckers (small entrances, deep cavities), and high above the ground. Co-occurrence of these safety-enhancing features suggests that predation avoidance has been the main force shaping patterns of Starling nest site selection.
Aims
To describe patterns of nest site use by Starlings in a primeval forest and to assess the adaptive value of nest site choice.
Methods
Observations were made of Starlings breeding in undisturbed conditions in a strictly protected part of the Białowieża National Park, Poland. Intensive searches were made for nests (n = 2039) in permanent observation plots during 46 breeding seasons (1975–2020), coupled with measurements of hole attributes and observations of fate and re-use of nest sites.
Results
Starlings bred along forest edges in holes located in several species of deciduous tree; tree species used differed among habitats and hole location differed across tree species. The birds bred mostly in holes excavated by woodpeckers (70.3%), in trunks (77.4%) of living trees (84.5%). The median girth at breast height of these trees amounted to approximately 170 cm and median height of holes above the ground was 13 m. Starlings used holes excavated by the medium-sized woodpeckers roughly in proportion to their availability in the forest (tree species, stature, height above the ground). About 39% of holes were re-used in the consecutive years, with some holes being used over several decades.
Conclusion
The features of Starling nest holes (strong walls, narrow entrances, deep cavities) probably constitute adaptations to the need to evade predators. Their body size allows them to nest in excavated holes without threat of their broods being destroyed by woodpeckers.
The Natura 2000 network of protected sites is the pillar of biodiversity conservation in Europe. Although the Natura 2000 network directly addresses birds, these have shown worrying declining trends. It is therefore crucial to assess the potential contribution of Natura 2000 conservation measures. In this paper, we use a replicable method to model bird trends in the period 2000–2015 and the effects of Natura 2000 protection, across land cover classes, on regional abundances and local species richness and diversity. We model bird trends in Veneto, a North-Eastern Italian Region with areas among the richest in bird species in Italy. Bird data were derived from the national breeding bird monitoring scheme. Breeding birds showed declining trends at the regional level, confirming national and continental trends, particularly on agricultural and natural areas. The land cover class, rather than Natura 2000, mostly influenced population trends, however it was possible to observe slightly higher estimates of species richness and diversity in Natura 2000 sites. Despite the absolute higher estimates over the investigated period, farmland and woodland bird species had steeper declining trends inside Natura 2000 than outside, matching the values of diversity and richness of the areas outside the network at the end of the survey period. We conclude that the Natura 2000 network capacity to buffer biodiversity loss and act as a species-pool for non-protected areas is decreasing over time, mainly with regards to farmland and woodland birds. Natura 2000 implementation must be improved: management, monitoring and conservation measures should be better integrated into existing plans and funding should be made more efficiently available for Natura 2000 related expenditures.
Breeding birds were counted using point counts at 50 treefall gaps and 50 closed-canopy sites within one of the largest tracts of old-growth forest in Europe. Numbers of species and individuals were slightly, but significantly, higher at gaps. Overall bird species composition differed substantially at gaps and non-gaps. Dunnock (Prunella modularis), Blackcap (Sylvia atricapilla), and Chiffchaff (Phylloscopus collybita) were significantly more abundant at gaps. Wood Warbler (Phylloscopus sibilatrix) and Red-breasted Flycatcher (Ficedula parva) were significantly more abundant at non-gaps. Warblers (Sylviidae), ground insectivores, ground nesters, and short-distance migrants were significantly more abundant at gaps, but no species groups were more abundant at non-gaps. Eight species breeding in forest edges and young plantations in eastern Poland were not recorded in natural treefall gaps. The proportion of tropical migrant passerines was considerably higher in closed-canopy stands (0.47) than at gaps (0.29), which contrasts with the situation in most managed European forests where the highest proportions of tropical migrants typically occur in young-growth forests.
