Many forest specialist birds are in widespread decline across Europe. In Britain, marsh tits are an indicator species of mature native woodlands, but have suffered an 81% population decline since the 1960s. We assessed whether habitat degradation during the mid 20th century, through the widespread conversion of native deciduous woodland to conifer plantations, could have impacted marsh tit populations. We surveyed the recent number of occupied marsh tit territories in 74 discrete woodland patches (‘woods') of 1–296 ha in England, comprising purely native deciduous woodland or with varying coverages of conifer plantations (0–89%). We found that the number of marsh tit territories increased with the woods' size, but this increase was significantly greater for deciduous woods, and lower for woods with a greater proportion of conifer plantation. The area of woodland in the local landscape, reflecting a wood's isolation, had no significant effect on marsh tit abundance in a focal wood. The results indicated that the historical conversion of native deciduous woodland to conifer plantation likely degraded a substantial proportion of formerly high‐quality habitat for marsh tits, affecting up to 37.3% of potentially suitable woods and possibly one‐fifth of the former marsh tit population directly, likely contributing to the species' national decline. Many of the larger coniferized woodlands are in public/state ownership, which could facilitate habitat restoration for the conservation of woodland specialists, like marsh tits, via centralized policies, with additional incentives targeted at woodlands in private ownership. We cautiously estimated that restoration of native woodland could re‐establish a median of 24 610 marsh tit territories in Britain, equivalent to an additional 86% of the current national population.

1. Nests built by vertebrates constitute diverse microhabitats that are inhabited by many taxa other than their owners. Hence, vertebrate nests can be important hubs of local biodiversity. 2. Arthropods are the largest group of additional nest users, forming complex networks of interspecific relationships; hence, the distribution of nest-building animals and the availability of their nests may have a significant impact on local arthropod communities. 3. We investigated factors that may explain differences in macroarthropod communities in ephemeral nests of Wood Warblers, Phylloscopus sibilatrix (Bechstein, 1793), a declining ground-nesting songbird, and compared them to leaf litter nearby. 4. In 2019-2020, we collected 168 warbler nests and 45 leaf litter samples in the primeval stands of the Bialowieza Forest (Poland). From nests and litter samples, we extracted, respectively, 11759 and 349 macroarthropod specimens, which represented 183 and 70 species. 5. The composition of nest-dwelling macroarthropods varied within and between years, and between the warbler's nesting stages, and with time since nest abandonment by the birds. Habitat type, nest size and material composition poorly explained differences in the nests' macroarthropod communities. Compared to leaf litter in the surrounding environment, warbler nests hosted distinctive, more abundant and slightly more diverse macroarthropod communities. 6. Our findings are likely to be relevant to a wide range of bird and mammal nests. Thus, the widespread decline of nest-building vertebrates might reduce the availability of nest resources, potentially posing a previously overlooked threat to invertebrate conservation.

Insectivorous, Afro-Palearctic migrant birds provide cross-border ecosystem services, but many are declining rapidly. The complex life cycle of migrant birds makes their conservation difficult, but understanding where they spend time during the breeding season can help indicate where those actions will be most effective. We used the spotted flycatcher (Muscicapa striata), a declining, Afro-Palearctic, migratory insectivore and habitat generalist, as a model to examine how river density and land-cover change were associated with loss and colonization during the breeding season of 2 × 2-km national atlas survey areas from 1990 to 2010. Greater river density was associated with a lower probability of loss (odds ratio [OR] 0.8) between survey periods and a higher probability of colonization (OR 1.25). Loss was associated with increases in urban land cover (OR 1.17), and, unexpectedly, colonization was negatively associated with increases in woodland (OR 0.91) and standing freshwater (OR 0.94). Our results suggest that habitat creation is unlikely to provide sufficient benefits for some insectivorous birds within the time needed for population recovery. Thus, efforts should focus on the protection and improvement of established habitats. River density was strongly associated with the persistence of the spotted flycatcher, and this finding highlights that understanding the benefits of freshwater habitat for terrestrial species should be a priority for conservation management.

