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COVID-19 restrictions significantly biased BTO/JNCC/RSPB Breeding Bird Survey coverage across the UK allowing indicative trends to be produced for approximately one-third of species in England only. To investigate the effect that COVID-19 restrictions had on participation in and coverage of the Breeding Bird Survey (BBS), and to quantify the likely impacts on population change reporting based on 2020 data. We determined geographic, seasonal, and habitat coverage for the BBS in 2020 and compared this to previous years, and quantified the scale of biases and reductions in sample size for target species. We degraded existing BBS data (1994–2019) to simulate 2020 coverage and produced population change estimates using three methods applied to the complete and degraded data to assess the impacts of 2020 coverage on emergent trends. In 2020, 49% fewer survey squares were visited compared to 2019. Reductions were greatest in Wales, Scotland, and Northern Ireland, and in the early breeding season, when 90% fewer visits were made. The few early visits completed were on atypical dates and showed marked habitat biases. Individual species were detected in 23–96% fewer squares than normal. Population change estimates derived using routine trend models were negatively biased in up to 96% of species, with errors greatest for species normally detected on early visits. Alternative trend models using visit-specific parameterization or focussing only on late season visits overcame coverage biases for some species. Lockdown restrictions associated with the COVID-19 outbreak meant it was not possible to produce population trend information for UK, Wales, Scotland, or Northern Ireland in 2020. Indicative long-term trends could be produced in England only for a subset of about 40 species. We recommend managers of citizen science schemes undertake similar analyses to assess the scale of coverage biases when unforeseen events cause temporary, but substantial changes, in sampling effort. [ABSTRACT FROM AUTHOR]

Capsule: Current UK distributions of non-native birds poorly match areas identified as being climatically suitable. Aims: Non-native species are spreading at unprecedented rates and though invasions are expected to increase under climate change, evidence for this is mixed. We assess climatic suitability throughout the UK based on the apparent match to the climate in species’ native ranges and investigate potential climatic limitation within the non-native range. Methods: Climate was characterized within polygons representing the native ranges of 167 potentially invasive species. Parts of the UK with current and future climate similar to that in the native range were deemed climatically suitable. The incidence of recent observations inside and outside suitable areas was used to test hypotheses about climatic limitation of non-native ranges. Results: Climate matching suggests that 69 of 167 non-native bird species could currently find climatically suitable areas for establishment in the UK. Future climate change would see this number increase by 14% by 2080. However, observed occurrences of non-native species in the UK were not significantly correlated to climatic suitability. Only 44 of the 69 species with suitable climate in the UK were present. Moreover, 85% of species observed in the UK had some UK occurrences in climatically unsuitable areas and for 57 species their entire UK range was in climatically unsuitable areas. Similar results were apparent for the subset of 12 species with established UK populations. Conclusions: Climate matching provides a relatively poor indication of the extent of current and future suitable areas because species can adapt to new climates or other factors constrain the native range and many climatically suitable areas are currently unoccupied. Improvements to climate matching techniques and ongoing surveillance are required to refine predictions to support effective management policies. [ABSTRACT FROM AUTHOR]

Capsule:Across Britain, breeding Eurasian CurlewNumenius arquataare less numerous and have shown greater population declines in areas with more arable farming, woodland cover and higher generalist predator abundance. Aims:We present the first national-scale analysis of the potential drivers of Curlew population change in Britain, which is needed to guide conservation action for this globally near-threatened, declining species. Methods:Breeding Bird Survey data and environmental predictors were used to model variation in Curlew abundance in 1995–99 and 2007–11, and population change between these periods. Results:Arable farming and woodland cover were negatively associated with Curlew abundance and population declines. Curlew abundance was positively associated with extent of protected area coverage and gamebird numbers. Abundance and population change were positively associated with cooler temperatures and higher summer rainfall, but negatively associated with numbers of generalist predators. Conclusions:We found support for the negative effects of intensive agriculture, forestry, increases in generalist predator populations and climate warming on Curlew abundance and population change. Effective site protection and measures to reduce generalist predator abundance may be important conservation measures, together with improving breeding habitat quality in the wider countryside. [ABSTRACT FROM PUBLISHER]

