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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

December 2021

December 2021

DOI:10.13140/RG.2.2.35668.73602

Authors:

Andrew Stanbury

The Royal Society for the Protection of Birds

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The 5th version of Birds of Conservation Concern reviews the status of all regularly occurring birds in the UK, Channel Islands and Isle of Man. Breeding and overwintering bird species have been assessed against a set of objective criteria and placed on the Green, Amber or Red lists to indicate their level of conservation concern.

Annual bag index (± 95% confidence limits) for Ptarmigan Lagopus muta in Scotland, 1961-2019, from GWCT's National Gamebag Census.

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Proportion of species allocated to the Red, Amber and Green lists in BoCC5, overall and split into different groupings. Groupings largely based around HBW & BirdLife International (2020) families.

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Former regularly breeding species in the UK, with status from previous BoCC reviews. Species are placed on the Red (R) or Amber (A) lists, or identified as a former breeder (FB).

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723

Alan Harris

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

Andrew Stanbury, Mark Eaton, Nicholas Aebischer,

Dawn Balmer, Andy Brown, Andy Douse, Patrick

Lindley, Neil McCulloch, David Noble and Ilka Win

Common Swifts Apus apus

Abstract The fifth review of Birds of Conservation Concern (BoCC5) in the UK,

Channel Islands and Isle of Man assessed and assigned 245 species to updated Red,

Amber and Green lists of conservation concern and showed a continuing decline

in the status of our bird populations. In total, 70 species (29% of those assessed)

are now on the Red list, up from 36 species in the first review in 1996. Since the

last review, in 2015, Golden Oriole Oriolus oriolus has been lost as a breeding

species. Eleven species have been moved to the Red list, while only six species

moved from Red to Amber. Newly Red-listed species include Common Swift Apus

apus, House Martin Delichon urbicum, Greenfinch Chloris chloris and the globally

threatened Leach’s Storm-petrel Oceanodroma leucorhoa. There has been no

724 British Birds 114 • December 2021 • 723–747

Introduction

Regular assessments of status are crucial aids

in identifying species and habitat conserva-

tion priorities, enabling us to target finite

resources most effectively. The first formal

assessment for UK birds listed 117 species

(Red Data Birds in Britain, Batten et al.

1990). Since then, a process for identifying

priority species has become well established:

Birds of Conservation Concern (BoCC), which

uses quantitative assessments against stan-

dardised criteria to allocate species to Red,

Amber or Green lists depending on their

level of conservation concern. Gibbons et al.

(1996a; BoCC1) were the first to adopt this

traffic-light system. Since then, the BoCC

process has been repeated at regular intervals,

by Gregory et al. (2002; BoCC2), Eaton et al.

(2009; BoCC3) and Eaton et al. (2015;

BoCC4). All of these reviews have used the

same approach to establish priorities,

although there have been some changes in

the details of methodology to reflect growing

experience and changes in data availability.

These reviews have documented the

declining status of UK bird populations, with

a progressive lengthening of the Red list,

from 36 species in BoCC1 to 67 in BoCC4.

BoCC1 raised the profile of the widespread

decline of farmland birds, while subsequent

reviews have highlighted other topics of

concern, such as the plight of woodland birds

in BoCC2, Afro-Palearctic migrants in BoCC3

and upland birds in BoCC4. The reviews have

also showcased conservation success stories,

such as the recovery, or partial recovery, of

some raptor species and Eurasian Bittern

Botaurus stellaris.

We a r e e x t re m el y f o r tu n a te i n t h e U K t o

have many thousands of dedicated volunteer

Stanbury et al.

birdwatchers, coordinated by professional

research and conservation organisations, col-

lecting information on our bird populations.

As a result, an impressive repository of robust

data, including regularly updated species’

trends, population estimates and range maps,

allow us to undertake detailed assessments

such as BoCC. This level of information is

rarely available for birds elsewhere, or for

other taxonomic groups in the UK or

beyond. Although similar exercises are

carried out in Ireland (Gilbert et al. 2021),

Wales (Johnstone & Bladwell 2016) and the

Isle of Man (Morris & Sharpe 2021), the

BoCC concept is not widely used elsewhere,

so our reviews can rarely be viewed in a

quantitative context beyond birds in the UK.

A more recently developed but now well-

established approach, with many parallels to

our own, is the International Union for

Conservation of Nature (IUCN) Red List

process. In contrast to BoCC, which concerns

conservation in a broad sense, the IUCN

assessment solely concerns extinction risk,

using standardised criteria that can be

applied to assess any plant or animal taxon.

IUCN Red Lists are used to assess the global

status of species (IUCN 2019; www.iucn

redlist.

org), but can also be applied at

regional, national or local scales (IUCN

2012), including the European Red List of

Birds (BirdLife International 2021). The

IUCN approach is used to assess the status of

a broad suite of our native wildlife and, to

date, c. 12,000 species from around 40 taxo-

nomic groups have been assessed Britain-

wide, providing an increasingly detailed

context within which to view the changing

status of our birds. Recognising this, we con-

ducted the first IUCN assessment of bird

improvement in the overall status of species associated with farmland and upland,

or Afro-Palearctic migrants; indeed, more such species have been Red-listed.

Concerns over the status of our wintering wildfowl and wader populations have

also increased. As a direct result of targeted conservation action, White-tailed

Eagle Haliaeetus albicilla has been moved from Red to Amber.

We also present the separate, and distinct, second IUCN Regional Red List

assessment of extinction risk for Great Britain, which shows that 46% of 235 regu-

larly occurring species, and 43% of 285 separate breeding and non-breeding popula-

tions, are assessed as being threatened with extinction from Great Britain.

725

British Birds 114 • December 2021 • 723–747

The status of our bird populations: BoCC5 and IUCN2

populations in Britain in

2017 (IUCN1, Stanbury et

al. 2017).

BoCC thus embraces

factors such as change

over longer periods than

IUCN (notably including

a historical context) and

the international impor-

tance of UK bird popula-

tions. On the other hand,

the IUCN approach

allows different taxo-

nomic groups to be

assessed on a more level

playing field, using

the

same well-established,

internationally recognised

criteria. This allows

changes in status to be

tracked and the potential

creation of multi-taxa indi-

cators (e.g. Red List Index,

Butchart et al. 2005).