Long-term research in ecology and evolution (LTREE) is considered fundamental for understanding complex ecological and evolutionary dynamics. However, others have argued for revision of LTREE efforts given perceived limitations in current research priorities and approaches. Yet most arguments about the benefits and failings of LTREE could be argued to reflect the views of only the limited number of scientists who have authored reports on the field, and not the wider community of ecological and evolutionary scientists. To more systematically and quantitatively assess the views of the community on LTREE contributions and future activities, we conducted and here report the results of a survey of ecological and evolutionary scientists at primarily U.S.-based institutions, completed by 1,179 respondents. The survey objectives were to (1) identify and prioritize research questions that are important to address through long-term, ecological field experiments and (2) understand the role that these experiments might play in generating and applying ecological and evolutionary knowledge. Almost 80% (n = 936) of respondents said that long-term experiments had contributed “a great deal” to ecological understanding. Compared to other research approaches (e.g., short-term, single-site, modeling, or lab), there was overwhelming support that multi-site, long-term research was very important for advancing theory, and that both observational and experimental approaches were required. Respondents identified a wide range of research questions for LTREE to address. The most common topic was the impact of global change (n = 1,352), likely because these processes play out over many years, requiring LTREE approaches to fully understand. Another recurrent theme was the potential of LTREE approaches to build evolutionary understanding across all levels of ecological organization. Critical obstacles preventing some scientists from engaging in LTREE included short-term funding mechanisms and fewer publications, whereas the longer-term value for advancing knowledge and an individual's career were widely recognized. Substantive advances in understanding ecological and evolutionary dynamics then seem likely to be made through engagement in long-term observational and experimental research. However, wider engagement seems dependent on a more supportive research environment and funding structure, through increased institutional acknowledgement of the contributions of long-term research, and greater program support during the establishment and maintenance of research.
Birds as Monitors of Environmental Change looks at how bird populations are affected by pollutants, water quality, and other physical changes and how this scientific knowledge can help in predicting the effects of pollutants and other physical changes in the environment.
For more than 50 years, the Hubbard Brook Experimental Forest in the White Mountains of New Hampshire has been one of the most intensely studied landscapes on earth. This book highlights many of the important ecological findings amassed during the long-term research conducted there, and considers their regional, national, and global implications. Richard T. Holmes and Gene E. Likens, active members of the research team at Hubbard Brook since its beginnings, explain the scientific processes employed in the forest-turned-laboratory. They describe such important findings as the discovery of acid rain, ecological effects of forest management practices, and the causes of population change in forest birds, as well as how disturbance events, pests and pathogens, and a changing climate affect forest and associated aquatic ecosystems. The authors show how such long-term, place-based ecological studies are relevant for informing many national, regional, and local environmental issues, such as air pollution, water quality, ecosystem management, and conservation. © 2016 by Richard T. Holmes and Gene E. Likens. All rights reserved.
The first edition of this book has established itself as one of the leading references on generalized additive models (GAMs), and the only book on the topic to be introductory in nature with a wealth of practical examples and software implementation. It is self-contained, providing the necessary background in linear models, linear mixed models, and generalized linear models (GLMs), before presenting a balanced treatment of the theory and applications of GAMs and related models. The author bases his approach on a framework of penalized regression splines, and while firmly focused on the practical aspects of GAMs, discussions include fairly full explanations of the theory underlying the methods. Use of R software helps explain the theory and illustrates the practical application of the methodology. Each chapter contains an extensive set of exercises, with solutions in an appendix or in the book’s R data package gamair, to enable use as a course text or for self-study.
Analysis was conducted using the results of 15 mapping visits conducted by the author in 1992 in a 30-ha study plot in the oak forest in Moscow, Russia. During field work, special attention was paid to obtaining simultaneous records of singing birds. Within each of the four groups, the analysts showed a very high degree of mutual discrepancy. The coefficient of variation of estimates for 14 species varied from 21% to 87% among experienced analysts and from 45% to 90% among inexperienced ones. For each of 14 species, variation tended to be higher in the latter group. However, variances of estimates of experienced and inexperienced analysts differed significantly onlyt for one of 14 species. Proportions between species were similarly reflected by different persons. -from Author
In the Bialowieza National Park, E Poland, regular occurrence of polygyny in Phylloscopus sibilatrix, P. collybita and Troglodytes troglodytes was recorded. The polygynous males were usually bigamists. All females contained by a polygynous male settled in the same territory. Polygynous birds were recorded almost exclusively in optimal (= high-density) habitats. Proportion of polygynous males in these habitats varied considerably between years, ranging from 0-40%. Mating success of individual males also varied among seasons. Primary and secondary females settled often at the same time or only 1-2 days apart. Production of young per female in polygynous groups was not lower than the production of females mated to monogamous males. Current models dealing with female choice are insufficient to explain the evolution of polygyny because the settling females have to make a whole series of decisions; they have not only to choose mates but also habitats and geographical areas in which to breed. Monopolization of access to females by males can result in the appearance of polygyny even if it is detrimental to females. A model showing how differences in female and male habitat distribution (ideal free and ideal dominance, respectively) can lead to locally skewed sex ratios and occurrence of facultative polygyny, is presented. In order to explain the evolution of the resource defence polygyny one has to study simultaneously reproductive options available both to the females and to the males, as well as a whole set of ecological factors influencing the monopolizability of habitats by the males and costs of polygyny to the females. -from Author
Questions
Does the size structure characterizing particular tree species in natural forest stands converge towards a steady state? What is the main reason for departures of observed tree size distributions from equilibrium models? What is the consequence of long‐term strict protection for the demography of tree species and the conservation of associated biota?