Rewilding initiatives are increasing in number across Europe and the UK in response to a growing awareness of substantial nature depletion, despite a lack of policy, guidance and legislation. Ongoing transformations of UK environmental policies offer a ‘policy window’ in which rewilding could become established as a key strategy for nature recovery. Here, we present the results of discussion sessions held as part of a British Ecological Society Policy Training workshop. A total of 46 participants, academics, practitioners and young people interested in rewilding attended. Our discussion focused on three pre‐determined thematic discussion sessions: (1) barriers to rewilding and trade‐offs; (2) species reintroductions; (3) facilitating rewilding in policy. Using thematic analysis, four emerging cross‐cutting themes were identified from our workshop discussions: (a) environmental stewardship & public engagement, (b) cross‐policy approaches, (c) incentivising rewilding and (d) an evidence base for rewilding. Policy Implications . Given the UK's considerable biodiversity loss, restoring ecosystem processes and function on a large scale is increasingly urgent, and operationalising rewilding through supportive environmental policy structures should be a key priority for government. Read the free Plain Language Summary for this article on the Journal blog.

Effective conservation of biodiversity requires a good understanding of ecosystem dynamics in response to natural and anthropogenic influences. Long-term studies (LTS) conducted over multiple decades provide essential insights into ecological processes and interactions over time, which can inform conservation strategies, but they are anchored within their wider society and geopolitics. The context of any LTS is therefore vulnerable to temporal instability, including disruptions and challenges but also scientific opportunities. The resilience and adaptability of LTS in the face of political, social or environmental change is key to their continuity and relevance for science and society. Poland's iconic Bia & lstrok;owiez(center dot)a Forest hosts unique remnants of European old-growth forest, and also diverse LTS lasting up to nine decades, revealing a dynamic ecosystem. The Bia & lstrok;owiez(center dot)a Forest is a hub of international science, providing an essential reference for ecosystem functioning and evolutionary processes, and a key benchmark for wider perceptions of 'natural forest', which is increasingly relevant to ecological restoration elsewhere. Nevertheless, the Bia & lstrok;owiez(center dot)a LTS have persisted against a backdrop of profound sociopolitical and geopolitical change, which has challenged their scope and viability. The Bia & lstrok;owiez(center dot)a experience has a wider resonance for LTS in other regions, because change can affect science anywhere, even in situations that currently appear stable. We describe how Bia & lstrok;owiez(center dot)a's LTS have maintained continuity and relevance for our understanding of forest ecosystems by embedding core expertise among diverse institutions, building collaborative teams around visionary leaders and dispersing risks of financial, political and security vulnerabilities. However, issues remain around centralised data archiving and availability. These perspectives provide general lessons for supporting LTS in a changeable world.

Cross-system fluxes of aquatic insects rich in omega-3 long-chain polyunsaturated fatty acids (ω-3 LC-PUFAs), specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may subsidise insectivorous vertebrates that are suffering due to terrestrial insect declines. The benefits of high ω-3 LC-PUFA diets, such as improved growth and immunocompetence, have previously been demonstrated for riparian insectivores. Understanding the potential for aquatic insects to benefit a range of species is necessary for informing land management practices. Using the spotted flycatcher (Muscicapa striata), a habitat-generalist, insectivorous bird as a model, we tested how blood plasma ω-3 LC-PUFA concentrations and the ratio of ω-6:ω-3 fatty acids were related to the body condition of 14 adults and 84 chicks in the wild. We measured how variation in ω-3 LC-PUFAs and ω-6:ω-3 was related to river proximity, to test whether they were related to aquatic insect availability. We assessed how these relationships may extend beyond the individual level by monitoring flying insect availability throughout two breeding seasons and testing its ability to predict reproductive success. EPA was positively correlated with body condition in chicks and adults and declined with distance from a river. Conversely, ω-6:ω-3 was negatively correlated with body condition and increased with distance from a river. Breeding success was positively correlated with aquatic insect availability, suggesting that access to a high ω-3 LC-PUFA diet has the potential to mitigate declines in generalist insectivores. Our results highlight how the maintenance or creation of high-quality freshwater habitats may be promoted in a conservation context for non-riparian species.