Species distribution models (SDMs) are one of the most important GIScience research areas in biogeography and are the primary means by which the potential effects of climate change on species’ distributions and ranges are investigated. Dispersal is an important ecological process for species responding to changing climates, however, SDMs and their subsequent spatial products rarely reflect accessibility to any future suitable environment. Dispersal-related movement can be confounded by factors that vary across landscapes and climates, as well as within and among species, and it has therefore remained difficult to parametrise in SDMs. Here we compared 20 models that have previously been used (or have the potential to be used) to represent dispersal processes in SDM to predict future range shifts in response to climate change. We assessed the different dispersal models in terms of their accuracy at predicting future distributions, as well as the uncertainty associated with their predictions. Atlas data for 50 bird species from 1988 to 1991 in Great Britain were treated as base distributions (t1), with the species–environment relationships extrapolated (using three commonly used statistical methods) to 2008–2011 (t2). Dispersal (in the form of the 20 different models) was simulated from the base distribution (t1) to 2008–2011 (t2). The results were then combined and used to identify locations that were both abiotically suitable (obtained from the statistical methods) and accessible (obtained from the dispersal models). The accuracy of these coupled projections was assessed with the 2008–2011 atlas data (the observed t2distribution). There was substantial variation in the accuracy of the different dispersal models, and in general, the more restrictive dispersal models (e.g. fixed rate dispersal) resulted in lower accuracy for the metrics which reward correct prediction of presences. Ensemble models of the dispersal methods (generated by combining multiple projection outcomes) were created for each species, and a new Ensemble Agreement Index (EAI), which ranges from 0 (no agreement among models) to 1 (full agreement among models) was developed to quantify uncertainty among the projections. EAI values ranged from 0.634 (some areas of disagreement and therefore medium uncertainty among dispersal models) to 0.999 (large areas of agreement and low uncertainty among dispersal models). The results of this research highlight the importance of incorporating dispersal and also illustrate that the method with which dispersal is simulated greatly impacts the projected future distribution. This has important implications for studies aimed at predicting the effects of changing environmental conditions on species’ distributions. [ABSTRACT FROM AUTHOR]

CapsuleThe breeding Woodcock population in Britain in 2013 was estimated at 55 241 males (95% CL: 41 806–69 004), suggesting a large-scale decline that is supported by 2 additional sources of data. AimsTo provide an updated estimate of the size of Britain's breeding Woodcock population, measure recent trends and identify spatial patterns of change. MethodsDisplaying male Woodcock were surveyed at a stratified sample of 834 randomly selected sites. Population estimates were compared with a baseline survey conducted in 2003 and the trend with data from annual Woodcock counts (2003–13) andBird Atlas 2007–11. ResultsWoodcock were estimated to be present at 22% of 1 × 1 km squares containing ≥10 ha of woodland, compared to 35% in 2003. The British population estimate fell by 29% between 2003 and 2013. The Atlas suggests that presence at the 10 × 10 km scale has declined by 56% between 1970 and 2010. Both data sources suggest regional variation in the rate of decline, with losses greatest in the West and South. ConclusionThe Woodcock's population size and breeding range appear to be declining severely across Britain. Regional variation in the rate of decline might be explained by the distribution of large continuous woodlands. [ABSTRACT FROM AUTHOR]

