Status and trends

Completeness of this information varies among species depending on their frequency of occurrence and whether we receive enough information to robustly quantify status and trends. 

Information is presented under a number of headings:

• Conservation status
• Population size
• Population change
• Distribution
• Distribution change
• Seasonality

Conservation status

In this section, we provide information on the species’ conservation or threat status and whether it is afforded protection under national and international legislation. 

The conservation status of the species is given at three levels: United Kingdom, European and Global.

United Kingdom

The conservation status of 246 regularly occurring birds in the U.K. has been reviewed by the leading governmental and non-governmental conservation organisations (Stanbury et al. 2021). This resulted in each species being placed on one of three lists in Birds of Conservation Concern in the United Kingdom, Channel Islands and Isle of Man: Red, Amber or Green. 

• Red List species are those which are: Globally Threatened, whose population or range has declined rapidly in recent years, or that have declined historically and not shown a substantial recent recovery. 
• Amber List species are those which have an unfavourable conservation status in Europe, whose population or range has declined moderately in recent years or whose population has declined historically but made a substantial recent recovery. It also includes rare breeders and those for which the UK holds internationally important or localised populations. 
• Green List species fulfil none of the above criteria and are of least conservation concern. 

Read more on the details of the criteria and how they were applied. 

Europe

The conservation status of birds in Europe is based on the application of IUCN red listing criteria (see below) at the regional (continental) level. The European Red List of Birds was published in 2021 and was compiled by BirdLife International. 

Global

Species of global conservation concern are assessed by the International Union for Conservation of Nature and Natural Resources (IUCN) to "identify and document those species most in need of conservation attention if global extinction rates are to be reduced".

Species of concern are placed on a global Red List, according to internationally accepted criteria (IUCN 2001). The primary categories, with an indication of the qualifying criteria, are:

• Critically Endangered: A rapid population decline in the last 10 years, an extremely restricted range or very low population size and so faces an extremely high risk of extinction in the wild.
• Endangered: Population decline of >50%, a restricted range or low population size and so faces a very high risk of extinction in the wild.
• Vulnerable: Population decline of >30%, a limited range or small population size, so the population faces a high risk of extinction in the wild.
• Near Threatened: A species which does not qualify for either of the three categories above, but which is close to doing so, or is likely to do so in the near future.
• Least Concern: Species which do not fulfil the above criteria are considered of Least Concern
• Data Deficient: Species for which information is relatively limited are highlighted as Data Deficient.
• Extinct: Reserved for species for which there is no reasonable doubt that the last individual has died.

See the IUCN Criteria for a full explanation of the qualifying criteria for each category.

Legal coverage

Details of UK and EU legislation under which the species is specifically protected. In the UK most species receive general protection under the Wildlife & Countryside Act (1981), the EU Wild Birds Directive (EC/79/409)and the Bern Convention on Conservation of Wildlife & Habitats ('Habitats' Directive).

The Bonn Convention provides protection for migratory species in general, and waterbirds in particular under the African-Eurasian Waterbird Agreement. In each case the Schedule the species is listed on is given, asterisks indicate that listing is restricted in some way, either to a particular populations or race, or to a particular part of the schedule.

If a UK Biodiversity Action Plan (BAP) has been drawn up, this is noted (together with Contact Organisation and Lead Partners, as of January 2006).

Wildlife and Countryside Act

The WCA aims to protect wildlife by prohibiting the killing or taking of animals. The Schedules under which birds are specifically listed are:

• Schedule 1: Birds which are protected by special penalties.
• Schedule 2: Birds which may be killed or taken.
• Schedule 3: Birds which may be sold.
• Schedule 4: Birds which must be registered and ringed if kept in captivity
• Schedule 9: Non-native species not to be released into the wild

Wild Birds Directive

The WBD aims to protect wild birds and their habitats throughout Europe, in part through the designation of Special Protection Areas (SPA). Amendments up to September 2003 are included.

• Annex I: The directive requires these species to be the subject of special conservation measures concerning their habitat in order to ensure their survival and reproduction
• Annex II: These species may be hunted, though hunting of some species is limited to particular countries
• Annex III: For these species 'trade activities' shall not be prohibited; trade in all other species is prohibited.

Bern Convention

The Convention on the Conservation of European Wildlife and Natural Habitats aims to maintain populations of wild fauna and flora with a particular emphasis on endangered species. Amendments up to March 2002 are included.

