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.

Satellite-tracked male Cuckoos show higher fidelity to sites used during the breeding season than to sites used at other times of the year.

Tracking the long-distance migrations of Arctic Skuas from their north-east Atlantic breeding grounds revealed complex migration strategies, with mixing of individuals from different populations at important staging areas before the birds reached their southern wintering grounds. Arctic Skuas are long-distance migrant seabirds that have seen large declines in breeding numbers across areas of the north-east Atlantic. Part of these declines has been attributed to poor food availability during the breeding season, exacerbated by predation from Great Skuas, particularly in years where food availability is low. However, Arctic Skuas only spend around a third of the year at their breeding grounds. Therefore, they likely also face a range of threats during the non-breeding season. To shed light on the migration routes and strategies of Arctic Skuas, researchers, including BTO scientists, tracked 131 individuals with small tracking devices called geolocators between 2009 and 2019, collecting information from four breeding populations: Scotland, the Faroe Islands, Norway and Svalbard. This collaboration revealed extensive mixing of Arctic Skuas from different breeding populations during migration in several discrete staging areas. An area of high marine productivity, part of which has recently been designated as a high seas Marine Protected Area, was particularly important to the skuas during both their south-bound (autumn) and north-bound (spring) migrations. Because of their predictable food sources, such staging areas are vital, fuelling long flights to the wintering areas and, during spring, enabling individuals to build up reserves for the upcoming breeding season. This considerable mixing of individuals means that if adverse conditions affect the skuas in these important staging areas, then it has the potential to negatively impact multiple breeding populations through reduced survival or productivity. However, the data also revealed some differences in the migration routes and staging areas of individuals from the different breeding populations. Specifically, during southbound migration, skuas from Scotland largely migrated south through the North Sea and along the Iberian Peninsula, whilst those from the other more northerly populations tended to head west towards the mid-Atlantic staging area. Individuals from Svalbard staged much further west in the Atlantic during both migrations, where they may have encountered different, potentially more favourable, conditions given that the Svalbard population appears to be declining less severely than other populations in the north-east Atlantic. Understanding where long-distance migrants, such as Arctic Skuas, are distributed during migration and the strategies they use is a vital first step in identifying threats that individuals may encounter en route, and how this may affect their survival, productivity and therefore population trends. This new knowledge will help us prioritise future research and conservation actions for this declining charismatic seabird. View the Press release associated with this publication

Seabird populations face many different challenges, from the impacts of a changing climate through to the risks posed by offshore wind farms. Understanding how environmental conditions influence seabird distributions at sea, and therefore interactions with potential threats, at the individual level, can help improve our understanding of the population-level impacts of these challenges. During the 2021 breeding season, BTO scientists tracked 20 Kittiwakes, fitted with small GPS devices, from Whinnyfold – part of the Buchan Ness to Collieston Coast Special Protection Area – in Aberdeenshire. There are several existing offshore wind farms within the vicinity of this Kittiwake colony, with several more proposed for the future. The study found no evidence of habitat selection when averaging across all individuals tracked, with large uncertainty in how the environmental conditions (proxies of prey availability, and including sea surface temperature, sea depth, and the presence and location of ocean fronts) were linked to where the Kittiwakes foraged. Instead, the results revealed considerable variation among individuals. This was not only in the response of individuals to local environmental conditions, but also in the extent to which they visited areas where wind farms had either already been built or are proposed. However overall, the amount of time spent by individual birds within the existing and proposed offshore wind farms’ footprints was relatively low. The study’s results emphasise the importance of understanding individual variation when measuring the impact of specific pressures on Kittiwake, and other seabird populations. By averaging across individuals to focus on population responses, we may be under- or overestimating the impact of potential threats, such as offshore wind farms, on some individuals. This could lead to potential unforeseen consequences on demographic rates, such as survival and breeding success, especially where individual differences are driven by factors such as sex, age or breeding stage.