Here, we present the

fifth Birds of Conservation

Concern review for the

UK, Channel Islands and

Isle of Man (BoCC5),

alongside the second

IUCN Regional Red List

assessment of extinction

risk for Great Britain

(IUCN2), thereby har-

monising the timings of these two assess-

ments. Our focus is on the current status of

species (up to 2019 or winter 2019/20). The

factors that are driving change in species’

status are covered in detail elsewhere, such

as in the State of Nature reports (e.g.

Hayhow et al. 2019).

We had hoped to incorporate the results

from the latest seabird census, Seabirds

Count, in this review but, owing to delays to

fieldwork caused by Covid-19, this has not

been possible. As there are currently uncer-

tainties around the status of some of our

seabirds, we decided against the inclusion of

most of these species and we shall publish an

addendum after the census results become

available. Thus, the assessment for breeding

seabirds from previous reviews (Eaton et al.

2015; Stanbury et al. 2017) are transcribed

here. The exception to this is Leach’s Storm-

petrel Oceanodroma leucorhoa, as most of

the relevant data for this species are already

available (Deakin et al. in press).

Methods

The BoCC assessment process

The BoCC5 process followed those of pre-

vious reviews, whereby each bird species was

assessed against a set of standardised Red-

and Amber-list criteria, which remained

unchanged since BoCC4 (see below). Species

were placed on the highest priority list for

which they satisfied any criteria. If they met

none of these criteria, they were placed on

the Green list. Breeding species were placed

on the list of ‘former breeders’ if they had not

bred in any of the five most recent years for

which data were available.

461. Leach’s Storm-petrel Oceanodroma leucorhoa, Massachusetts,

USA, August 2015. The St Kilda archipelago, off the coast of northwest

Scotland, holds the vast majority of the UK breeding population of

Leach’s Storm-petrel. Recent surveys here have highlighted a decline of

68% between 2000 and 2019, likely in part due to predation by Great

Skuas Stercorarius skua. This, along with Leach’s Storm-petrel being

classed as Vulnerable globally, has resulted in the species being added

to the Red list and qualifying as Critically Endangered in Great Britain.

Luke Seitz

726 British Birds 114 • December 2021 • 723–747

Red- and Amber-list criteria –colours denote

which list the criterion is applicable to.

IUCN: Global IUCN Red List status. Species

that are globally threatened (Critically

Endangered, Endangered and Vulnerable,

but not Near Threatened) under IUCN

guidelines, as assessed by BirdLife

International, the IUCN Red List Authority

for birds in 2021 (www.iucnredlist.org).

ERLOB: European Red List status. Species

that are threatened (Critically Endangered,

Endangered and Vulnerable, but not Near

Threatened) in Europe under IUCN guide-

lines, as assessed by BirdLife International,

the IUCN Red List Authority for birds, in

2021 (BirdLife International 2021).

HD: Historical decline in breeding populations.

Species judged to have declined severely

between 1800 and 1995, from an assessment

conducted by Gibbons et al. (1996b), and

which have not recovered subsequently.

Species that are deemed to have recovered par-

tially are Amber-listed (see below), or Green-

listed if they have recovered completely.

HDrec: Historical decline – recovery. Species

previously Red-listed for historical decline,

followed by an increase of at least 100% over

25 years or the longer-term period. If, fol-

lowing a move to HDrec, a species increases

by at least 167% from its HDrec level, it no

longer qualifies as HDrec (e.g. would move

to Green if not qualifying under other cri-

teria). Further explanation of this process is

given in Eaton et al. (2015).

BDp/BDMp: Breeding population decline.

Defined as a severe decline of >50%

(BDp), or moderate decline (>25% but

<50% BDMp) in the UK breeding popula-

tion size over either of two assessment

periods: 25 years (BDp1/BDMp1) or the

longer term (BDp2/BDMp2). The latter is

defined as the entire period used for assess-

ments starting in 1969.

WDp/WDMp: Non-breeding population

decline. Defined as a severe decline of

>50% (WDp), or moderate decline (>25%

but <50% WDMp) in the UK population

size over either of two assessment periods:

25 years (WDp1/WDMp1) or the longer

term (WDp2/WDMp2). Non-breeding

trends were assessed only if a species has

substantially independent breeding and

non-breeding populations, otherwise only

Stanbury et al.

the breeding population was assessed. The

same was true for other criteria which could

be applied to both breeding and non-

breeding populations.

BDr/BDMr: Breeding range decline. Defined

as a severe decline in UK range of >50%

(BDr) or moderate decline (>25% but

<50% BDMr) between the breeding bird

atlases in 1988–91 and 2007–11

(BDr1/BDMr1) or 1968–71 and 2007–11

(BDr2/BDMr2), as measured by the calcu-

lated change in the number of occupied

10-km squares.

WDr/WDMr: Non-breeding range decline.

Defined as a severe decline in UK range of

>50% (WDr1) or moderate decline (>25%

but <50% WDMr1) between the wintering

bird atlases 1981–84 and 2007–11, as mea-

sured by the calculated change in the

number of occupied 10-km squares. Since

there are only two wintering bird atlases, it

was not possible to measure range change

over a longer time period.

BR &WR:Breeding and non-breeding rarity.

Species qualified as rare breeders (BR) if the

UK breeding population was <300 pairs, and

as rare non-breeders (WR) if the UK non-

breeding population was <900 individuals.

BL &WL: Breeding and non-breeding local-

isation. Species were considered localised if

more than 50% of the UK population was

found at ten or fewer sites in either the

breeding (BL) or the non-breeding (WL)

season. Sites were defined as either Special

Protection Areas (SPAs; Stroud et al. 2016)

or Important Bird Areas (IBAs; Heath &

Evans 2000). Rare breeders or rare non-

breeders (see above) were not assessed

against this criterion, as their small popu-

lation sizes predispose them to be

restricted to a small number of sites.