• Appendix II: Lists strictly protected species.
• Appendix III: Lists protected species.

Bonn Convention

The Convention on the Conservation of Migratory Species of Wild Animals aims to provide a framework for the conservation of migratory species and their habitats by means of protection and the conclusion of international agreements. Amendments up to December 2002 are included.

• Appendix I: Lists species in danger of extinction throughout all or major parts of their range.
• Appendix II: Lists species which would benefit from international cooperation in their conservation and management.

African-Eurasian Waterbird Agreement

AEWA is a daughter agreement to the Bonn Convention that aims to conserve migratory waterbirds through coodinated measures across the flyway. Those species to which the agreement applies are listed here. Amendments up to September 2002 are included.

Convention on International Trade in Endangered Species of Wild Fauna and Flora

CITES aims to ensure that international trade in wild animals and plants does not threaten their survival. Amendments up to October 2003 are included.

• Appendix I: Species threatened with extinction, international trade is prohibited.
• Appendix II: Species that may become threatened with extinction if trade is not closely controlled, the Appendix also includes some 'look-alike' species.

Natural Environment and Rural Communities (NERC) Act 2006

The Natural Environment and Rural Communities (NERC) Act came into force on 1st Oct 2006. Section 41 (S41) of the Act requires the Secretary of State to publish a list of habitats and species which are of principal importance for the conservation of biodiversity in England.

The S41 list is used to guide decision-makers such as public bodies, including local and regional authorities, in implementing their duty under section 40 of the Natural Environment and Rural Communities Act 2006, to have regard to the conservation of biodiversity in England, when carrying out their normal functions.

• Section 41: These are the species found in England which were identified as requiring action under the UK BAP and which continue to be regarded as conservation priorities under the UK Post-2010 Biodiversity Framework.

Population size

United Kingdom population size estimates are generally given for the breeding season or winter period, sometimes for passage period if that is the key period when the species occurs in the UK.

For resident species e.g. Blue Tit, we show the breeding population size. For species where status changes markedly between seasons, such as migratory waterbirds e.g. Oystercatcher, we give both breeding and wintering population estimates. 

• Breeding population sizes are mostly taken from Woodward et al. (2020), which represents the work of the Avian Population Estimates Panel and refers specifically to Great Britain (i.e. excluding Northern Ireland and the Isle of Man). An indication of the reliability of the estimate is given on a three point scale (Good, Moderate or Poor). For an earlier assessment of population sizes see Baker et al. (2006).
• Winter population sizes are also taken from Woodward et al. (2020). For waders and waterfowl these are the mean annual peak count from the Wetland Bird Survey (WeBS). Estimates for a few other species are given where the species occurs mostly in winter and a reaonably reliable estimate of population size is available. For selected (mostly sedentary) species we have made a rough guess at the peak winter population size by taking the breeding population size and adding a fraction (number of broods * brood size * juvenile survival) for the years productivity; these figures are intended as a rough guide and should be used with extreme caution!
• Passage population sizes are taken from Fraser & Rogers (2001) and represent the annual mean number of birds reported over the period 1990-1999. These figures rely on records submitted to county bird reports, so are likely to underestimate the true total somewhat. In general, spring and autumn passage are not equal in size, with the autumn passage of birds usually being much larger and so contributing most to the total. These estimates refer just to Britain.

BOU category

The list of species officially recorded in Great Britain is maintained by the British Ornithologists' Union. In 1997, the categorisation was revised to assist protection under national wildlife legislation, especially of naturalised species.

Categories A, B and C are included in the British list, Categories D and E are not.

