New BTO research has examined the extent to which data on avian electrocutions and collisions are collected by companies responsible for high-voltage powerlines across Europe, and made recommendations to develop best practice. The continued increase in global energy demand requires expanding networks of power supply. High-voltage overhead powerlines, however, pose a collision and electrocution risk to some bird species if poorly sited or designed. Most powerline companies are legally required to mitigate these impacts, and so a range of data on bird mortality, abundance and mitigation effectiveness are often collected. But such data are not always available or accessible, preventing a wider-scale understanding of how vulnerable species may be. A new BTO paper published this week, in collaboration with RSPB, and the Renewables Grid Initiative, summarises the results of a questionnaire and workshop that brought together industry, conservationists and academics within Europe, to discuss these aspects and potential ways forward. Despite enthusiasm for sharing information, to date the task has been hampered by the lack of a centralised database, standardisation of data collection methods and data confidentiality. To overcome these barriers, a stepwise approach is suggested, developing further guidance around field methods, and collating broader information about individual studies. This approach would, in time, help unlock the full potential value of these data, reducing potential impacts on vulnerable bird populations.

Bird song helps us to build and maintain connections with the natural world and is a core component of natural soundscapes. Song, and in particular the diversity of that song at a given location, plays an important role in defining the quality of our engagement with soundscapes. Natural soundscapes vary with season, differ between locations, and will have changed over time, not least because of the long-term declines documented in bird populations across the globe. Widespread reductions in bird abundance and species richness are likely to have reduced the quality of our connections with natural soundscapes, and this is something that is explored in this paper, led by Cat Morrison at the University of East Anglia. The lack of historical recordings makes it difficult to assess how the quality of natural soundscapes might have changed over time. While we can compare recently recorded soundscapes with future ones, those from today are already degraded and we lack baseline data on how they would have once sounded. This new work uses a novel approach, reconstructing ‘lost’ soundscapes from the information collected by volunteers for bird surveys operated across Europe and North America, including data submitted through the BTO/JNCC/RSPB Breeding Bird Survey. By combining these survey data with recordings for over 1,000 species, taken from the online Xeno Canto database of bird songs and calls, the authors reconstruct soundscapes at more than 200,000 locations over the past 25 years. The protocol used for constructing these soundscapes applied the same rules for translating survey data into soundscape contribution across all species; while imperfect, because it does not capture variation in how often and for how long different species vocalise, the approach does reflect much of the inherent variation between species and provides valuable insight to how these communities would have sounded at different points in time. The acoustic properties of the reconstructed soundscapes could then be explored statistically through a series of standard measures, capturing the richness, evenness, amplitude and heterogeneity of each soundscape. While these measures broadly mirror avian species richness and abundance, they are primarily driven by song complexity and diversity across the contributing species. Because of this, the measures describe the key components of these soundscapes, predicted to underpin public perceptions of the quality of their experience of the natural world. The analysis reveals variation in soundscape quality, both across sites and over time. The results reveal a chronic deterioration in soundscape quality, defined as a reduction in acoustic diversity and/or intensity, across both North America and Europe. Sites that have experienced the largest declines in total abundance and/or species richness also show larger declines in acoustic diversity and sound intensity. However, it is important to note that the initial structure of each bird community, together with how the characteristics of individual songs and calls complement each other, also plays an important role. Ongoing declines in bird populations are expected to cause further reductions in attributes of soundscape acoustics and, by extension, a continued decline in the quality of our experience of the natural world.

This study in the Scottish uplands shows that cessation of grazing which results in more uniform tall ground vegetation leads to Whinchats breeding at higher elevations. Whinchats prefer ground vegetation with a varied structure and these changes result in them heading to higher ground where the environment can prove to be too harsh for them.

New research from BTO has used GPS tracking to investigate the feeding preferences of breeding Herring Gulls at a declining colony, and found that these birds are more likely to be foraging on Mussels than pilfering your lunch. Despite their fearsome reputation, breeding Herring Gull numbers are declining at many formerly important sites and this species has been on the Birds of Conservation Concern Red List since 2009. New research by BTO has used GPS tracking to investigate the movements of Herring Gulls breeding at South Walney, Cumbria. Declines at this well-studied colony mean breeding numbers are currently approximately a tenth of those counted in the late 1980s, when the colony peaked at approximately 11,000 apparently occupied nests. Approximately 75% of fixes from the GPS tags attached to the 24 individuals tracked came from intertidal and near-shore habitats, and in particular Mussel beds, when birds were away from the breeding colony. It is likely that birds were visiting these areas to feed. Previous studies of Herring Gulls breeding at South Walney had shown the importance of landfill as a food source, but local tips have since closed, likely contributing to the reduction in the colony's size. Interestingly, none of the tracked birds specialised in foraging in urban habitats, so are not likely to come into conflict with humans in this environment, where they can be perceived as a pest. However, the birds' specialisation on Mussel beds shows the importance of managing shellfisheries in a way that meets the needs of both humans and Herring Gulls in order to mitigate further declines at this colony.