Hedgerows and other woody linear features (WLF) are important semi-natural habitats, cultural features and potential carbon stores in farmland across several regions of the world, particularly Western Europe. Monitoring WLF has been limited by difficulties of mapping their extent and dimensions at large scales. Remote sensing can overcome such limitations by mapping WLF at high resolution at the national scale, but examples are few and generally more localized. We tested whether openly available, 1 m2 resolution lidar could be used within a high-performance computing environment to model the extent and height of the WLF coverage in England. The results were compared with comprehensive ground truthing within 248 × 1 km2 sample squares. There was close agreement (99.7 %) between the mean and total extent of WLF from the model and ground truthing squares, with 74 % of modelled WLF showing close alignment (<20 m distance) with ground truthed WLF. Total length of WLF in England was estimated as 641,079.8 km, with 29 % composed of trees/bushes taller than 6 m, and 61 % (389,439.3 km) corresponding to managed hedgerows of 1-6 m tall. Precise agreement between height classes in the model and sample squares was more modest (36 % of WLF lengths), but higher (60 %) if allowing a tolerance of ±1 height class for matching to accommodate temporal differences between lidar collection (2016-2021) and ground truthing (2022-2023). The model represents a significant improvement in mapping and monitoring WLF using openly available national lidar, and the limitations and potential opportunities are discussed.

1.Creating woodlands through natural processes, as opposed to traditional tree planting, is expected to result in more structurally diverse, locally adapted woodlands that enhance the resilience of existing treescapes. However, the outcomes of natural colonisation can be variable, and there is still considerable uncertainty around the ecological processes involved. 2.To address knowledge gaps and guide a future research and policy agenda, we synthesise current knowledge of the ecology of natural colonisation in Great Britain. We combine expertise from 31 practitioners and researchers spanning varied British contexts, including insights from 15 case studies and an expert survey on the relative importance of ecological factors influencing natural colonisation. 3.The most important determinants of successful natural colonisation, identified by practitioners and researchers, were the availability of seed sources and low levels of herbivory. However, key knowledge gaps remain around the timeframe and trajectory of woodland development and appropriate management practices. Natural colonisation and tree planting can be combined to meet diverse woodland objectives, but this has been little explored to date. 4.Solutions. Land managers and advisors face uncertainty and many knowledge gaps when creating woodland through natural processes. Site monitoring and adaptive management can help meet site objectives that, in turn, can be supported by policies reflecting uncertainties in the process. Collaboration between researchers and land managers to monitor woodland development, use experimental approaches and share knowledge will help further applied ecological understanding, supporting informed decision-making by land managers.

Context Land-use change is a key driver of biodiversity loss. Models that accurately predict how biodiversity might be affected by land-use changes are urgently needed, to help avoid further negative impacts and inform landscape-scale restoration projects. To be effective, such models must balance model realism with computational tractability and must represent the different habitat and connectivity requirements of multiple species. Objectives We explored the extent to which process-based modelling might fulfil this role, examining feasibility for different taxa and potential for informing real-world decision-making. Methods We developed a family of process-based models (*4pop) that simulate landscape use by birds, bats, reptiles and amphibians, derived from the well-established poll4pop model (designed to simulate bee populations). Given landcover data, the models predict spatially-explicit relative abundance by simulating optimal home-range foraging, reproduction, dispersal of offspring and mortality. The models were co-developed by researchers, conservation NGOs and volunteer surveyors, parameterised using literature data and expert opinion, and validated against observational datasets collected across Great Britain. Results The models were able to simulate habitat specialists, generalists, and species requiring access to multiple habitats for different types of resources (e.g. breeding vs foraging). We identified model refinements required for some taxa and considerations for modelling further species/groups. Conclusions We suggest process-based models that integrate multiple forms of knowledge can assist biodiversity-inclusive decision-making by predicting habitat use throughout the year, expanding the range of species that can be modelled, and enabling decision-makers to better account for landscape context and habitat configuration effects on population persistence.

Human activity has modified the availability of natural resources and the abundance of species that rely on them, potentially changing interspecific competition dynamics. Here, we use large-scale automated data collection to quantify spatio-temporal competition among species with contrasting population trends. We focus on the spatial and temporal foraging behaviour of subordinate marsh tits Poecile palustris among groups of socially and numerically dominant blue tits Cyanistes caeruleus and great tits Parus major. The three species exploit similar food resources in mixed groups during autumn-winter. Using 421 077 winter recordings of individually marked birds at 65 automated feeding stations in Wytham Woods (Oxfordshire, UK), we found that marsh tits were less likely to join larger groups of heterospecifics, and they accessed food less frequently in larger groups than in smaller ones. Marsh tit numbers within groups declined throughout the diurnal and winter periods, while the number of blue and great tits increased. However, sites that attracted larger groups of these heterospecifics also attracted more marsh tits. The results suggest that subordinate species exhibit temporal avoidance of socially and numerically dominant heterospecifics, but have limited ability for spatial avoidance, indicating that behavioural plasticity enables only a partial reduction of interspecific competition.