• A Species that have been recorded in an apparently natural state at least once since 1 January 1950.
• B Species that were recorded in an apparently natural state at least once between 1 January 1800 and 31 December 1949, but have not been recorded subsequently.
• C Species that, although introduced, now derive from the resulting self-sustaining populations. 
  • C1 Naturalised introduced species – species that have occurred only as a result of introduction, e.g. Egyptian Goose Alopochen aegyptiacus
  • C2 Naturalised established species - species with established populations resulting from an introduction by humans, but which also occur in an apparently natural state, e.g. Greylag Goose Anser anser.
  • C3 Naturalised re-established species - species with populations successfully re-established by humans in areas of former occurrence, e.g. Red Kite Milvus milvus.
  • C4 Naturalised feral species - domesticated species with populations established in the wild, e.g. Feral Pigeon Columba livia.
  • C5 Vagrant naturalised species - species from established naturalized populations abroad, e.g. possibly some Ruddy Shelduck Tadorna ferruginea occurring in Britain. There are currently no species in category C5.
  • C6 Former naturalised species – species formerly placed in C1 whose naturalized populations are either no longer self-sustaining or are considered extinct, e.g. Lady Amherst's Pheasant Chrysolophus amherstiae. 
• D Species that would otherwise appear in Category A except that there is reasonable doubt that they have ever occurred in a natural state. Species placed in Category D only form no part of the British List, and are not included in the species totals.
• E Species that have been recorded as introductions, human-assisted transportees or escapees from captivity, and whose breeding populations (if any) are thought not to be self-sustaining. Species in Category E that have bred in the wild in Britain are designated as E*. Category E species form no part of the British List (unless already included within Categories A, B or C).
• F Records of bird species recorded before 1800. 

Population change

Population Change concerns how the number of birds in the UK has changed over time. 

For all species routinely monitored in the breeding season and/or in winter, we present the long-term UK population change. These are usually expressed as percentage increase or decrease over some period, for example a 29% increase over the period 1967 to 2020.

The source of the change statistic is given in the book icon next to the change estimate. Breeding season changes are usually derived from the Common Bird Census and the BTO/JNCC/RSPB Breeding Bird Survey, whilst winter changes are available for waterbirds from the BTO/RSPB/JNCC Wetland Bird Survey. Both surveys rely on volunteers surveying selected sites.

Distribution

Distribution concerns where a species may be encountered, which may be expressed geographically as a map, or with respect to the habitats in which a species occurs. 

Maps and occupied 10-km squares

BTO and its partners periodically conduct atlas projects which aim to map where all species breed and winter in Britain and Ireland. The last atlas was the Bird Atlas 2007–11 project, which mapped breeding distributions based on volunteer fieldwork during 2008–11, and winter distributions based on volunteer fieldwork during the winters 2007/08 to 2010/11.

For all species recorded during these periods a distribution map is shown in BirdFacts, indicating the geographical spread of 10-km squares occupied by each species. Alongside this we also present the number of 10-km squares occupied in the UK (and the percentage of available squares occupied).

European distribution map

For species that breed in Europe, we provide a link to the European Breeding Bird Atlas website where you can plot the distribution of species across Europe.

Breeding season habitats

For common and widespread breeding species we give the habitat in which the species is most frequently recorded, and other habitats in which it is common. This information is derived from the BTO/JNCC/RSPB Breeding Bird Survey in which habitat is recorded in each of ten transect sections in a 1-km square, according to the hierarchical classification of Crick (1992).

For these purposes, we generally only consider the top two levels of codes, and we have amalgamated some categories (see below). We consider birds using terrestrial and aquatic habitats separately and used data from 2000–2003.

For each year, the proportion of all transect sections of each habitat type occupied by a species was calculated. Proportional occurrence in each habitat was then scaled (divided) by the occurrence in the most frequent habitat, so habitat occurrence ranges from 0 (absent) to 1 (in the most frequently occupied habitat) for all species, irrespective of how abundant they are.

These scaled values were then averaged across the three years considered (2000, 2002, 2003; no data were available for 2001) and assigned to three categories.

• Most frequent habitats: scaled proportional occupancy >= 0.95
• Also common in habitats: scaled proportional occupancy >= 0.7
• And found in: scaled proportional occupancy >= 0.5

Thus, for each of the habitats listed a bird is at least half as likely to occur there as it is in the habitat in which it is commonest.

Habitat description using BTO habitat codes

Terrestrial Species

• Towns F1, F2 (includes urban and suburban areas)
• Villages; F3 (areas of more scattered dwellings) 
• Deciduous Wood A1, A4 (woodland is more than 5m tall) 
• Coniferous Wood A2, A5 (woodland is more than 5m tall) 
• Scrub B1-B7 (shrubs or young trees <5m tall)
• Arable Farmland E4
• Pasture Farmland E1, E2 (improved or unimproved, enclosed)
• Moorland C2, C3 (usually unenclosed, upland grazing)
• Bog D4, D6, D7 (waterlogged peat, with Sphagnum Grass)
• Heath C1, C4, C5, D1, D5 (dry semi-natural grass, low-lying) 
• Marsh C6, C8, D2
• Reedbed C7
• Coastal Habitat C9, H1-H5