CapsuleTrends in young woodland availability influenced population trends and abundance of Tree Pipit and Lesser Redpoll, but not 10-km square occupancy. AimsTo investigate whether changes in availability of young woodland could have driven population change, and trends in abundance and occupancy, of declining Tree Pipit and Lesser Redpoll populations in Britain. MethodsModelling approaches used annual population indices and woodland planting statistics. Abundance and occupancy change between two bird atlases were examined in relation to changes in woodland availability from two woodland inventories. ResultsEnglish declines were strongly associated with decreases in young coniferous woodland availability and less strongly with increases in young broadleaved woodland. Abundance was related to the area of young woodland in corresponding 10-km squares. Young woodland availability declined between forest inventories and species occupancy maintained in 10-km squares with more young woodland; however squares that showed retention or increases in occupancy showed higher reductions in woodland. ConclusionWe suggest declining availability of young coniferous woodland contributed to Tree Pipit and Lesser Redpoll population trends in England. Although likely to be the case in Scotland and Wales, the lack of sufficient temporal data inhibited our ability to test this properly. This work suggests that woodland availability was not the primary driver of Tree Pipit or Lesser Redpoll population trends. [ABSTRACT FROM AUTHOR]

CapsuleThe recent population decline of Whinchats has accelerated, including core breeding areas of Britain. Contrasting patterns of change with Stonechat suggest a large-scale environmental driver is affecting the entire Whinchat population. AimsTo explore broad geographical and landscape related differences in long-term patterns of population change in the Whinchat and Stonechat across Britain to identify candidate mechanisms of change. MethodsThe study uses 40 years of large-scale, long-term data from a series of three atlas studies to compare trends in range and abundance in Whinchats and Stonechats relative to landscape and weather variables. ResultsFor Whinchats there has been a long-term and accelerating decline in abundance, that includes stronghold areas of Britain. The Stonechat population has undergone a net gain in abundance with regional and altitudinal variations. These two very different patterns of change suggest the relative ubiquity of decline in Whinchats has a common source affecting the whole population. ConclusionsThe scale and magnitude of decline in Whinchats should stimulate a revision of the species conservation status in Britain, with renewed focus on studying the species' ecology across its breeding and winter range in order to determine the likely large-scale drivers of its decline. [ABSTRACT FROM PUBLISHER]

Aims: To assess which components of habitat are associated with Hawfinch occupancy at landscape (10-km), local (tetrad) and fine (nest) spatial scales, during a period of population decline and range contraction. Methods: Bird Atlas 2008-11 data were used to determine areas of Hawfinch loss and persistence over 20 years. Current habitat was measured and compared to look for correlates that helped explain the differing status at both 10-km and tetrad scales. Fine scale habitat data collected at nest sites were compared with random locations to investigate within-wood nest site selection. Results: At both 10-km and tetrad scales, Hawfinch persistence is more likely where woodland cover is greater. Recent woodland management was less evident in tetrads where the species persisted. At the nest site scale, the only relationship detected was for nests to be close to canopy openings. Conclusions: Maintaining and increasing broadleaved woodland area is likely to benefit Hawfinch. Within woods, maintenance and creation of open areas may enhance nesting opportunities. [ABSTRACT FROM AUTHOR]

Capsule Farmland bird species occurred at low densities and were highly aggregated in a small proportion of available pastures, stubble fields and farmyards. Aim To document the current distribution and abundance of farmland birds and their habitats within the lowland farmland of Britain in winter. Methods Over three winters volunteer observers visited a stratified random sample of 1090 i-km squares within which they counted a suite of 30 farmland bird species and mapped agricultural habitats. Results For individual species, less than 10% of habitat patches were occupied and densities in occupied patches were low. Several differences were apparent in patterns of relative abundance compared to the 1980s. In particular marked declines of Tree Sparrow and Corn Bunting were apparent. The national distribution of cereal stubbles was localized. A large proportion of most species was found in grassland. Positive associations at the patch scale were apparent for improved grassland by invertebrate feeders and cereal and maize stubbles and farmyards, mostly by granivores. Conclusion Many farmland passerines are highly aggregated, even within particularly favoured field types. These results are consistent with winter food resources being highly localized and the need to create more food-rich patches if declines are to be reversed. [ABSTRACT FROM AUTHOR]

