This article describes the terrestrial and freshwater animal trend data used in creating the 2023 State of Nature reports for the UK and its constituent countries. Trend data for long- (1970-2020/21) and short-term (2010-2020) periods have been calculated by fitting statistical models to measures of abundance (753 species) or occupancy (4979 species) across the UK. Trend data was also calculated for each constituent country: England, Northern Ireland, Scotland and Wales for reduced sets of species. Trends in abundance data were generally created from the analysis of repeat counts at specific sites. Trends in occupancy were created by analysing ad hoc species records of invertebrates provided by volunteers. Statistical methods partially controlled for the risk of bias and the noisy nature of such occupancy data. Trends were only calculated where the number of species records justified the creation of trend statistics. Species that make up three key groups of insects are identified in additional columns in the dataset, those responsible for key ecosystem functions: species providing freshwater nutrient cycling, pollinating insects and predators of crop pests. The data has one clear limitation in that it is only a partial representation of the fauna of the UK. Many cryptic, nocturnal or soil dwelling species are poorly recorded and even some easy to identify species such as amphibians and reptiles do not have a suitable recording scheme that captures abundance.

Capsule: The first UK European Turtle Dove Streptopelia turtur survey, in 2021, estimated the breeding population at 2092 territories.Aims: Changes in European Turtle Dove abundance in the UK have been monitored through schemes like the BTO/JNCC/RSPB Breeding Bird Survey, however, sample size is now too low to calculate robust trends going forward. The aims of this volunteer-based survey were to provide a new UK population estimate and create a baseline to monitor future population trends.Methods: A stratified random sample of one-kilometre squares were surveyed within the core counties for the species. Elsewhere, one-kilometre squares containing recent European Turtle Dove records were targeted. The survey used a two-visit territory mapping approach, with observers asked to get within 200 metres of potentially suitable nesting or foraging habitat. Visits were undertaken in the early morning, to coincide with peak vocal activity, from 11 May to 31 July.Results: The UK population estimate in 2021 was 2092 territories (95% confidence limits, 1559-2782). The species has become increasingly restricted to eastern and southeastern England, with 62.5% of the population estimated to occur in three counties: Kent (682 territories; 32.6%), Suffolk (326; 15.6%) and Essex (300; 14.3%). Additional hotspots occurred in other counties in eastern England, up to North Yorkshire.Conclusion: This result suggests a 98% decline in abundance since the 1968-1972 breeding atlas, similar to trends identified from UK bird monitoring schemes, and a substantial contraction in range since the 2007-2011 bird atlas. The temporary cessation of hunting along their European western flyway provides a vital window of opportunity to scale up the delivery of high-quality breeding habitat and increase food availability in the UK. The survey should be repeated in 2026, and regularly thereafter, to help monitor the effectiveness of conservation interventions.

Detecting biodiversity change and identifying its causes is challenging because biodiversity is multifaceted and temporal data often contain bias. Here, we model temporal change in species' abundance and biomass by using extensive data describing the population sizes and trends of native breeding birds in the United Kingdom (UK) and the European Union (EU). In addition, we explore how species' population trends vary with species' traits. We demonstrate significant change in the bird assemblages of the UK and EU, with substantial reductions in overall bird abundance and losses concentrated in a relatively small number of abundant and smaller sized species. By contrast, rarer and larger birds had generally fared better. Simultaneously, overall avian biomass had increased very slightly in the UK and was stable in the EU, indicating a change in community structure. Abundance trends across species were positively correlated with species' body mass and with trends in climate suitability, and varied with species' abundance, migration strategy and niche associations linked to diet. Our work highlights how changes in biodiversity cannot be captured easily by a single number; care is required when measuring and interpreting biodiversity change given that different metrics can provide very different insights.This article is part of the theme issue 'Detecting and attributing the causes of biodiversity change: needs, gaps and solutions'.