BI &WI: Breeding and non-breeding inter-

national importance. Species were consid-

ered of international importance if the UK

holds at least 20% of the European popula-

tion in either the breeding (BI) or the non-

breeding (WI) season. European estimates

were derived from data collated as part of

the ERLOB assessments, but for non-

breeding waterbirds we used estimates for

the flyway populations for northwest

Europe (wildfowl) or East Atlantic (waders)

(CSR8; Wetlands International 2021).

727

British Birds 114 • December 2021 • 723–747

The status of our bird populations: BoCC5 and IUCN2

The IUCN Regional Red List

assessment process

We followed the IUCN’s guidelines for the

application of Red List criteria at regional and

national levels. This regional process com-

prises three stages: 1) identify the taxa to be

assessed; 2) assess the extinction risk faced by

regional populations of each taxon as if in iso-

lation using the global Red List criteria (IUCN

2019); and 3) consider the influence of poten-

tial interactions with populations outside the

region. It is worth noting that the time periods

used for the assessments differ between BoCC

and IUCN. The IUCN assessments are based

around the generation length, mainly multi-

plied by three, of each individual species,

while those of BoCC, for all species, are based

on the last 25 years and a longer time period

(which is determined by data availability).

Generation lengths for species were obtained

directly from BirdLife International (Ian

Burfield pers. comm.). These were recently

reassessed by BirdLife International (e.g. Bird

et al. 2020), so our assessment differs in this

respect from IUCN1.

IUCN Red List criteria

Each species was assessed against the five

standard IUCN Red List criteria (summarised

below). See IUCN (2019) for full details.

! Criterion A: Reduction in the size (either

abundance or range) of the population,

measured over ten years or three

generations, whichever is longer.

! Criterion B: Restricted geographical range

in conjunction with fragmentation,

continuing decline, or extreme population

fluctuations.

! Criterion C: Small population size and

continuing decline.

! Criterion D: Very small population or very

restricted distribution.

! Criterion E: Quantitative analysis of

extinction risk.

Each species was assessed against thresh-

olds for each criterion and its subcriteria,

which, if met or exceeded, qualified it for one

of the standard IUCN Red List threat cate-

gories: Extinct, Regionally Extinct, Critically

Endangered, Endangered, Vulnerable, Near

Threatened and Least Concern. Data

Deficient was used to indicate that a species

was evaluated using available data but this

was found to be insufficient to place the

species into a category. For the Near

Threatened category, which identifies species

not considered formally threatened with

extinction but sufficiently close to be likely to

become so in the near future, we followed the

examples in the guidelines (IUCN 2019; see

Supplementary Online Material (SOM)

https://doi.org/10.5061/dryad.cc2fqz672).

For species that have substantial and at

least partially distinct breeding and non-

breeding populations in Britain (defined as

having a population in the non-breeding

season that is more than twice the size of

the breeding population), notably water-

birds, we assessed breeding and wintering

populations separately.

The final stage of the Regional IUCN Red

List process examines the extent to which

neighbouring populations of the same

species, outside the region, may affect

extinction risk within the region by, for

example, providing a ‘rescue effect’. Under

favourable conditions, such as a continuing

or even increasing flow of immigrants into

the region, it might be appropriate to down-

list the threat category.

Populations qualifying as Critically

Endangered, Endangered or Vulnerable after

this final stage were collectively termed as

‘threatened with extinction’. Where both

breeding and non-breeding assessments were

carried out, we followed the first European

Red List of Birds (BirdLife International 2015)

and the previous Great Britain assessments

(Stanbury et al. 2017) and assigned the

highest threat status from either population

assessment to the species. Further details of

the IUCN assessments are given in the SOM.

Species list

As in previous BoCC reviews (see Eaton et al.

2015), we considered only naturally occurring

species with self-sustaining populations, with

filters to exclude vagrants, defined as species

assessed by the British Birds Rarities

Committee (www.bbrc.org.uk), or species

occurring only as scarce migrants (see e.g.

White & Kehoe 2020a,b). Breeding species

were considered only if they had been proven

(or strongly suspected) to have bred for a

period of at least five consecutive years within

728 British Birds 114 • December 2021 • 723–747

the most recent 25 years for which data are

available. Updating the list on the basis of

these criteria resulted in the addition of Little

Bittern Ixobrychus minutus, Cattle Egret

Bubulcus ibis, Great White Egret Ardea alba

and Black-winged Stilt Himantopus himan-

topus (all appear to have become, or are in the

process of becoming, established regular

breeders), and Yellow-browed Warbler

Phylloscopus inornatus (no longer considered

a scarce migrant). Unlike BoCC4, we did not

include globally threatened species (www.iucn

redlist.org) that have occurred in the UK in

each of the last 25 years, regardless of scarcity

in the UK, resulting in the removal of Aquatic

Warbler Acrocephalus paludicola (assessed in

BoCC1 to BoCC4).

Note that some species were excluded

from assessment as breeding species, but

were assessed because they have larger or

better-established non-breeding populations

(e.g. Red-necked Grebe Podiceps grisegena).

The selection criteria used for IUCN2 were

similar to those for BoCC5, but differed in the

following respects: i) we followed the Regional

Red List recommendation (IUCN 2012) to

exclude colonising species unless they have

bred for ten consecutive years; ii) as with

IUCN1, we applied an optional filter to

exclude species that appear only on passage;

iii) spatial differences between the UK and

Great Britain. As a result, ten species assessed

for BoCC5 were excluded from the IUCN2

assessment: Sooty Shearwater Ardenna grisea,

Great Shearwater A. gravis, Black-winged

Stilt, Curlew Sandpiper Calidris ferruginea,

Little Stint C. minuta, Little Gull Hydrocoloeus

minutus, Long-tailed Skua Stercorarius longi-

caudus, Pomarine Skua S. pomarinus, Snowy

Owl Bubo scandiacus and Short-toed

Treecreeper Certhia brachydactyla.

