Britain is home to several species of small mammals, which include rats, mice, voles, dormice and shrews. All of these are difficult to observe in the wild, and it is usually necessary to capture them to confirm their presence. By describing the vocal repertoire of small mammals in Britain, research published in British Wildlife by a team led by the BTO provides new possibilities for sound identification to be used as a non-invasive survey method. This has considerable potential to help conservation efforts by providing a cost-effective and robust method for detecting the presence of small mammals (e.g. Hazel Dormice in woodland, Brown Rats on seabird islands), which could be followed up with more intensive survey work if needed. It is likely that large volumes of data on small mammals are already being collected incidentally, but probably unknowingly, across Britain by bat workers using bat detectors. To maximise the value of bat surveys, the BTO Acoustic Pipeline improves the sound identification of bats, whilst also providing results for small mammals and other species groups. Download the appendix to the publication For the full article, see British Wildlife Volume 32, Number 3, December 2020 Download a zipped file containing original .wav audio clips (ZIP, 91MB) accompanying the publication

A newly published assessment of the evidence that climate change is causing biodiversity populations to decline as a result of divergent changes in the timing of consumer demands and the availability of species that they feed on, highlights significant evidence gaps. The earlier arrival of spring, measured by plants flowering, insects emerging, and the timing of egg laying and migrants arriving in birds, is one of the most obvious impacts of climate change on the natural world. These trends differ between different species’ groups, with plants tending to respond more quickly to warmer temperatures than insects, which have in turn have responded more quickly than birds. This has led many people to suggest that climate change is causing a mismatch (trophic asynchrony) between the timing of predators and prey, or herbivores and the plants that they eat, disrupting food networks and causing species to decline. In the most comprehensive review of the published literature on this topic to date, led by Edinburgh University but involving authors from seventeen other institutions including BTO, five criteria required to demonstrate that warming is having a negative impact on consumers through trophic asynchrony are identified: Consumers rely on a seasonal food resource The timing of peak consumer demand and peak food availability is diverging through time (asynchrony) Variation in asynchrony is linked to temperature Asynchrony negatively impacts the fitness of individual consumers Asynchrony negatively impacts consumer populations The majority of the 109 papers reviewed were from North America and Europe, showing a strong geographical bias in published studies; more data are required from aquatic systems and particularly the global south. Most studies described asynchrony in species reliant on a seasonal food resource, with almost two thirds providing evidence that, as expected, consumers were altering their phenology more slowly than their prey as a result of weaker temperature responses. Asynchrony is a widespread phenomenon. However, fewer than 8% of studies considered impacts on species’ populations and for only two species (both birds) were all five criteria documented; the Pied Flycatcher and Great Tit. This overview highlights the challenge researchers face in understanding how climate change affects complex ecological systems, and identifies some important priorities for future research, including a real need for long-term population monitoring data. Working with our thousands of volunteers, BTO initiatives like the Nest Record Scheme, Constant Effort Sites Scheme and Breeding Bird Survey enable us to do this. For example, we used these data to show that the sensitivity of breeding songbirds to changes in seasonal timing is linked to population change but cannot be directly attributed to declines in breeding productivity. More broadly, these schemes have been instrumental in tracking significant impacts of climate change on species distributions, populations and communities. To summarise, climate change is having widespread impacts on the natural world. This review shows that understanding the mechanisms behind these impacts is challenging and requires a combination of detailed ecological studies and long-term monitoring data to do so.