Wetland bird species have been declining in population size worldwide as climate warming and land-use change affect their suitable habitats. We used species distribution models (SDMs) to predict changes in range dynamics for 64 non-passerine wetland birds breeding in Europe, including range size, position of centroid, and margins. We fitted the SDMs with data collected for the first European Breeding Bird Atlas and climate and land-use data to predict distributional changes over a century (the 1970s–2070s). The predicted annual changes were then compared to observed annual changes in range size and range centroid over a time period of 30 years using data from the second European Breeding Bird Atlas. Our models successfully predicted ca. 75% of the 64 bird species to contract their breeding range in the future, while the remaining species (mostly southerly breeding species) were predicted to expand their breeding ranges northward. The northern margins of southerly species and southern margins of northerly species, both, predicted to shift northward. Predicted changes in range size and shifts in range centroids were broadly positively associated with the observed changes, although some species deviated markedly from the predictions. The predicted average shift in core distributions was ca. 5 km yr−1 towards the north (5% northeast, 45% north, and 40% northwest), compared to a slower observed average shift of ca. 3.9 km yr−1. Predicted changes in range centroids were generally larger than observed changes, which suggests that bird distribution changes may lag behind environmental changes leading to ‘climate debt’. We suggest that predictions of SDMs should be viewed as qualitative rather than quantitative outcomes, indicating that care should be taken concerning single species. Still, our results highlight the urgent need for management actions such as wetland creation and restoration to improve wetland birds’ resilience to the expected environmental changes in the future.

Even during ongoing global biodiversity losses and extinctions, numerous species have shown recoveries in terms of increased abundance and/or range extent. Understanding the mechanisms that contribute to, or limit, these recoveries is critical not just to ensure they continue, but to promote similar recoveries across broader ecosystems. Here, we explore the changes in abundance and range extent of selected 47 recovering species (24 mammals and 23 birds) in Europe using official data reported by EU Member States and supplemented using the Living Planet Index database. We investigate how the diversity of ongoing threats and conservation measures contribute to the likelihood and extent of recoveries. For birds, long-term recoveries were less likely among species impacted by a greater diversity of threats, although this may be mitigated by the diversity of conservation measures in place. Similarly, for mammals, populations with reported threats recovered less quickly while those with management actions in place recovered more quickly. To achieve the aims of the UN Decade on Restoration, we need to ensure, even for recovering species , that threats continue to be reduced and that conservation management actions are ongoing and effective.

This repository contains the input data, species level results and code associated with the paper: Drivers of the changing abundance of European birds at two spatial scales.

Abstract Although global assessments provide evidence of biodiversity decline, some have questioned the strength of the evidence, with local assemblage studies often showing a more balanced picture of biodiversity change. The multifaceted nature of biodiversity and imperfect monitoring datasets may partially explain these findings. Here, using an extensive dataset, we find significant biodiversity loss in the native avifauna of the European Union (EU). We estimate a decline of 17–19% in the overall breeding bird abundance since 1980: a loss of 560–620 million individual birds. Both total and proportional declines in bird numbers are high among species associated with agricultural land. The distribution of species’ population growth rates (ln) is centered close to zero, with numerical decline driven by substantial losses in abundant species. Our work supports previous assessments indicating substantial recent biodiversity loss and calls to reduce the threat of extinctions and restore species’ abundances, for the sake of nature and people.

This archive contain the two input datasets of bird population estimates and trend estimates underpinning the journal article: Abundance decline in the avifauna of the European Union reveals global similarities in biodiversity change. It also contains the species level results obtained from the Bayesian hierarchical model described in section 2.2.1 of the paper.

While global assessments provide evidence of biodiversity decline, some have questioned the strength of the evidence, with local assemblage studies often showing a more balanced picture of biodiversity change. The multifaceted nature of biodiversity and imperfect monitoring datasets may partially explain these findings. Here, using an extensive high-quality dataset, we find significant biodiversity loss in the native avifauna of the European Union (EU). We estimate a decline of 17-19% in overall breeding bird abundance since 1980: a loss of 560-620 million individual birds. Both total and proportional declines in bird numbers are high amongst species associated with agricultural land. The distribution of species’ population growth rates (ln) is centred close to zero with numerical decline driven by substantial losses in abundant species. Our work supports previous assessments indicating recent biodiversity loss and calls to reduce the threat of extinctions and restore species’ abundances, for the sake of nature and people.