As with BoCC3 and 4, we conducted a

parallel assessment of the BoCC status of reg-

ularly occurring races of birds in the UK. The

process was as described in Eaton et al. (2009

& 2015) and mirrored the species-level

assessment. As before, the lack of some data

sources at a subspecific level (e.g. Global and

European IUCN assessments, and moni-

toring data at the race level) required us to

create new estimates of populations, trends

and status outside the UK as best we could

with existing data sources. For the first time,

Stanbury et al.

we carried out IUCN assessments for all of

the relevant BoCC races.

Taxon om y in BoCC5 follows HBW &

BirdLife International (2020). Thus, Taiga

Bean Anser fabalis and Tundra Bean Geese A.

serrirostris, Carrion Corvus corone and

Hooded Crows C. cornix and Common

Acanthis flammea and Lesser Redpolls A.

cabaret are treated as single species, with

races assessed separately. For the crows and

redpolls, this represents a change in status

since their assessment in BoCC4. Further

details and results of race assessments in

BoCC5 are given in the SOM.

Data sources

The principal sources of data were the same as

for

previous assessments and described in Eaton

et al. (2009 & 2015), Stanbury et al. (2017), and

in further detail in the SOM. Trend data was

used up to summer 2019, winter 2019/20, or

the most recently available year before then.

The main data sources accessed were:

! The BTO/JNCC Common Birds Census

(CBC) and BTO/JNCC/RSPB Breeding

Bird Survey (BBS) (to 2019).

! The BTO Waterways Bird Survey (WBS)

and BTO/JNCC/RSPB Waterways

Breeding Bird Survey (WBBS) (to 2019).

! BTO/RSPB/JNCC Wetland Bird Survey

(WeBS) and WWT/JNCC/NatureScot

Goose and Swan Monitoring Programme

(to 2019/20).

! The Rare Breeding Birds Panel database

(to 2018).

! Periodic species surveys run under the

Statutory Conservation Agency and RSPB

Annual Breeding Birds Scheme

(SCARABBS), BTO species surveys and

the GWCT/BTO Woodcock survey.

! The three breeding bird atlases (Sharrock

1976; Gibbons et al. 1993; Balmer et al.

2013) and two wintering bird atlases (Lack

1986; Balmer et al. 2013).

! Two sources for seabird monitoring: the

three complete censuses conducted in 1969–

70 (Cramp et al. 1974), 1985–88 (Lloyd et al.

1991) and 1998–2001 (Mitchell et al. 2004),

and the Seabird Monitoring Programme

that has monitored a UK-wide sample of

colonies since 1986. These data remained

unchanged from BoCC4 for most of the

breeding seabirds.

729

British Birds 114 • December 2021 • 723–747

The status of our bird populations: BoCC5 and IUCN2

! Population estimates from the Avian

Population Estimates Panel (Woodward

et al. 2020a).

! GWCT’s National Gamebag Census

(Aebischer 2019).

The process adopted the voluntary appli-

cation of the National Statistics Code of

Practice (https://code.statisticsauthority.

gov.uk/voluntary-application). A statement of

compliance is shown in the SOM.

Results

BoCC5

Former breeders

The two preceding BoCC reviews (Eaton et al.

2009, 2015) presented a list of former regularly

breeding species in the UK. All eight species

identified as such in BoCC4 remain as former

breeders in BoCC5 (table 1).

In addition, Golden Oriole

Oriolus oriolus is now added

to this list, as there have been

no confirmed breeding

records since 2009. All but one

of the former breeders were

not considered further and

removed from the Red, Amber

and Green list process. Black

Te rn Chlidonias niger

remained as it was assessed for

its passage population.

Ta b l e 1 . Former regularly breeding species in the UK, with status from previous BoCC reviews.

Species are placed on the Red (

) or Amber (

) lists, or identified as a former breeder (FB).

Previous BoCC reviews Last confirmed

1 (1996) 2 (2002) 3 (2009) 4 (2015) breeding attempt

Great Bustard Otis tarda* FB FB FB FB c.1833

Kentish Plover Charadrius alexandrinus FB FB FB FB 1979

Temminck’s Stint Calidris temminckii A A R FB 1993

Black Tern Chlidonias niger FB FB FB FB 1975

Great Auk Pinguinus impennis FB FB FB FB c.1812

Snowy Owl Bubo scandiacus FB FB FB FB 1975

Wryneck Jynx torquilla R R R FB 2002

Golden Oriole Oriolus oriolus A A R R 2009

European Serin Serinus serinus A A A FB 2006

* Although a Great Bustard reintroduction project has been under way since 2004, the population is not yet considered

self-sustaining (BOU 2017) and was therefore not assessed for BoCC5.

James Kennerley

The updated Red, Amber and Green species lists

We assessed 245 species for the Red, Amber

and Green lists in BoCC5. We placed 70

(29%) species on the Red list, 103 (42%) on

the Amber list and 72 (29%) on the Green

list (table 2).

A total of 29 species (12%) have moved

lists since BoCC4: 11 species joined the Red

list, with Ptarmigan Lagopus muta and

Greenfinch Chloris chloris moving straight

from Green to Red, and Bewick’s Swan

Cygnus columbianus, Common Goldeneye

Bucephala clangula, Smew Mergellus albellus,

Common Swift Apus apus, Dunlin Calidris

alpina, Purple Sandpiper C. maritima, Leach’s

Storm-petrel, Montagu’s Harrier Circus

pygargus and House Martin Delichon urbicum

moving from Amber to Red.

462. Golden Oriole Oriolus

oriolus, Uz beki st an , A pr il 20 18 .

With the last confirmed breed-

ing in 2009, Golden Oriole

moves to the list of former

breeding species in BoCC5.

730 British Birds 114 • December 2021 • 723–747

Six species moved from Green to Amber

owing to increasing rates of decline in

breeding or non-breeding populations: Red-

breasted Merganser Mergus serrator, Moorhen

Gallinula chloropus, Eurasian Sparrowhawk

Accipiter nisus, Sedge Warbler Acrocephalus

schoenobaenus, Common Whitethroat

Curruca communis and Northern Wheatear

Oenanthe oenanthe. A further three species

moved from Green to Amber owing to other

criteria: Rook Corvus frugilegus is now classed

Stanbury et al.

as Vulnerable at a European scale; and, in

recognition of the significance of the UK

population in a European context (now >20%

of the breeding population), Wood Pigeon

Columba palumbus and Wren Troglodytes

troglodytes also move up to Amber.

