It provides a single, comprehensive source of information on the current status and distribution of waterbirds in the UK for those interested in the conservation of the populations of these species and the wetland sites they use. Data from this edition of Waterbirds in the UK provide further evidence that wintering ducks, geese, swans and waders are adapting to climate change by altering their migration.

Understanding the habitat requirements of Short-eared Owls can inform conservation action for this species. Given the vast distances that individual Short-eared Owls can travel over the course of a season, we need to understand how these requirements may vary between locations. A substantial proportion of Britain’s Short-eared Owl population breeds on managed moorland, where these avian predators specialise on small mammal prey. Such moorland is widely managed for Red Grouse through the control of predators and the burning of vegetation, practices which can be controversial. Efforts to increase or restore heather and other dwarf-shrub cover, which are seen by many as a conservation priority, may also alter the nature of the moorland habitat used by Short-eared Owls. Set against this background, it has become especially pertinent to understand how Short-eared Owls use moorland habitats and, in particular, the different vegetation types present. Because of their nomadic behaviour, there is also a need to understand how these birds use similar open habitats elsewhere. This tracking study, which involved 17 fully-grown Short-eared Owls tagged with GPS tracking devices in Scotland between 2017 and 2020, provided an opportunity to look at individual habitat use across the different sites used by these birds in Scotland, England and Norway. The study looked at habitat use within individual home ranges, i.e. those areas used by the birds for more than five consecutive days and which were less than 500 hectares in size. Locations within 50 m of nest sites were excluded from the analysis because females may continuously incubate eggs or brood small chicks, skewing attempts to understand habitat use. Relative to their availability, there was a tendency for Short-eared Owls in Britain to preferentially use areas of grassland, including those smaller patches located within a wider Heather-grassland mosaic. In contrast, the tracking data from those individuals that also spent time in Norway revealed a tendency to hunt more over dwarf shrubs. The dwarf shrub community in Norway is more diverse than here in Britain, both in terms of species composition and structure. Such differences are likely to reflect prey availability, but they also highlight the behavioural plasticity of these birds. The results of this work can be used to inform relevant conservation strategies in at least three different ways. They inform the habitat management of specific sites, highlight landscapes towards which targeted management could be directed, and identify specific sites for conservation designation, protection and management.

The Seabird Monitoring Programme, funded by the British Trust for Ornithology and Joint Nature Conservation Committee (JNCC), in association with the Royal Society for the Protection of Birds, aims to ensure that sample data on seabird breeding numbers and breeding productivity are collected both regionally and nationally, for 25 species of seabird that regularly breed in Britain and Ireland, to enable their conservation status to be assessed.

The report includes detailed information about the population trends and breeding success of seabirds in Northern Ireland, over the 2023 breeding season. Notably, Fulmar and Kittiwake populations are reported to be experiencing continued declines, while Guillemot, Common Gull and Herring Gull populations show increases at most breeding sites. Low productivity was reported in Black-headed Gulls, Sandwich Terns and Common Terns, likely due to the impacts of highly pathogenic avian influenza (HPAI). Although Black-headed Gulls make up the majority of confirmed HPAI mortality cases in Northern Ireland in 2023, other birds significantly affected include terns, Kittiwakes and auks. A contributor report about HPAI in Northern Ireland by Ronan Owens (Higher Scientific Officer, DAERA, NIEA) details developments in environmental organisations’ responses to HPAI in 2023, including cross-sector communication, improved surveillance and monitoring of HPAI impacts, and improved online systems for the public to report dead birds. Monitoring reports for Strangford Lough and the Outer Ards are included, as well as several additional contributor articles: Copeland gull censuses, by Roisin Kearney (Assistant Conservation Officer, RSPB). The Copeland Islands host one of the largest mixed gull colonies in Northern Ireland, with significant numbers of Lesser Black-backed Gulls and Herring Gulls. The annual gull census was established in 2018; the article details the refinement of the methodology to date as well as the census results so far. Manx Shearwater tracking, by Patrick Lewin (DPhil Student, OxNav, Dept. of Biology, University of Oxford). Tracking the Manx Shearwaters that breed on Lighthouse Island (one of the three Copeland Islands) began in 2007. The article describes the history of tracking Manx Shearwaters from Copeland, including recent advances in technology that have allowed the tracking of fledgling birds as well as adults of breeding age, and the impact of this research on the conservation of shearwaters. Puffin surveys on Rathlin, by Ric Else (Life RAFT Senior Research Assistant, RSPB). Rathlin Island hosts Northern Ireland’s largest seabird colony. The response of seabirds to the removal of introduced Ferrets and Brown Rats from Rathlin is currently being monitored, with a particular focus on Puffins. These birds are especially vulnerable to mammalian predators because of their burrow nests. The article describes the challenges associated with calculating a population estimate, monitoring productivity and mapping the distribution of this species, and how these are being addressed in seabird surveys on Rathlin.

Accumulation of plastic and waste contamination in the natural environment is a growing problem, but little is known of the role animals play in transporting plastics (a process known as ‘biovectoring’) particularly to inland waters and habitats. This study used diet sampling, population monitoring and GPS tracking data of Lesser Black-backed Gulls to monitor the transport of plastics and anthropogenic debris from landfills to an inland reservoir in Spain. The study, led by the Institut de Ciències del Mar and Estación Biológica de Doñana, CSIC, Spain, used diet samples collected in January 2022 at the Fuente de Piedra – an inland lake in Spain that is internationally important for biodiversity. Monthly counts of Lesser Black-backed Gulls were carried out to assess the numbers of birds present at the lake. GPS tracking data collected from studies across Northern Europe, including some led by BTO, were used over 12 ‘winters’, between January to March 2010–22, to understand the spatial movements of individual birds in the local region, coinciding with when birds are either on wintering grounds or on migration. The authors found that a high proportion (94%) of material regurgitated by gulls contained human-related material such as glass and textiles and 86% contained plastics, whereas only 1% plastic mass was present in faeces. Numbers of Lesser Black-backed Gulls at the lake were highest in January, peaking at a maximum count of 33,000 in January 2020. Agricultural habitats were most frequently used by gulls (88% time) as well as three landfill sites in the local area, with some landfills visited more than others, linked to use of bird deterrence measures. A total of 77% of the tracked birds visited at least one of the three landfills on a given day. The authors estimated that, on average, the annual deposition of plastic and other debris by the wintering gull population into the lake was 1,888 g per day, meaning that 400 kg of plastic were estimated to be deposited into the lake each winter, though only ca. 5 kg were from faeces. This study sheds new light on the importance of gulls for biovectoring within ecosystems, and the leakage of plastic and debris from landfills into inland waters. The plastics can accumulate in sediments and become incorporated into food webs, presenting a global contamination issue that needs addressing. The study further highlights the importance of adopting initiatives to tackle the problem, such as waste separation and plastic reduction measures, and bird-deterrence to reduce ingestion by birds at source.

BTO-led research highlights the importance of the quality of protected areas in their effectiveness.