Conservation resources are limited and need to be used where they can be most effective. Deciding where within a species range to implement conservation interventions requires knowledge of where threats operate and consideration of multiple spatial issues concerning patterns in abundance across species' ranges, and geographical and environmental gradients in these and other traits across species' ranges. Although these biogeographical patterns have been of great interest to ecologists for many years, the implications of these patterns for conservation are often unclear. Here we review these patterns in the context of targeting spatial conservation. We find that an inconsistent use of terminology, a lack of consistent rules and the use of imperfect datasets, hampers us drawing firm conclusions on the nature of these patterns. Evidence that abundance and ecological traits change systematically towards range edges is inconclusive. Abundance variation is influenced by many factors independent of position within a species range, including habitat type, habitat quality, environment, interspecific competition, dispersal ecology and metapopulation dynamics. This results in complex textured abundance patterns compared to a simple theoretical core-edge gradient. We conclude that any conservation practitioner looking to target the location of interventions will need to examine these patterns and processes for the species of interest. Current knowledge does not adequately inform spatial conservation prioritization for single-species conservation programmes and incorporating the complexities of spatial processes is challenging. The development of tools to inform spatial targeting of resources for single- or multiple-species conservation is required urgently to enable better use of conservation resources.

Developing biodiversity indicators for African birds 1 2 S. R. Wotton1, M. A. Eaton1, D. Sheehan2, F. Barasa Munyekenye3, I. J. Burfield4, S. H. M. 3 Butchart4,5, K. Moleofi6, D. Nalwanga-Wabwire7, P. K. Ndang’ang’a8, D. Pomeroy9, K. J. 4 Senyatso6 and R. D. Gregory1,10. 5 6 7 1RSPB Centre for Conservation Science, The Lodge, Sandy, Bedfordshire SG19 2DL, UK. 2White 8 Cottage, Strefford, Shropshire, SY7 8DE. 3Nature Kenya, P.O. Box 44486, Museum Hill Road, 9 Nairobi, Kenya. 4BirdLife International, The David Attenborough Building, Pembroke Street, 10 Cambridge, CB2 3QZ, UK. 5Department of Zoology, University of Cambridge, Downing Street, 11 Cambridge CB2 3EJ, UK. 6BirdLife Botswana, P. O. Box 26691, Kgale View, Gaborone, 12 Botswana. 7Nature Uganda, P. O. Box 27034, Katalima Crescent, Kampala, Uganda. 8BirdLife 13

Organisations acting to conserve and protect species across large spatial scales prioritise to optimise use of resources. Spatial conservation prioritization tools typically focus on identifying areas containing species groups of interest, with few tools used to identify the best areas for single-species conservation, in particular, to conserve currently widespread but declining species. A single-species prioritization framework, based on temporal and spatial patterns of occupancy and abundance, was developed to spatially prioritize conservation action for widespread species by identifying smaller areas to work within to achieve predefined conservation objectives. We demonstrate our approach for 29 widespread bird species in the UK, using breeding bird atlas data from two periods to define distribution, relative abundance and change in relative abundance. We selected occupied 10-km squares with abundance trends that matched species conservation objectives relating to maintaining or increasing population size or range, and then identified spatial clusters of squares for each objective using a Getis-Ord-Gi* or near neighbour analysis. For each species, the framework identified clusters of 20-km squares that enabled us to identify small areas in which species recovery action could be prioritized. Our approach identified a proportion of species’ ranges to prioritize for species recovery. This approach is a relatively quick process that can be used to inform single-species conservation for any taxa if sufficiently fine-scale occupancy and abundance information is available for two or more time periods. This is a relatively simple first step for planning single-species focussed conservation to help optimise resource use.