Location
Stands of natural forest in Białowieża National Park (NE Poland) that have been under strict protection for about 90 yr.
Methods
Data on recruitment, growth and mortality of approximately 10 000 trees representing 11 species (aspen, birch, alder, pine, oak, maple, ash, elm, spruce, lime and hornbeam), from seven replicated surveys of five permanent monitoring plots (total size = 15.44 ha), established in 1936, were used to derive theoretical, species‐specific equilibrium distributions as a basis for evaluating the demographic changes of the species involved.
Results
Over a monitoring period of 76 yr, there were strong downward trends in the population densities of several tree species of different successional status and light requirements. A vast majority of the conspecific equilibrium curves, modelled on the basis of growth and mortality data, revealed a ‘rotated sigmoid’ shape when plotted in semi‐log plots. In contrast to these equilibrium curves, the observed tree size distributions of most species were unimodal, at both the beginning and the end of the study period. Departures between theoretical and observed distributions increased over time, particularly for shade‐intolerant and intermediate species.
Conclusions
The populations of several tree species occurring in the Białowieża National Park are demographically unstable – a fact reflected in large and steadily increasing differences between theoretical and actual tree size distributions. The main reason for this are the insufficient recruitment rates typical of most species. Some tree species may very soon disappear almost entirely, and this will certainly lead to far‐reaching changes in the functioning of local forest communities. Among other consequences, the current demographic trends, as observed for Białowieża tree species, are very likely to have a strong effect on the long‐term survival of numerous forest organisms (such as insects, fungi, lichens, etc.), which depend, directly or indirectly, on the presence and balanced demography of particular tree species.
As a result of some 500 years of protection, parts of the Białowieża Forest, in Poland, remain in a near-primeval condition. Studies of the breeding birds in the core part of the forest (Białowieża National Park) over 29 years show that the bird community is species-rich but that densities of individual species are usually low, resulting in only moderate overall densities. In some species, low densities are a consequence of large territories and social exclusion, but more often they reflect the undersaturation of habitats by birds, despite superabundant food supply and nest-sites. Low productivity, resulting from high nest predation, may contribute to undersaturation. Species composition and numbers of birds fluctuate within relatively narrow limits, with the populations of closely related species fluctuating either independently of one another or in parallel; interspecific competition for resources plays a minor role. Some attributes of the Białowieża ecosystems resemble conditions in undisturbed tropical forests but contrast sharply with those in fragmented, temperate secondary forests. The present Białowieża avifauna provides a glimpse of that existing in central European forests before their historical transformation by humans. Its present exceptional character arises from preservation of most of its pristine features. The forest constitutes a critical reference point for studies of woodland ecology, and its preservation should be a high priority. Unfortunately, commercial logging continues, gradually changing the forest's structure and affecting the birds, especially those dependent on dead wood and old-growth. The relatively small national park (47.5 km 2) is increasingly becoming an 'island', in which the long-term preservation of primeval forest features will be impossible.
Results of mapping censuses carried out in plots situated in three types of old-growth stands (riverine, oak-hornbeam, coniferous) in 1990-1994 are presented and contrasted with data gathered in the same plots in 1970s (Tomiałojć et al. 1984). Community composition parameters: number of breeding species (72 versus 75), make-up of dominants, and overall assemblage similarity (Renkonen's index 76-87%) remained basically unchanged. Total density did not change in swampy stands but increased by 20-40% in oak-hornbeam and coniferous habitats. These increases were most pronounced in crown and bark insectivores guilds (what could be partially due to three year outbreak of Geometridae caterpillars in 1990s), in hole nesters and open nesters in tree crowns. All migratory groups but tropical migrants increased in numbers. The latter group remained numerically stable. Ground nester numbers did not change in dry habitats but they decreased in swampy places, parallel with the decreased hydration of this habitat in 1990s. In coniferous plots, growing number of gaps and expansion of deciduous trees, resulted in enrichment of breeding avifauna and increase in mean number of breeding species there.
