Bush-crickets are a little-known group of insects that inhabit our marshes, grasslands, woods, parks and gardens. Some may be seen in the summer when they are attracted to artificial lights, but as most produce noises that are on the edge of human hearing, we know little about their status. There are suggestions that some bush-crickets may be benefiting from climate change, while others may be affected by habitat changes. But how to survey something that is difficult to see and almost impossible to hear? Advances in autonomous recording devices are transforming our understanding of bats, but the large-scale deployment of such devices has the potential to improve our understanding of other species groups that produce loud and characteristic sounds too. The original objective of BTO's Norfolk Bat Survey, led by Stuart Newson, was to trial the recording of bat activity using passive real-time detectors, to gauge the willingness of members of the public to engage in bat monitoring at a large scale, and to determine the suitability of automated identification routines for processing large volumes of citizen-science collected bat recordings. However, it soon became clear that bush-crickets were also being recorded in large numbers. Working with the Museum of Natural History in Paris and Natural England, BTO staff developed a computer algorithm to identify the sounds made by different species of bush-crickets. After carefully validating these state-of-the-art methods using field recordings in Norfolk, the daily activity patterns of different species of bush-cricket was examined to determine where different species live. The Speckled Bush-cricket, for example, would normally be easy to overlook because it occurs in vegetation and stridulates at a frequency too high for humans to hear. With over 260,000 recordings of this species collected through the Norfolk Bat Survey, this study found this species to be common and widespread, with a distribution that extends into the city of Norwich. At the other extreme, Great Green Bush-cricket, previously known from only a few locations in Norfolk, was recorded at two locations, of which one was a new site for this species. This research demonstrates the huge potential to take advantage of established large-scale bat monitoring to also collect high-quality monitoring data for bush-crickets. It is likely that large volumes of information on bush-crickets are already being collected incidentally by bat workers using static detectors, but this information is at best noticed and ignored. This work also marks an important step towards the development of automated sensor networks, which are likely to play growing role in the future biodiversity surveying, and the whole approach enables members of the public to become actively engaged in wildlife monitoring, with important conservation implications.

Experiences of nature provide many mental-health benefits, particularly for people living in urban areas. The natural characteristics of city residents’ neighborhoods are likely to be crucial determinants of the daily nature dose that they receive; however, which characteristics are important remains unclear. One possibility is that the greatest benefits are provided by characteristics that are most visible during the day and so most likely to be experienced by people. We demonstrate that of five neighborhood nature characteristics tested, vegetation cover and afternoon bird abundances were positively associated with a lower prevalence of depression, anxiety, and stress. Furthermore, dose–response modeling shows a threshold response at which the population prevalence of mental-health issues is significantly lower beyond minimum limits of neighborhood vegetation cover (depression more than 20% cover, anxiety more than 30% cover, stress more than 20% cover). Our findings demonstrate quantifiable associations of mental health with the characteristics of nearby nature that people actually experience.

Fifty years ago, volunteers began annual breeding bird surveys in woodlands as part of the Common Bird Census. Few probably would have anticipated the enormous changes the bird communities in those woodlands have shown, but their data have been a gold-mine for understanding how the many guises of environmental change are impacting birds. In our latest study we worked with colleagues at the University of Reading, Centre for Ecology and Hydrology, Butterfly Conservation and Natural England to assess how climate change and habitat interact to affect bird and butterfly populations. As climate warms, we expect species that are tolerant of warm climates to be least affected, or indeed to benefit in areas that were formerly too cold for them. Conversely, species that prefer cold climates are expected to fare poorly, perhaps by declining or retreating from warming areas. Following previous studies, we used the Species Temperature Index (STI), which corresponds to the average temperature across the European range of each species, to rank bird and butterfly species from cold-associated (e.g. Meadow Pipit, Willow Warbler, Chequered Skipper, Northern Brown Argus) to warm-associated (e.g. Cetti’s Warbler, Stonechat, Lulworth Skipper, Gatekeeper). Several studies have combined these STI values with the species’ population trends at individual sites to produce a composite “Community Temperature Index” (CTI). Most studies find this CTI is increasing, which is usually taken to mean that the community is increasingly dominated by species that prefer warm conditions. We took this further by looking separately at how the different species in the communities are faring. Although the bird community CTIs had increased, changes for constituent species weren’t as predicted. For example, the top 25% of birds as ranked by warmth-association had not increased as predicted but had declined on average. The overall increase in bird CTI was driven by a large decline in the abundance of the most cold-associated species and an increase for moderately warm-associated species. Importantly, the extent of the declines of the most cold- and warm-associated species was related to the amount of intensively managed land surrounding the monitored woodlands. This suggests that the lack of natural habitat in the surroundings makes it harder for cold-associated birds to find cool corners of sites, or to disperse away from warming regions. Butterfly results were subtly different but with similar conclusions about the role of intensively managed land. This provides a clear recommendation to land managers and conservation agencies – creating larger natural areas in strategic places will help species to cope with the changing climate.

Renewable energy is a key part of strategies to reduce the effects of climate change. However, there are concerns about the potential impacts of large renewable developments, such as offshore wind farms, on wildlife. A significant amount of research has been directed at understanding how these developments may affect marine wildlife, particularly seabirds. Key impacts on seabirds are likely to include increased mortality through collisions with wind turbines, and displacement from preferred foraging areas. However, whilst we can estimate what impact any development may have at an individual level, understanding what this means for the population as a whole is more complex. New research led by Aonghais Cook of the BTO has tested a variety of analytical tools, or models, to assess the likely population-level consequences of the impacts arising from any individual wind farm development. These include tools predicting the likelihood of a given outcome (e.g. the probability of a 25% decline) and those that compare scenarios with and without the development. The results demonstrate that conclusions about the significance of any population-level consequences differ according to the initial assumptions made about a seabird species’ survival, breeding success and population trend. The effect of these assumptions is particularly noticeable for approaches that predict the likelihood of a given outcome. In a world where our knowledge of wildlife populations is often imperfect, this may lead to situations where conclusions about the significance of any population-level impacts are driven by how knowledgeable we are about the population concerned, rather than by the magnitude of any impact. This research suggests that future assessments should compare the outputs of models considering scenarios for wildlife with and without any wind farm development. However, given that our knowledge of the population concerned can influence our conclusions, it is important that all assumptions used in the modelling are clearly stated. Judgement of whether any population-level consequences can be deemed acceptable should then be made with reference to our knowledge of the species concerned and its local, regional, national and international populations, ensuring that decisions about offshore wind farm development are made in the best possible way for wildlife.

The BirdTrends 2020 report is a one-stop shop for authoritative information about the population status of the common breeding birds of the wider UK countryside. The report is based on data gathered by the many thousands of volunteers who contribute to BTO-led surveys.