Due to specific microclimatic conditions and accumulation of organic matter, bird nests are microhabitats that are often inhabited by various invertebrates, including mites (Acari). We tested whether nests of the ground-nesting passerine Phylloscopus sibilatrix (Bechstein) (Passeriformes: Phylloscopidae) [wood warbler] were associated with an increased local diversity of ptyctimous mites (Acari: Oribatida) on the forest floor in the Białowieża National Park, East Poland. In 2019–2020, we analysed 150 warbler nests shortly after they had been vacated by the birds, and additionally we sampled mites in leaf litter at 1 and 6 m distances from 21 of the collected nests. We found on average more mite species in nests sampled in 2020 than in nests sampled in 2019. Although the species composition largely overlapped between bird nests and the litter, bird nests contained a greater average number of mite species than litter samples, including species found only – Microtritia minima (Berlese) and Phthiracarus crenophilus Willmann – or mostly – Euphthiracarus cribrarius (Berlese) and Phthiracarus globosus (C.L. Koch) – in bird nests. The results suggest that the presence of bird nests may increase the local diversity of the invertebrate species assemblage.

Romilio (2021) used a taxonomic scoring system to compare differences between three species of geese (Anseriformes) depicted in the Chapel of Itet, one of which he speculated might represent an undescribed (presumably now extinct) species. Despite some apparently distinctive features, the depiction has traditionally been associated with the well-known modern species, red-breasted goose (Branta ruficollis). We discuss limitations in applying the Tobias et al. (2010) scoring system to cases such as this, for which it was not designed, and we outline the many pitfalls that must be considered when attempting to identify historical artwork of birds using examples discussed recently in the ornithological literature. We conclude that the illustrations proposed by Romilio to represent a new Branta goose species are within the range of known plumage variation and potential artistic licence for red-breasted goose, and that this very probably is the species upon which the artwork was based. More generally, we caution against applying the Tobias criteria to cases where a series of specimens cannot be measured, and highlight the difficulties of using illustrations to inform taxonomy.

Abstract. Tree cavities are an essential resource for cavity-dwelling mammals, birds, invertebrates and fungi, and so are important for maintaining forest biodiversity. In North American forests, woodpeckers (Picidae) play a keystone role in cavity creation by excavating holes. However, in European forests many hole-nesting songbirds rely on non-excavated cavities that are formed by fungal decay and compartmentalization after tree damage. Several factors are recognised in initiating non-excavated cavities that are used by hole-nesting birds, including loss of a tree branch or stem breakage, but this topic is poorly studied. Here, we propose that bark stripping by large herbivores (e.g. Red Deer Cervus elaphus and European Bison Bison bonasus) could be another important, and previously overlooked, mechanism for initiating tree cavities that are used by hole-nesting birds. We suggest that, after the initial damage from herbivore bark-stripping, fungal decay can create specific elongated, slit-like cavities, which are particularly important as nest sites for some common forest songbirds. We outline this idea using original observations and evidence from the literature, primarily from the primeval forest in Poland's Białowieża National Park. We also use studies from elsewhere in Europe to show a generally low usage of slit cavities by birds where large herbivores are scarce or absent. We suggest that restoring such animals in European forests could help to restore the abundance and diversity of the tree cavity resource for hole-dwelling species. We encourage future research to investigate this proposal of large herbivores being important agents of tree cavity formation that could enhance biodiversity.

