New research from a collaboration between BTO, Natural England and researchers at the University of Exeter has used GPS-tracking to investigate the movement behaviour of Lesser Black-backed Gulls in response to landfill closures. Gulls were found to increase their foraging effort and switch to alternative habitats following the loss of this important food resource. During the 20th century, gull populations across the globe increased rapidly in response to human activities, with the availability of waste food in landfill sites a key driver of their success. However recently, some gull populations have declined, particularly at formerly large coastal colonies, with the closure of tips likely a contributing factor. Previous gull studies have shown reductions in reproductive performance and changes in diet following landfill closures. However the implications for the birds’ movements have not previously been studied. This research used GPS-tracking data from adult Lesser Black-backed Gulls breeding at two colonies within Special Protection Areas where the species is a designation feature – South Walney, Cumbria and Ribble Marshes, Lancashire – to investigate changes in movement behaviour following the closure of major landfill sites within the birds’ foraging range. In the year after the landfills closed, breeding gulls increased their foraging effort as they had to travel further and for longer on foraging trips. They also switched to alternative foraging habitats. Gulls breeding at South Walney increased their selection of agricultural areas following landfill closures, whilst birds breeding at Ribble Marshes foraged more in nearby towns and cities. Although the long-term consequences of landfill closures for Lesser Black-backed Gulls are unclear, these results highlight how the availability of anthropogenic resources far outside protected areas may influence gull movement behaviour, highlighting the importance of spatial scale when attempting to conserve and manage highly mobile species like gulls. In the short term, gulls responded to landfill closures by switching to forage either in agricultural areas or urban habitats. These habitat switches may alter the location of human-gull conflicts, as foraging gulls in agricultural areas may steal livestock food while those in towns and cities engage in perceived nuisance behaviours such as fouling, littering and food-snatching, potentially requiring management interventions. Finally, this study highlights the value of technology such as GPS-devices as a tool to monitor rapid behavioural responses of birds to future environmental change.

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.