Capsule The first European Bird Census Council (EBCC) Atlas of European Breeding Birds has been widely used in scientific publications. Aims To quantify how scientific publications have used data from the first European Bird Census Council (EBCC) Atlas of European Breeding Birds, what the topics of these studies have been, and to identify key aspects in which a second European Breeding Bird Atlas will provide new opportunities for basic and applied science. Methods We searched Google Scholar to find papers published in scientific journals that cited the first atlas. We analysed the contents of a random selection of 100 papers citing this atlas and described the way these papers used information from it. Results The first atlas has been cited in 3150 scientific publications, and can be regarded as a fundamental reference for studies about birds in Europe. It was extensively used as a key reference for the studied bird species. A substantial number of papers re-analysed atlas data to derive new information on species distribution, ecological traits and population sizes. Distribution and ecology were the most frequent topics of studies referring to the atlas, but this source of information was used in a diverse range of studies. In this context, climate change, impact of agriculture and habitat loss were, by order, the most frequently studied environmental pressures. Constraints in the atlas, such as the poor coverage in the east of Europe, the lack of information on distribution change and the coarse resolution were identified as issues limiting the use of the atlas for some purposes. Conclusions This study demonstrates the scientific value of European-wide breeding bird atlases. A second atlas, with its almost complete coverage across Europe, the incorporation of changes in distribution between the two atlases and the inclusion of modelled maps at a resolution of 10 x 10 km will certainly become a key data source and reference for researchers in the near future.

Capsule: The second national survey of Twite Linaria flavirostris estimated a UK breeding population of 7831 pairs (95% confidence limits: 5829-10137) in 2013.Aims: To estimate the breeding population size of Twite in the UK and constituent countries and to calculate change since the 1999 survey.Methods: Counts of Twite were made on three visits between May and July across a stratified random sample of 1-km squares in England, Scotland and Wales. In Northern Ireland, a complete census was made of the known range and adjacent 1-km squares with suitable habitat. Field surveys involved walking line transects 200 m apart and, in suitable nesting habitat, making 5-minute stops at 100 m intervals to scan and listen for Twite.Results: The UK population of Twite was estimated at 7831 pairs (95% CL: 5829-10137). This was 21% lower but not significantly different from the 1999 survey estimate. Scotland held 98% of the UK population (7640, 95% CL: 5629-9954). There were an estimated 164 pairs (95% CL: 76-297) in England, a significant decline of 72% from 1999. Estimated totals for Wales and Northern Ireland were 16 (95% CL: 10-24) and 18 pairs respectively.Conclusion: The second national survey suggests a moderate decline in the UK Twite population since 1999 but with considerable variation between countries. Further work is required to understand the drivers of population change across breeding populations.

Capsule: The population size of Western Capercaillie Tetrao urogallus in Scotland was estimated at 1114 individuals with 95% confidence intervals (CIs) of 805-1505. Aim: To produce an updated estimate of Capercaillie population size in Scotland, with improved precision from, but retaining comparability with, previous surveys. Methods: A random sample of 2 km long line transects was surveyed throughout the current range of the Capercaillie, during winter 2015-16, with sampling in three separate strata. Multi-covariate distance sampling was used to fit detection functions to the Capercaillie data, deriving national, regional and sex-specific estimates of density and abundance. Results: Across 741 transects, 136 Capercaillie were recorded in 120 separate encounters, giving rise to a population estimate of 1114 individuals (95% CIs: 805-1505). This estimate is 13% lower than that from the previous survey in 2009-10 but the difference is not statistically significant. Most of the population (83%) was estimated to occur in Strathspey, with much smaller numbers in the rest of the range. Conclusion: The Capercaillie population in Scotland remains at a critically low level. Further evidence of decline in edge of range subpopulations raises serious concern over the viability of Capercaillie in these areas, whereas numbers appear stable in the core of the range in Strathspey. The use of a revised survey design, with greater sampling in the core of the range, improved estimate precision.

•A clear overview of biodiversity status is needed to allow informed decision making.•We used a range of types of species status data to create three biodiversity metrics.•The metrics were populated with data for a broad range of taxonomic groups in the UK.•We explore reducing residual taxonomic bias and improving these and similar metrics.