Numerical variation of the breeding bird community, its ecological subunits (guilds) and the 26 most numerous constituent species is analysed over 20 yr period (1975-1994), and related to variation in supply of defoliating caterpillars, tree seed crop, numbers of rodents and winter weather. Maximum rates of increase between two years were less than twofold in most species. Changes in numbers of individual species/guilds were either independent of each other or in parallel. The pattern of numerical variation was not related to taxonomic affinities, type of nest site, food types, or migratory habits. Whole bird community and 13 of 26 species showed long-term increasing trends, only three species declined. Numbers remained basically stable during the first decade, increases were concentrated to the second decade. Except tropical migrants (no long-term change) other migratory groups increased in numbers. None of the measured environmental variables showed parallel trends, which could account for the recorded trends. Long-term trends and year-to-year fluctuations were not correlated. The short-term variation in bird numbers was to some extent correlated with (in decreasing order of importance) abundance of defoliating caterpillars, winter severity, and changes in rodent numbers. No correlation with tree seed crop was found. Overall, a substantial part of the variation in breeding bird numbers could not be explained by that set of factors. This could be due to birds using wider spectrum of food sources than those measured, varying predator pressure and/or strong influences from outside the forest, swamping local relationships.
Counts of birds are used for many purposes in a variety of field studies. Simple presence-or-absence information suffices to study avian biogeography, but indices of abundance are needed to track the changing mix of species’ populations associated with plant succession. Still other studies, as of trophic dynamics, require knowledge of population densities. This chapter critically assesses the suitability of various counting methods for each of these purposes. It is not a thorough review of the topic. These have been provided already by Kendeigh (1944), Blondel (1969), Berthold (1976), and Dawson and Verner (in preparation); Robbins (1978) and Shields (1979) should also be consulted, although the scope of their reviews was less extensive.
Data on the location of 413 and dimensions of 198 Marsh Tit nesting holes gathered in 1975-95 in a strictly protected forest reserve are analysed. Breeding was confined to deciduous stands. In riverine stands over 96% of the holes were in Alnus and Fraxinus, in oak-hornbeam stands over 83% in Tilia and Carpinus. Holes were on average 5.6 m above the ground, in trees with girth at breast height 107 cm, both parameters varied strongly among tree species. Holes were situated mainly in tree trunks (89%), in living trees (92%), and the share of woodpecker-made holes was <2%. Entrances were mostly (74%) in vertical plane. Their minimum diameter was 20 mm in circular openings and 18 mm in elongated ones, median - 30 mm. Openings were usually elongated, in 65% of cases they were <20 cm 2. Hole bottoms were approximately circular, with median diameter of 9 cm, and minimum diameter of 5.5 cm, median bottom area was 73 cm 2. Depth of holes (to nest level, median 14 cm) was positively correlated with the least entrance diameter (r S = 0.48). In comparison with other areas Marsh Tits bred higher, in holes with larger bottoms, the holes having, however, similar depth and entrance diameter. None of the hole dimension variables depended on tree species, thus the observed variation in hole placement was probably to a large extent a by-product of differences in distribution of holes with adequate qualities. Small openings of holes could serve to avoid competition for holes and/or to evade predators, but non-usage of woodpecker-made holes and nesting in holes in living trees can be best explained as an anti-predator tactic.