The status of nine species has improved.

Five species moved from Red to Amber owing

to less severe declines: Song Thrush Turdus

philomelos, Redwing T. iliacus, Pied Flycatcher

Ficedula hypoleuca, Black Redstart Phoenicurus

Ptarmigan

In Britain, the Ptarmigan is restricted to the arctic-alpine heaths of the Scottish

Highlands, with a population estimated at 2,000–15,000 pairs. The wide range in the estimate

reflects cyclical fluctuations and a lack of formal surveys. As a quarry species, it may be hunted

between 12th August and 10th December. The numbers shot and reported by Highland estates to

GWCT’s National Gamebag Census represent the only source of continuous long-term data on

Ptarmigan in Scotland. Analysed in a similar way to standard avian monitoring data (Aebischer

2019), shooting returns (‘bags’) can be converted into annual indices to reveal the trend over

time from 1961 to 2019 (fig. 1). The indices fluctuate considerably from year to year but show an

overall decline from start to end (58 years) of 81% (95% confidence limits 39–94% decline).

Interpreting trends in bag data is complicated because they reflect the effects of both abundance

and shooting effort. Bags have, however, been found to be a good surrogate for abundance of

Red Grouse Lagopus lagopus (Cattadori et al. 2003) and have been used to infer population fluc-

tuations in Ptarmigan elsewhere (Nielsen & Pétursson 1995). The decline is consistent with the

likely sensitivity of Ptarmigan to a northwards and upwards contraction of montane habitat

caused by climate change (Moss 1998); the species has already been lost from lower marginal

areas, especially in the southwest (Balmer et al. 2013), and 75% of estates reported declines

across its southern range (Fletcher et al. 2013). Dedicated surveys of abundance, distribution and

habitat are urgently needed to corroborate the trends in bags and monitor future change.

BOX 1

Fig. 1. Annual bag index (± 95% confidence limits) for Ptarmigan Lagopus muta in Scotland,

1961–2019, from GWCT’s National Gamebag Census.

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

bag index (1961=1)

1960 1970 1980 1990 2000 2010 2020

year

731

British Birds 114 • December 2021 • 723–747

The status of our bird populations: BoCC5 and IUCN2

ochruros and Grey Wagtail

Motacilla cinerea. White-

tailed Eagle Haliaeetus

albicilla moved from Red

to Amber as it no longer

qualifies for Historical Decline (now HD

recovering; see also box 5). Red Grouse

Lagopus lagopus, Mute Swan Cygnus olor and

Common Kingfisher Alcedo atthis moved

from the Amber to the Green list.

Native partridges and grouse had the

highest proportion of Red-listed species in

BoCC5 (fig. 2), followed by: buntings;

thrushes; swallows, martins and swifts;

finches; waders; chats and flycatchers; and

wildfowl. No herons and spoonbills or crows

and jays were Red-listed. Further details of

the BoCC assessments, along with race-level

results, can be found in the SOM.

IUCN2 overview

The second IUCN Regional Red List review

of extinction risk for Great Britain assessed

243 species, making 293 individual assess-

ments (210 breeding, 83 non-breeding). Fifty

species were assessed for both breeding and

non-breeding populations. One species

(Great Auk Pinguinus impennis) qualified as

Extinct and seven as Regionally Extinct (all

the former breeding species shown in table 1,

with the exception of Snowy Owl, which was

not evaluated as the species had never bred

for ten consecutive years and therefore never

qualified as a colonising species under the

IUCN guidelines (IUCN 2012)). Golden

Oriole was assessed as Regionally Extinct,

having been classed as Critically Endangered

(Possibly Extinct) in the previous review

(Stanbury et al. 2017).

The final assessments for the 235 regularly

occurring, or extant, species is presented in

table 2. Of these 235 species, 108 (46%) had at

least one population (breeding and/or non-

breeding) that qualified as threatened with

extinction (21 Critically Endangered, 41

Endangered, 46 Vulnerable).

Of the 285 separate assessments of breeding

and non-breeding populations, 21 qualified as

Critically Endangered, 43 as Endangered, 58 as

Vu ln er ab le , 3 3 a s N ea r T hr ea te ne d, 127 a s o f

Least Concern and three as Data Deficient.

Hence, an estimated 43% of currently occur-

ring populations qualified as threatened with

extinction. The corresponding figure was

greater for non-breeding assessments (50%)

than breeding assessments (41%).

The recent reassessment of generation

lengths by BirdLife International (Bird et al.

2020) resulted in the time window examined

for the assessments changing for 225 of the

243 species when compared with those used

for IUCN1. On this basis, coupled with it

being only four years since Stanbury et al.

(2017), we do not present a detailed assess-

ment of change. However, there were some

notable differences between the assessments.

Both Spotted Crake Porzana porzana and

Leach’s Storm-petrel move to Critically

Endangered, from Endangered and Least

Concern respectively. Ten other populations,

all previously assessed as Near Threatened or

of Least Concern, move to a higher threat

status by at least two categories. Breeding

Fig. 2. Proportion of

species allocated to the Red,

Amber and Green lists in

BoCC5, overall and split into

different groupings. Group-

ings largely based around

HBW & BirdLife Inter-

national (2020) families.

n= number of species.

* Breeding seabird

assessments were the

same as in BoCC4.