Capsule: The fifth UK and the Isle of Man survey of Hen Harrier in 2016 showed varying trends by country and region.Aim: To estimate the size of the breeding Hen Harrier population (with associated 95% confidence intervals) in the UK and Isle of Man, constituent countries and Scottish regions, in 2016 and calculate population change over the five surveys to date.Methods: Complete surveys were made of all 10-km squares likely to be occupied by breeding Hen Harriers in England, Wales, Northern Ireland and the Isle of Man, using standard methods developed for previous national surveys. In Scotland, self-selected 10-km squares were surveyed by volunteers and a stratified random selection of the remaining 10-km squares within the known breeding range was surveyed.Results: The UK and Isle of Man Hen Harrier population was estimated at 575 territorial pairs (95% confidence limits, 477-694), a non-significant decline of 13% since 2010 but a significant decline of 24% since 2004. Scotland held the majority (80%) of the population with 460 (359-573) territorial pairs. Elsewhere, 46 territorial pairs were recorded in Northern Ireland, 35 in Wales, 30 in the Isle of Man and four in England. Significant decreases were recorded in the number of pairs in Scotland using grouse moor (-57%) and young forest (-54%).Conclusion: The combined breeding population of Hen Harriers in the UK and Isle of Man has shown a non-significant decline between 2010 and 2016. There were notable decreases in England, Northern Ireland and Wales since 2010.

Capsule: In 2014 a survey of Red-billed Choughs Pyrrhocorax pyrrhocorax in the UK and Isle of Man found substantial variation in regional trends. The population has, however, remained stable overall since 2002, with a total of 433 breeding pairs recorded.Aims: The aim of the survey was to produce new estimates of the breeding populations and additional non-breeding birds for the Red-billed Chough in the UK and Isle of Man, and calculate national and regional population trends since previous surveys in 2002 and 1992.Methods: A complete census was attempted, using similar field methods to previous surveys. All known breeding sites and areas of adjacent suitable habitat within the range were surveyed between April and June 2014, with additional surveys on the Isle of Man in 2015. Evidence of breeding was established based on behaviours recorded during two standard visits.Results: The UK and Isle of Man population was estimated at 433 pairs, the majority found in Wales (55%) and Isle of Man (31%). Increases in the Isle of Man, Cornwall and south Wales contrasted with declines recorded in Scotland and in parts of north and mid-Wales. Trends differed regionally and between coastal and inland nesting areas.Conclusions: Numbers of Choughs in the UK and Isle of Man remained stable overall between 2002 and 2014, but trends varied between geographically distinct populations, suggesting the action of diverse drivers of change. Conservation efforts need to be responsive to these pressures by maintaining and enhancing habitat and food resources where required. Where populations are small, research needs to be targeted towards identifying critical demographic stages and facilitating gene flow among adjacent populations.

Biological invasions are not only events with substantial environmental and socioeconomic impacts but are also interesting natural experiments, allowing the study of phenomena such as the cultural evolution of bird song following introduction. We took an excellent opportunity to compare the distribution of dialects of the yellowhammer Emberiza citrinella, a small Eurasian passerine, in its native source region (Great Britain) and invaded range (New Zealand) more than hundred years after relocation. Recent field recordings (including those provided by volunteers within a citizen science project) were complemented by those from archives, each assigned to appropriate dialect by visual inspection of a sonogram, and the resulting spatial patterns of dialect distribution were interpreted using historical data on the yellowhammer invasion. The two countries differ markedly in the composition and distribution of dialects. New Zealand populations sing a greater number of different dialects, seven in total, five of which were not detected in the current British population, but have been reported by previous studies from the continental Europe. Two identified localities of capture (Brighton, Sussex, UK) and release (Dunedin, Otago, NZ) differ even more strikingly, having no dialects in common. The largely sedentary nature of yellowhammers allows for two mutually exclusive explanations for European dialects being detected in New Zealand but not in Great Britain: 1) the corresponding song types have emerged de novo in New Zealand, through convergent cultural evolution; 2) the dialects have disappeared from Great Britain, while being preserved in New Zealand. Indirect evidence from the widespread occurrence of these dialects in continental Europe and the reported stability of yellowhammer song, supports the latter explanation. We suggest that the yellowhammer dialect system is an avian equivalent of a phenomenon already noted in human languages, in which ancient words or structures are retained in expatriate communities.