Five seabird species are added to the Birds of Conservation Concern Red List in this addendum to the 2021 update, bringing the total number of Red-listed seabird species to 10, up from six since seabirds were last assessed. The Amber List of seabirds moves from 19 to 14 species, and the Green List increases from one to two species.

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

The UK has lost seven species of breeding birds in the last 200 years. Conservation efforts to prevent this from happening to other species, both in the UK and around the world, are guided by species’ priorities lists, which are often informed by data on range, population size and the degree of decline or increase in numbers. These are the sorts of data that BTO collects through its core surveys. For most taxonomic groups the priority list is provided by the International Union for Conservation of Nature (IUCN) – the IUCN Red List comprises roughly 12,000 species worldwide and their conservation status. However, for birds in the UK, most policy makers refer to the Birds of Conservation Concern (BoCC) list, updated every six years (most recently in 2015). A new study funded by the RSPB and Natural England in cooperation with BTO, WWT, JNCC, and Game & Wildlife Trust has carried out the first IUCN assessment for birds in Great Britain. The study applied the IUCN criteria to existing bird population data obtained from datasets like the BTO/JNCC/RSPB Breeding Bird Survey (BBS). The criteria take into account various factors, most notably any reduction in the size (both in abundance and range) of populations, loss of habitats key to the species, small or vulnerable population sizes, and extinction risk. Alongside this, the criteria look to see if there is a “rescue” effect – such as immigration from neighbouring populations that might boost the population’s numbers, reducing the risk of extinction. The species are then categorised into one of the threat levels below. The results of the new study show that a concerning 43% of regularly occurring species in Great Britain are classed as Threatened, with another 10% classified as Near Threatened. Twenty-three breeding or non-breeding populations of birds were classed as Critically Endangered, including Fieldfare and Golden Oriole (both possibly extinct as breeders), Whimbrel, Turtle Dove, Arctic Skua and Kittiwake, as well as non-breeding populations of Bewick’s Swan, White-fronted Goose and Smew., Over the past 200 years, seven species have gone extinct as breeders in Britain, including Serin, Temminck’s Stint and Wryneck in the past 25 years. The total percentage of threatened birds in Great Britain (43%) is high compared to that seen elsewhere in Europe (13%). Reasons for this are not entirely clear, although it may be that Britain’s island status has something to do with this, as there are fewer neighbouring “rescue” populations. Although the results from the IUCN assessment and BoCC assessment largely overlap, the IUCN assessment raises the level of concern for species such as Red-Breasted Merganser, Great Crested Grebe, Moorhen, Red-Billed Chough (all classed as Vulnerable), and Greenfinch (Endangered). These species might thus warrant closer monitoring in the near future. In contrast, the BoCC assessment identifies a number of species of concern whose declines have been more gradual but over long time periods (e.g. Skylark and House Sparrow). The authors emphasise that this assessment is not a replacement of the BoCC report, but rather that the two reports complement each other. With this new wealth of knowledge, there will hopefully be even more support for those species that need it most.