All species (n=245)

Partridges & Grouse (n=6)

Buntings & Longspurs (n=6)

Thrushes (n=6)

Swallows, Martins & Swifts (n=4)

Finches (n=13)

Wad ers (n= 32)

Chats & Old World Flycatchers (n=9)

Ducks, Geese & Swans (n=28)

Larks, Wagtails & Pipits (n=10)

Other Passerines (n=21)

War bler s ( n=15)

Grebes & Divers (n=8)

Seabirds (n=37)*

Pigeons & Doves (n=5)

Rails, Gallinules & Coots (n=5)

Eagles, Hawks & Falcons (n=15)

Herons & Spoonbills (n=7)

Crows & Jays (n=7)

0% 20% 40% 60% 80% 100%

3 4 3

6 4 11

4 5 6

2 3 3

8 21 8

1 2 2

3 6 6

5 2

1 6

9 16 3

3 4 2

11 17 4

5 3 5

2 2

3 2 1

3 3

4 1 1

70 103 72

732 British Birds 114 • December 2021 • 723–747

Stanbury et al.

Table 2. Species assessments from the UK BoCC5aand IUCN2b, with qualifying criteria. Species order follows HBW & BirdLife International (2020)e. In BoCC,

species were placed on the Red (R), Amber (A) or Green (G) lists. Previous versions shown for context (n = not assessed). IUCN threat status categories:

Critically Endangered (CR), Endangered (EN), Vulnerable (VU), Near Threatened (NT), Least Concern (LC), Data Deficient (DD) and Not Evaluated (NE).

Common Quail Coturnix coturnix R R A A Amber HDrec, BDMp1/2 EN EN C1+2a(ii) (br)

Grey Partridge Perdix perdix R R R R Red BDp1/2; BDMr2 VU VU A2b+3b+4b (br)

Red Grouse Lagopus lagopus G A A A Green LC LC (br)

Ptarmigan Lagopus muta G G G G Red BDp1/2 VU VU C1+2a(ii) (br)

Capercaillie Tetrao urogallus R R R R Red BDp2, BDr2, WDr1; BDMp1 EN EN C1 (br)

Black Grouse Lyrurus tetrix R R R R Red HD, BDp2; BDMp1, BDMr2

VU VU C1 (br)

Mute Swan Cygnus olor G A G A Green LC LC (br); LC (n-br)

Whooper Swan Cygnus cygnus A A A A Amber BR, WL EN ENoD (br); LC (n-br)

Bewick’s Swan Cygnus columbianus A A A A Red WDp1; ERLOB, WDMp2, WL, WI CR CR A2b+3b+4b (n-br)

Brent Goose Branta bernicla A A A A Amber WL, WI LC LC (n-br)

Barnacle Goose Branta leucopsis A A A A Amber WL LC LC (n-br)

Greylag Goose Anser anser A A A A Amber WL, WI LC LC (br); LC (n-br)

‘Bean Goose’ Anser fabalisc A A A A Amber WDMp1, WR EN EN A4b+C1 (n-br)

Pink-footed Goose Anser brachyrhynchus A A A A Amber WL, WI LC LC (n-br)

White-fronted Goose Anser albifrons A A G R Red WDp1/2 EN EN A2b+3b+4b (n-br)

Long-tailed Duck Clangula hyemalis G A G R Red IUCN NT NT C1+2a(ii) (n-br)

Common Eider Somateria mollissima A A A A Amber ERLOB, WDMp1/2 EN EN A4b (n-br)

Ve l v e t S c o t e r Melanitta fusca A A A R Red IUCN; ERLOB, WL VU VU C1+2a(ii) (n-br)

Common Scoter Melanitta nigra R R R R Red BDp2, BDr1/2; BDMp1, BR, WL CR CR C2a(ii) (br); LC (n-br)

Common Goldeneye Bucephala clangula A A A A Red WDp1; BR VU VU D1 (br); VU A2b+3b+4b (n-br)

Smew Mergellus albellus G G A A Red WDp1; WDMp2, WR CR CR A4b+C1+2a(ii) (n-br)

Goosander Mergus merganser G G G G Green LC LC (n-br)

Red-breasted Merganser Mergus serrator G G G G Amber WDMp1 VU NT A2c+3c+4c (br); VU A2b+3b+4b (n-br)

Common Shelduck Tadorna tadorna A A A A Amber BDMp1, WDMp1, WL EN EN A4b (br); VU A2b+3b+4b (n-br)

Common Pochard Aythya ferina A A A R Red IUCN, WDp1; ERLOB, WDMp2, BDMr1/2 EN VU A2c+3c+4c (br); EN A2b+3b+4b (n-br)

Previous BoCC

reviews

BoCC5 Red- & Amber-list IUCN2 population assessment with qualifying

Species qualifying criteriaa criteriab(br = breeding; n-br = non-breeding)

1 (1996)

2 (2002)

3 (2009)

4 (2015)

BoCC5 species

assessment

IUCN2 species

assessment

733

British Birds 114 • December 2021 • 723–747

The status of our bird populations: BoCC5 and IUCN2

Table 2. cont.

Tu ft e d Du c k Aythya fuligula G G A G Green VU VU A4b (br); LC (n-br)

Greater Scaup Aythya marila A A R R Red WDp2; WDMp1, WL EN EN A2b+3b+4b (n-br)

Garganey Spatula querquedula A A A A Amber BR EN EN D (br)

Shoveler Spatula clypeata A A A A Amber WI LC LC (br); LC (n-br)

Gadwall Mareca strepera A A A A Amber WI LC LC (br); LC (n-br)

Eurasian Wigeon Mareca penelope A A A A Amber WL, WI VU VU D1 (br); NT A4b (n-br)

Mallard Anas platyrhynchos G G A A Amber WDMp1/2 VU LC (br); VU A4b (n-br)

Pintail Anas acuta A A A A Amber ERLOB, BDMp1, BDMr1/2, BR, WL, WI CR CR C2a(ii) (br); VU A2b+3b+4b (n-br)

Eurasian Teal Anas crecca A A A A Amber WI LC LC (br); LC (n-br)

Little Grebe Tachybaptus ruficollis G G A G Green LC LC (br); LC (n-br)

Red-necked Grebe Podiceps grisegena A A A R Red WDp1; ERLOB, WR CR CR C2a(ii) (n-br)

Great Crested Grebe Podiceps cristatus G G G G Green LC LC (br); LC (n-br)

Slavonian Grebe Podiceps auritus A A A R Red IUCN, BDp1/2; BDMr1, BR, WI CR CR C2a(ii) (br); VU D1 (n-br)