Aquatic species

• Estuaries C9, H3, H4 (incl. saltmarsh & brackish lagoons) 
• Open Shore H1, H2, H5
• Along Streams G6, G8 (rivers and ditches <2m wide) 
• Along Rivers G7, G9, G10 (rivers and ditches >2m wide) 
• Lakes G3, G4 larger than 450m2 (~2 tennis courts)
• Ponds G1, G2, G5 (smaller than 450m2 and gravel pits)

Relative frequency by habitat

For common and widespread breeding species the graph shows the relative use of different habitats. See the previous section for the source and derivation of these values.

Distribution change

Distribution Change concerns how the geographical pattern of distribution of a species has changed over time. 

Map and change in occupied 10-km squares in the UK

BTO and its partners periodically conduct atlas projects which aim to map where all species breed and winter in Britain and Ireland. Volunteers conducted breeding atlas fieldwork in the spring–summer periods of 1968–72, 1988–91 and 2008–11. In winter, atlas fieldwork was conducted in the winter periods of 1981/82 to 1983/84 and 2007/08 to 2010/11.

For species recorded during these periods, it is possible to produce maps showing 10-km squares that were occupied in an early (e.g. 1968–72) and a later atlas period (e.g. 2008–11). These can be thought of as areas of ‘stable’ occupancy and are labelled as ‘Present both’ on the maps. The 10-km squares where the species has apparently colonised between atlases are labelled as ‘gains’ on the map, and those where the species has apparently disappeared are labelled as ‘losses’.

The geographical pattern can be summarised as an overall range change statistic, indicating the overall change in the number of occupied squares, usually expressed as a percentage. For example, the Blue Tit winter range expanded by 3.4% from 1981/82–1983/84 to 2007/08–2010/11. 

Seasonality

Seasonality concerns how aspects of a species status or biology vary through the year. Examples are the timing of breeding, feather moult and migration. 

The graph shows the times of year when a species can be detected in the UK. Taller bars indicate periods when the species is more likely to be detected. For migratory species these graphs show when the species arrives and departs. Seasonal variation can also be caused by changes in behaviour that make a species more or less easy to detect.

For example, some species are more easily detected in spring when singing e.g. Meadow Pipit, or in autumn when migrating e.g. Skylark. The graph is based on complete lists submitted to BTO’s BirdTrack portal. Birdwatchers submit lists of all the species they see during an outing. By indicating the list is complete we can infer that some species weren’t detected. Using these data we can determine the percentage of lists submitted in a period on which a species was recorded, a metric referred to as the ‘reporting rate’.

garden_warbler_seasonality_plot.png

Seasonality plot for Garden Warbler, a summer visitor

The shaded boxes show that the earliest Garden Warblers arrive in mid March, with the last individuals lingering until late October. Although some Garden Warblers are present over that extended period, the bars based on reporting rates indicate that birds begin to arrive in number from mid April, with detections peaking in May when birds are in full song; at that time around 10% of birdwatching trips included Garden Warblers. Detections then tail off, as birds are harder to detect during nesting and on autumn migration. 

References

• Crick, H.Q.P. 1992. A bird-habitat coding system for use in Britain and Ireland incorporating aspects of land-management and human activity. Bird Study 39:1–12.
• Fraser, P.A. & Rogers, M.J. 2001. Report on scarce migrant birds in Britain in 1999. British Birds 94: 560–589.
• IUCN 2001. Red List categories and criteria, version 3.1. IUCN, Gland, Switzerland.
• Stanbury, A.J., Eaton, M.A., Aebischer, N.J., Balmer, D., Brown, A.F., Douse, A., Lindley, P., McCulloch, N., Noble, D.G. & Win, I. 2021. The status of our bird populations: the fifth Birds of Conservation Concern in the United Kingdom, Channel Islands and Isle of Man and second IUCN Red List assessment of extinction risk for Great Britain. British Birds 114: 723–747.
• Woodward, I., Aebischer, N., Burnell, D., Eaton, M., Frost, T., Hall, C., Stroud, S. & Noble, D. 2020. APEP 4 - Population estimates of birds in Great Britain and the United Kingdom. British Birds 113: 69–104.