Weather has a dominant impact on organisms, including their life histories and interspecific interactions. Yet, for nesting birds, and the arthropods inhabiting bird nests, the direct and cascading effects of weather are poorly known. We explored the influence of ambient temperatures and rainfall on the cohabitation of dome-shaped bird nests by Wood Warblers Phylloscopus sibilatrix , their blowfly Protocalliphora azurea ectoparasites, and predatory Myrmica and Lasius ants that may provide nest sanitation. We sampled blowflies and ants in 129 nests, and measured warbler nestlings during 2018–2020 in the primeval Białowieża Forest, eastern Poland. The probability of ectoparasites occurring in nests increased with increasing ambient temperatures and declining precipitation in the early nestling stage, when adult blowflies are ovipositing. Where present, the number of ectoparasites was greater if higher ambient temperatures had prevailed in the late nestling stage, but only when ants were absent from nests. However, the nestling growth was unrelated to ectoparasite abundance or ant presence within bird nests, although it was lower at high rainfall. The results suggest that weather can have conflicting impacts on interactions between nesting birds and nest-dwelling arthropods, but birds can mostly compensate for any related costs in old-growth forest, where food is generally abundant.

Declines in farmland biodiversity remain evident despite over three decades of research and implementation of agri-environment schemes (AES). Although positive effects of AES are often demonstrated locally or in the short term, studies exploring longer term trends in biodiversity often show contradictory results. Evidence for the potential of AES to drive beneficial changes in populations remains sparse, especially for mobile taxa such as birds and butterflies. We analysed the abundance of 12 widespread bird and 9 butterfly species from a 10-year study of AES intervention in a farmland landscape in southern England. We compared estimates of annual population growth rates from our study landscape with rates derived from large-scale national monitoring schemes in equivalent landscapes without substantial AES. Species trends in our study landscape were frequently stable or increasing, in contrast to concurrent declining trends in equivalent landscapes without AES. These differences were significant for total abundance of granivorous species and for chaffinch Fringilla coelebs, blue tit Cyanistes caeruleus and great tit Parus major individually. For butterflies, differences in trends were significantly more positive for gatekeeper Pyronia tithonus and green-veined white Pieris napi, while small white P. rapae showed a trend that was significantly more negative in our study landscape. Synthesis and applications. Our results demonstrate that, for some bird and butterfly species, the higher abundances associated with areas of AES uptake within a typical commercial farmland landscape can co-occur with positive or stable population trends over long time scales and that these trends can show significant differences from those in equivalent landscapes without substantial AES interventions. Our results suggest that previously observed inconsistencies in AES benefits may in part reflect a lack of long-term studies with accurate data on AES uptake and quality (i.e. successful implementation and management). Our results, thus, affirm the importance of delivering and monitoring high-quality AES options if the design and implementation of the next generation of AES is to achieve significant benefits for biodiversity.

Passive rewilding is a potential tool for expanding woodland cover and restoring biodiversity by abandoning land management and allowing natural vegetation succession to occur. Land can be abandoned to passive rewilding deliberately or due to socio-economic change. Despite abandonment being a major driver of land use change, few have studied the long-term outcomes for vegetation and biodiversity in Western Europe. Studies are also biased towards sites that are close to seed sources and favourable to woodland colonisation. In this case-study, we reconstruct a time series of passive rewilding over 33 years on 25 ha of former farmland that had been subject to soil tipping, far from woodland seed sources. Natural colonisation by shrubs and trees was surveyed at three points during the time series, using field mapping and lidar. Breeding birds were surveyed at three time points, and compared with surveys from nearby farmland. Results showed that natural colonisation of woody vegetation was slow, with open grassland dominating the old fields for two decades, and small wetlands developing spontaneously. After 33 years, thorny shrub thickets covered 53% of the site and former hedgerows became subsumed or degraded, but trees remained scarce. However, the resulting habitat mosaic of shrubland, grassland and wetland supported a locally distinctive bird community. Farmland bird species declined as passive rewilding progressed, but this was countered by relatively more wetland birds and an increase in woodland birds, particularly songbirds, compared to nearby farmland. Alongside biodiversity benefits, shrubland establishment by passive rewilding could potentially provide ecosystem services via abundant blossom resources for pollinators, and recreation and berry-gathering opportunities for people. Although closed-canopy woodland remained a distant prospect even after 33 years, the habitat mosaic arising from passive rewilding could be considered a valuable outcome, which could contribute to nature recovery and provision of ecosystem services.