Diversity patterns in eastern Nearctic and western Palaearctic temperate and boreal breeding assemblages of forest birds are compared. Several spatial scales of diversity were considered. First, the number of forest passerine species present in continental and regional (200 X 200 km(2)) pools were counted; secondly, average dissimilarities between breeding assemblages of passerine birds within a forest type (pine dominated forests) on a continent wide scale are calculated to assess the compositional variation among regional pools on each continent. Thirdly, the between-habitat diversity was assessed by comparing census results from two different forests types within regions. Finally, within-habitat diversity was measured by estimating the number of species present in standard samples from Nearctic and Palaearctic forests. Breeding assemblages of passerine birds of the eastern Nearctic region are more diverse than those of the western Palaearctic region on several spatial scales. First, there are more forest bird species in continental and in most regional species pools. Secondly, Neartic regional species pools are not only richer but also structurally more variable as revealed by a larger dissimilarity among Nearctic than Palaearctic pine forest bird assemblages. Thirdly, dissimilarity in bird community structure between two forest types is larger in the Nearctics, indicating a higher between-habitat diversity there. However, local breeding bird assemblages are about equally rich in species on both continents. The results match well with knowledge of the differences between the two continents in the history of avifaunas and vegetation formations. The results imply that conservation strategies should be uniquely tailored to local communities, taking into account the ecological characteristics of the species.
Wood warbler nests were studied in ash-alder, oak-hornbeam and coniferous stands in Bialowieza National Park, E Poland. Nests were built on the ground, usually in shaded places, generally hidden among low herb vegetation or wedged under branches. Most clutches were laid within a fortnight of the first eggs laid in the population. On average breeding started earliest in the oak-hornbeam and latest in the coniferous habitat. Few females attempted 2nd broods. First clutches usually contained 6-7 eggs. Average clutch size varied between years, declined over the season, and was highest in the most densely populated oak-hornbeam stands. The birds produced smaller clutches than the number of young which could be reared. Variation in clutch size is possibly an adaptation to changing food availability and variation in predation pressure, the maximum clutch size being limited by the size of the nests as well as by trade-offs between the amount of investment in one breeding attempt and the changes to reproduce again. On average >70% of nests were lost, one of the highest figures recorded in open nesting birds of the temperate zone. Predators were responsible for >80% of the losses. Nests with young were 4 times more likely to be predated than nests with eggs. Predation rates were independent of brood size, but late nests had higher rates of predation. Losses were lowest in the ash-alder stands and highest in the coniferous stands. Due to heavy predation, the yearly production of young per female was scarcely 1/3 of the potential production. Mortality of adults in the breeding season was estimated at 4.3% month -1 for females and 4.5% month -1 for males.-from Author
The common ash (Fraxinus excelsior L.) is threatened by a new disease which is currently spreading across Europe from east to west. The recently described anamorphic fungus, Chalara fraxinea Kow. is most likely playing a key role in this process, but the additional involvement of other factors (e.g. climate, insects) is possible. Based on observations in Poland, the authors describe the disease symptoms and the morphology of the fungus. In addition, the available literature on this epidemic is reviewed.
The rank-abundance distribution (RAD) represents the manner in which species divide resources. Community-specific division rules that determine resource allocation among species, and thereby the shape of the RAD, have been hypothesized to account for observed stability of local species richness over time. While the shape of the RAD has been well studied, the temporal dynamics of this distribution have received much less attention. Here we assess changes in the shape of the RAD through time in a desert rodent community in Arizona (USA). Because energy use may be more appropriate for studying resource division than abundance, we also evaluate an energetic equivalent of the RAD. Significant, directional trends in the shapes of both distributions are present in this community. These changes are driven by trends in the relative abundances (or energy use) of Ranks 2, 3, and 4, and are significantly correlated with variation in total energy use by the community and with compositional change. Our results suggest that (1) rank-abundance and rank-energy distributions are not static and can change directionally through time, (2) species richness and rank distributions are not necessarily as intimately connected as early studies assumed, and (3) rank-abundance and rank-energy distributions are influenced by both the amount of energy available to the community and species-specific interactions.
The accuracy of the territory-mapping technique for estimating the abundance of densely breeding Hawfinches was tested in an old and unfragmented lime-oak-hornbeam forest in the Białowieża National Park, E Poland. Hawfinch numbers estimated from counts of the whole bird community carried out with the application of the standards of the improved mapping technique were compared with seven-year data on the bird's true numbers, which are known from parallel intensive nest searches and persistent tracking of the movements of pairs. In a forest with a dense population of Hawfinches the mapping technique underestimated their numbers by 20% in years of moderate density and by 35% during high-density years. Even though the underestimation was negatively correlated with the true density of Hawfinches, the figures obtained by both methods reflected year-to-year changes in a similar way. An improvement in mapping data is achievable either by closer attention being paid to the species during standard visits (the best ones for surveying it), or post factum by the introduction of a correction factor into the mapping-technique figures.