Black-necked Grebe Podiceps nigricollis A A A A Amber ERLOB, BR, WR EN EN D (br); EN D (n-br)

Rock Dove/Feral Pigeon Columba livia G G G G Green NT NT A2b+3b+4b (br)

Stock Dove Columba oenas A A A A Amber BI LC LC (br)

Wo o d P i g e on Columba palumbus G G G G Amber BI LC LC (br)

Tu r tl e D ov e Streptopelia turtur R R R R Red IUCN, BDp1/2, BDr2; ERLOB, BDMr1

CR CR A2b+3b+4b (br)

Collared Dove Streptopelia decaocto G G G G Green NT NToA4b (br)

European Nightjar Caprimulgus europaeus R R R A Amber BDMr2 LC LC (br)

Common Swift Apus apus G G A A Red BDp1 EN EN A2b+3b+4b (br)

Common Cuckoo Cuculus canorus G A R R Red BDp2; BDMp1 LC LC (br)

Wa te r R a i l Rallus aquaticus A A G G Green LC LC (br)

Corn Crake Crex crex R R R R Red BDp2, BDr2; HDrec LC LC (br)

Spotted Crake Porzana porzana A A A A Amber BR CR CR C2a(ii) (br)

Moorhen Gallinula chloropus G G G G Amber BDMp2 VU VU A4b (br)

Common Coot Fulica atra G G G G Green VU VU A4b (br); VU A4b (n-br)

Common Crane Grus grus A A A A Amber BR, WR VU VUoD (br)

Red-throated Diver Gavia stellata A A A G Green NT NT A2c+3c+4c (br); LC (n-br)

Black-throated Diver Gavia arctica A A A A Amber BR, WR VU VU D1 (br)

Great Northern Diver Gavia immer A A A A Amber WI LC LC (n-br)

European Storm-petrel Hydrobates pelagicus* A A A A Amber BL LC LC (br)

Leach’s Storm-petrel Oceanodroma leucorhoa

A A A A Red IUCN, BDp1; BL, BI CR CR A4b (br)

Fulmar Fulmarus glacialis* G A A A Amber ERLOB, BL LC LC (br)

734 British Birds 114 • December 2021 • 723–747

Stanbury et al.

Table 2. cont.

Sooty Shearwater Ardenna grisea G G A G Green NE NE

Great Shearwater Ardenna gravis G G G G Green NE NE

Manx Shearwater Puffinus puffinus* A A A A Amber BDMr2, BL, BI LC LC (br)

Balearic Shearwater Puffinus mauretanicus n n R R Red IUCN; ERLOB, WI VU VU D1 (n-br)

Eurasian Spoonbill Platalea leucorodia n A A A Amber BR, WR VU VUoD (br); VUoD (n-br)

Eurasian Bittern Botaurus stellaris R R R A Amber HDrec, BR, WR VU VU D1 (br); NToD1 (n-br)

Little Bittern Ixobrychus minutus n n n n Amber BR CR CR D (br)

Cattle Egret Bubulcus ibis n n n n Amber BR VU VUoD (n-br)

Grey Heron Ardea cinerea G G G G Green VU VU A4b (br); LC (n-br)

Great White Egret Ardea alba n n n n Amber BR, WR EN ENoD (br); VUoD (n-br)

Little Egret Egretta garzetta n A A G Green LC LC (br); LC (n-br)

Northern Gannet Morus bassanus* A A A A Amber BL, BI LC LC (br)

Shag Phalacrocorax aristotelis

* A A A R Red BDp1; BDMp2, BI EN EN A2b+3b+4b (br)

Great Cormorant Phalacrocorax carbo* G A G G Green NT NToA4b (br); LC (n-br)

Stone-curlew Burhinus oedicnemus R R A A Amber BDMr2, BL VU VU A2c+3c+4c+D1 (br)

Oystercatcher Haematopus ostralegus A A A A Amber ERLOB, WL, WI, BI VU VU A4b (br)

Avo ce t Recurvirostra avosetta A A A A Amber BL, WL LC LC (br); LC (n-br)

Black-winged Stilt Himantopus himantopus A n n n Amber BR NE NE

Grey Plover Pluvialis squatarola A A A A Amber WDMp1, WL VU VU A2b+3b+4b (n-br)

European Golden Plover Pluvialis apricaria A G A G Green LC LC (br); LC (n-br)

Dotterel Charadrius morinellus

A A A R Red BDp1 VU VU A2b+3b+4b+C1+2a(ii)+D1 (br)

Ringed Plover Charadrius hiaticula A A A R Red WDp1; BDMp1, WDMp2, WI VU

NT A2b+3b+4b+C1+2a(ii) (br);

VU A2b+3b+4b (n-br)

Little Ringed Plover Charadrius dubius G G G G Green LC LC (br)

Northern Lapwing Vanellus vanellus A A R R Red BDp2; ERLOB, BDMp1, WDMp1 VU VU A2b+3b+4b (br); VU A2b+3b+4b (n-br)

Whimbrel Numenius phaeopus A A R R Red BDp1, BDr1; BDMr2, WR EN EN A2bc+3bc+4bc+C1+2a(ii) (br)

Eurasian Curlew Numenius arquata A A A R Red BDp2; BDMp1, WDMp1, BI EN EN A4b (br)

Bar-tailed Godwit Limosa lapponica A A A A Amber WL, WI VU VU A4b (n-br)

Black-tailed Godwit Limosa limosa R R R R Red HD; BDMr1, BR, WL EN EN C2a(i)+D (br); LC (n-br)

Tu r ns t o ne Arenaria interpres A A A A Amber WDMp1 VU VU A4b (n-br)

Red Knot Calidris canutus A A A A Amber WL, WI LC LC (n-br)

Ruff Calidris pugnax A A R R Red BDr1; BDMp1/2, BR CR CR D (br); EN A4b+C2a(ii) (n-br)

Curlew Sandpiper Calidris ferruginea G G G A Amber ERLOB NE NE

Sanderling Calidris alba G G G A Amber WL LC LC (n-br)

735

British Birds 114 • December 2021 • 723–747

The status of our bird populations: BoCC5 and IUCN2

Table 2. cont.