Invasive non-native species (INNS) are one of the major threats to global biodiversity. Climate change and garden bird-feeding may facilitate the establishment of INNS. The Red-billed Leiothrix Leiothrix lutea is a small woodland passerine, native to subtropical Asia, that is an INNS in several parts of the world, including Europe, following escapes from the aviculture trade. Recently, populations of Red-billed Leiothrix have established in Spain, Portugal, Italy and France. Previous studies have shown that much of Europe is suitable for the species, including southern Britain. The Red-billed Leiothrix has not previously been considered as at high risk of establishment in Britain, but we document recent records, including a cluster in southern England, suggesting that establishment may already be underway. We discuss the potential negative impacts of this invasive species on local ecosystems, and how a warming climate and garden bird-feeding might assist their establishment in temperate Europe. We also highlight the importance of improved recording to monitor the potential establishment of INNS, such as the Red-billed Leiothrix, in Britain.

Differences in population trends across a species' breeding range are ultimately linked to variation in demographic rates. In small songbirds, demographic rates related to fecundity typically have strong effects on population trends. Populations of a forest songbird, the wood warbler Phylloscopus sibilatrix, have been declining in many but not all regions of the European breeding range. We investigated if clutch size, hatching rate, nest survival and number of fledglings vary across Europe, and if nest survival is related to differences in the regionally dominant nest predator class (birds versus mammals). From 2009 to 2020, we monitored 1896 nests and used cameras at a subsample of 645 nests in six study regions: the United Kingdom (mid‐Wales, Dartmoor, the New Forest), Germany (Hessen), Switzerland (Jura mountains) and Poland (Białowieża National Park). Number of fledglings was lowest in the New Forest (1.43 ± CI 0.23), intermediate in Jura (2.41 ± 0.31) and Białowieża (2.26 ± 0.24) and highest in mid‐Wales (3.02 ± 0.48) and Dartmoor (2.92 ± 0.32). The reason for low reproductive success in the New Forest, Jura and Białowieża was low nest survival, and large clutch sizes in Białowieża did not compensate for high nest losses. High reproductive success in mid‐Wales and Dartmoor was due to high nest survival and large clutch sizes. Overall predation rates were similar everywhere despite variation between the regions in the dominant nest predator class. Unsuccessful nests in mid‐Wales were mainly predated by birds; in Dartmoor, the New Forest, Hessen and Jura similarly by birds and mammals; and in Białowieża exclusively by mammals. Regional reproductive success does not match the population trends recently reported for the wood warbler in the six study regions (i.e. high reproduction ≠ positive trend). Annual survival may be a decisive factor, but it is difficult to quantify for a nomadic species such as the wood warbler that rarely returns to the same breeding locations.

Natural succession of vegetation on abandoned farmland provides opportunities for passive rewilding to re-establish native woodlands, but in Western Europe the patterns and outcomes of vegetation colonisation are poorly known. We combine time series of field surveys and remote sensing (lidar and photogrammetry) to study woodland development on two farmland fields in England over 24 and 59 years respectively: the New Wilderness (2.1 ha) abandoned in 1996, and the Old Wilderness (3.9 ha) abandoned in 1961, both adjacent to ancient woodland. Woody vegetation colonisation of the New Wilderness was rapid, with 86% vegetation cover averaging 2.9 m tall after 23 years post-abandonment. The Old Wilderness had 100% woody cover averaging 13.1 m tall after 53 years, with an overstorey tree-canopy (≥ 8 m tall) covering 91%. By this stage, the structural characteristics of the Old Wilderness were approaching those of neighbouring ancient woodlands. The woody species composition of both Wildernesses differed from ancient woodland, being dominated by animal-dispersed pedunculate oak Quercus robur and berry-bearing shrubs. Tree colonisation was spatially clustered, with wind-dispersed common ash Fraxinus excelsior mostly occurring near seed sources in adjacent woodland and hedgerows, and clusters of oaks probably resulting from acorn hoarding by birds and rodents. After 24 years the density of live trees in the New Wilderness was 132/ha (57% oak), with 390/ha (52% oak) in the Old Wilderness after 59 years; deadwood accounted for 8% of tree stems in the former and 14% in the latter. Passive rewilding of these 'Wilderness' sites shows that closed-canopy woodland readily re-established on abandoned farmland close to existing woodland, it was resilient to the presence of herbivores and variable weather, and approached the height structure of older woods within approximately 50 years. This study provides valuable long-term reference data in temperate Europe, helping to inform predictions of the potential outcomes of widespread abandonment of agricultural land in this region.