Capsule Perimeter counts underestimate the number of birds using agricultural fields. Aims To determine the degree to which farmland birds may be undercounted on field surveys and the factors influencing this. Methods In a study of 96 fields, birds in the field were counted during a walk of the perimeter. Afterwards transects were walked across the field to determine the number of birds missed. Additionally in a national survey we looked at the birds seen in field transects expressed as a proportion of the total seen in the transect and on perimeter counts. Results To obtain an accurate count of birds on a field requires the use of the whole-area search methodology especially for species such as Grey Partridge Perdix perdix, Snipe Gallinago gallinago, Skylark Alauda arvensis and Meadow Pipit Anthus pratensis. However, for a large number of species, including thrushes, flocking finches and buntings, over 90% of individuals can be recorded using the much less time-consuming perimeter count method. Conclusions Perimeter counts are likely to be reliable for most species but special efforts may be required For a few cryptic species. [ABSTRACT FROM AUTHOR]

Capsule The winter distribution of Golden Plover and Lapwing has shifted east since the mid-1980s, perhaps in response to climate change. Aims To combine analyses of winter trends on wetlands and flocks on farmland to assess the current status of Golden Plover and Lapwing in one of their main wintering regions. Methods Winter trends were derived from monthly counts on estuaries and wetlands for the period 1 974-2002 (the Wetland Bird Survey). Winter distribution on farmland was assessed using casual records of large flocks and surveys of a stratified random sample of 1-km squares (the Winter Farmland Bird Survey). Results Regional trends showed a pronounced increase in numbers of both species since i 974 on the east coast, with a smaller increase on the south coast. Numbers in the west and north tended to decline. Flocks on farmland were concentrated in eastern Britain unlike the situation in the 1980s. Conclusions The winter distribution of Golden Plover and Lapwing has shifted to the east, resulting in large numbers on the east coast and in the arable east of Britain. The implications of this shift, especially in relation to known habitat associations, are discussed. [ABSTRACT FROM AUTHOR]

The results of a national survey of wintering Skylarks Alauda arvensis undertaken by the British Trust for Ornithology (BTO) between November 1997 and February 1998 are reported here. Over three visits, volunteers counted Skylarks and mapped habitats in 541 1-kin squares selected from the Skylark's winter range based on BTO Winter Atlas data and a stratified random sampling approach. Four landscape strata were defined from the Institute of Terrestrial Ecology landscape classification: arable, pastoral, marginal upland and saltmarsh. The survey counts underestimated Skylark abundance, but were good measures of relative abundance across habitat types. The two best predictors of Skylark presence-absence at the landscape scale were the availability of coastal and farmland habitats. Squares with saltmarsh had the highest densities and occupancy (80% of squares). At the patch scale crop stubbles, especially weedy cereal stubbles, were used significantly more than expected by chance. Oilseed rape was positively selected whereas cereal crops were used in proportion to availability and grazed grass was avoided. Skylarks avoided fields smaller than 2.5 ha and selected fields larger than 7.5 ha. We estimate that in midwinter there may be less than 1-2 ha of weedy cereal stubble per 1-km square. We recommend the retention of over-winter stubbles for the conservation of Skylarks and other farmland birds, and research on stubble management and effects on grain availability and arable weed regeneration on Skylark use. [ABSTRACT FROM AUTHOR]

We report on the 1997 national Woodlark survey which was organized by the Royal Society for the Protection of Birds, the British Trust`for Ornithology and English Nature. In 1997, between 1426 and 1552 Woodlark territories were located in Britain. There has been a considerable increase in the population since the only previous national survey, in 1986, when approximately 250 territories were found. The five regions of population that were apparent in 1986 all showed major increases, in particular in Breckland and the Suffolk Sandlings. Over 85% of territories occurred on heathland or within forest plantations. The ratio varied between regions: plantations were more commonly used in the north and east whereas more Woodlarks utilized heathland in the south. Woodlarks in Devon bred almost exclusively on farmland. More than three-quarters of the forest population was `found in young plantations, particularly in stands of two and three year old trees. Most Woodlark territories were located on sandy soils, with nearly 70% specifically on acid sandy soils. Reasons for the observed increase and range expansion are discussed, as are the implications of habitat management practices. [ABSTRACT FROM AUTHOR]