New research from BTO Scotland has investigated how to improve the effectiveness of the BTO/JNCC/RSPB Breeding Bird Survey (BBS) in monitoring Scotland’s birds. Since the launch of BBS in 1994, volunteers have covered thousands of random 1 km squares across the UK, and as a result we are now able to produce population trends for 117 of the UK’s commoner breeding bird species. Country-specific trends are also produced for a subset of species and these are of great use to a variety of stakeholders, including the devolved administrations. Scotland presents some unique challenges which make it difficult to achieve the levels of BBS coverage we would ideally like – most notably the rugged physical geography and a thinly spread human population in many areas. We need to better understand the constraints such challenges place on participation in order to further increase coverage in Scotland, and overcome any existing biases in survey effort. The research reviewed historic patterns of coverage for 958 BBS squares in Scotland. It revealed some significant differences in coverage, with lowland squares having been visited much more often than those over 600 m. On average, 44% of available visits to lowland squares had been completed versus 20% for high altitude squares. Coverage was highest in areas of high human population density whereas steeply sloping ground, conifer plantations, elevation, and ascent from the nearest road all had a negative effect on visit frequency. In order to address these issues, and increase coverage overall, a number of potential solutions were considered. Of these, the most favourable option was ‘Roving Observers’, allowing single one-off visits to a selection of carefully selected, seldom-covered remote squares. It was felt that this scheme might appeal to holidaying birdwatchers, Munro-baggers, and hillwalking birdwatchers, all of whom might enjoy exploring new parts of Scotland, collecting valuable data, and hopefully seeing some of Scotland’s more charismatic upland birds. In response to these findings, we launched the UK-wide BBS Upland Rovers scheme in 2017, where volunteers can sign up for single one-off visits (though two visits are encouraged where possible). This scheme proved to be very popular, with 125 Upland Rovers squares covered in 2019. The resulting data have already improved the representativeness of our trends for several widespread species, and have brought species such as Whinchat and Redshank closer to the 30-square average coverage threshold that would allow Scottish population trends to be produced. Although this style of coverage requires some compromises with respect to the ideal BBS survey method (two visits by the same observer for multiple years) it is clearly generating valuable data. By better-understanding the constraints we can continue to increase BBS coverage and we will gain an ever-clearer picture of the population trends underpinning Scotland’s iconic birdlife. Huge thanks to all of the survey volunteers for their invaluable input. Many of them go to extraordinary lengths to collect data from remote and challenging parts of Scotland, for which we are extremely grateful.

Research involving BTO documents a decline in numbers and a shift in range for Scaup in Europe.

Changes in woodland management have been linked to declines in birds and other wildlife but we know little about the impacts of such changes on our bat populations. All 17 of the bat species found breeding in the UK use woodlands and many are reliant on semi-natural broadleaved woodland. Because of the increasing pressures on our woodlands and their bat populations it is essential that we improve our understanding of how different types of woodland management affect their use by bats. The study was carried out on the Rushmore Estate on Cranborne Chase in southern England and forms part of a wider biodiversity project overseen by Andy Poore, Forest Manager, Rushmore Estate and Prof. Stuart Marsden of Manchester Metropolitan University (MMU). PhD student at MMU and Lead author Danny Alder used special acoustic recorders to capture the echolocation and other calls made by bats using the study sites. Through this he was able to identify the species involved and could then measure their activity across the different woodland habitats. Danny collected data on the structural features of the woodlands, many of which are the result of the management practices used. Features like the degree of canopy cover, tree size, density of the understorey and the amount of standing dead wood can influence a woodland’s suitability to bats. Eleven bat species were identified, including the rare Barbastelle, and there were clear differences between the different woodland management types in terms of both occupancy by bats and their activity. ‘Irregular High Forest’, a woodland type where the forest ecosystem is maintained intact by selective felling and characterised by its mixed-sized trees and complex structure, had the richest bat community and highest occupancy rates for most bat species, when compared to actively-coppiced stands and stands where interventions are very limited. Dr Danny Norrey of MMU produced the complex statistical models which helped shed light on the key differences in the habitats the bats were using. The study demonstrates how features associated with Irregular High Forest stands, including deadwood, understorey structure, open canopy areas and larger tree size, seemed to benefit multiple bat species across different foraging guilds. Barbastelle – a low-level forager – was significantly associated with areas of more open canopy across all of the different stand management types, though with highest occupancy in the Irregular High Forest stands. The importance of this, and the other features highlighted, should be taken into account when considering how best to manage woodland for bats.