Dunlin Calidris alpina A A R A Red WDp2; WDMp1, BDMr1, BL, WL VU VU A2c+3c+4c (br); VU A2b+3b+4b (n-br)

Purple Sandpiper Calidris maritima A A A A Red BDp1; WDMp1, BDMr1, BR CR CR B2ab(ii,iv,v)+C2a(i,ii)+D (br);

VU A2b+3b+4b+C1+2a(ii) (n-br)

Little Stint Calidris minuta G G G G Green NE NE

Wo o dc o c k Scolopax rusticola A A A R Red BDr2; BDMr1

VU VU A2c+3c+4c (br); NT A2b+3b+4b (n-br)

Common Snipe Gallinago gallinago A A A A Amber ERLOB, WDMp1, BDMr2 VU LC (br); VU A4b (n-br)

Jack Snipe Lymnocryptes minimus A G A G Green LC LC (n-br)

Red-necked Phalarope Phalaropus lobatus R R R R Red HD; BR EN EN D (br)

Common Sandpiper Actitis hypoleucos G G A A Amber BDMp1/2, WR NT NT A2b+3b+4b (br)

Green Sandpiper Tringa ochropus G A A A Amber BDMr1, BR, WR CR CR C1+D (br); VU D1 (n-br)

Spotted Redshank Tringa erythropus G A A A Amber WR EN EN D (n-br)

Greenshank Tringa nebularia A G G A Amber BL LC LC (br)

Common Redshank Tringa totanus A A A A Amber ERLOB, BDMp1, BDMr1/2, WI VU VU A2bc+3bc+4bc (br); NT A2b+3b+4b (n-br)

Wo o d S a n d pi p e r Tringa glareola A A A A Amber BR, WR EN EN D (br)

Little Gull Hydrocoloeus minutus A G A G Green NE NE

Kittiwake Rissa tridactyla* G A A R Red BDp1/2; ERLOB CR CR A4b (br)

Black-headed Gull Chroicocephalus ridibundus

G A A A Amber WDMp1, WI VU LC (br); VU A2b+3b+4b (n-br)

Mediterranean Gull Ichthyaetus melanocephalus

A A A A Amber BL LC LC (br)

Common Gull Larus canus* A A A A Amber WI LC LC (br); LC (n-br)

Lesser Black-backed Gull Larus fuscus* A A A A Amber BL, BI DD DD (br)

Herring Gull Larus argentatus* A A R R Red BDp2, WDp1; BI, WI EN DD (br); EN A2b+3b+4b (n-br)

Ye l l o w - l e gg ed Gu l l Larus michahellis* n n A A Amber BR EN ENoD (br); LCo(n-br)

Caspian Gull Larus cachinnans n n n A Amber WR VU VUoD (n-br)

Iceland Gull Larus glaucoides G G A A Amber WR NT NToD1 (n-br)

Glaucous Gull Larus hyperboreus G G A A Amber WR VU VUoD (n-br)

Great Black-backed Gull Larus marinus* G G A A Amber BDMp2, WDMp1 EN LC (br); EN A2b+3b+4b (n-br)

Little Tern Sternula albifrons* A A A A Amber BDMr2, BL VU VU A2c+3c+4c (br)

Black Tern Chlidonias niger (passage only) G G A G Green NE

Roseate Tern Sterna dougallii* R R R R Red BDp1/2, BDr2; BDMr1, BR EN ENoA2b+C2a(ii) (br)

Common Tern Sterna hirundo* G G A A Amber BL NT NT A2b+3b+4b (br)

Arctic Tern Sterna paradisaea* A A A A Amber BDMp1, BDMr1

VU VU A2c+3c+4c (br)

Sandwich Tern Thalasseus sandvicensis* A A A A Amber BDMp1, BL LC LC (br)

Long-tailed Skua Stercorarius longicaudus G G G G Green NE NE

Arctic Skua Stercorarius parasiticus* G G R R Red BDp1; BDMp2

CR CR A4b (br)

736 British Birds 114 • December 2021 • 723–747

Stanbury et al.

Table 2. cont.

Pomarine Sku a Stercorarius pomarinus G G G G Green NE NE

Great Skua Stercorarius skua

* A A A A Amber BI, BL LC LC (br)

Puffin Fratercula arctica* A A A R Red IUCN; ERLOB, BDMr2, BL LC LC (br)

Black Guillemot Cepphus grylle

* A A A A Amber BDMr1 LC LC (br)

Razorbill Alca torda* A A A A Amber BL, BI LC LC (br)

Little Auk Alle alle G G G G Green DD DD (n-br)

Common Guillemot Uria aalge* A A A A Amber BL, BI LC LC (br)

Barn Owl Tyto alba A A A G Green LC LC (br)

Long-eared Owl Asio otus G G G G Green LC LC (br)

Short-eared Owl Asio flammeus A A A A Amber BDMr1/2 EN EN A2c+3c+4c (br)

Ta w ny O w l Strix aluco G G G A Amber BDMp1/2 NT NT A2b+3b+4b (br)

Osprey Pandion haliaetus R A A A Amber HDrec, BR NT NToD1 (br)

Honey-buzzard Pernis apivorus A A A A Amber BR EN EN D (br)

Golden Eagle Aquila chrysaetos A A A G Green NT NT D1 (br)

Marsh Harrier Circus aeruginosus R A A A Amber BL LC LCo(br)

Hen Harrier Circus cyaneus R R R R Red HD; BDMp1

EN EN C1 (br)

Montagu’s Harrier Circus pygargus A A A A Red BDp1; BDMr2, BR CR CR A4b+C1+2a(ii)+D (br)

Eurasian Sparrowhawk Accipiter nisus G G G G Amber BDMp1 VU VU A4b (br)

Northern Goshawk Accipiter gentilis G G G G Green NT NT D1 (br)

White-tailed Eagle Haliaeetus albicilla R R R R Amber HDrec, BR EN EN D (br)

Red Kite Milvus milvus R A A G Green LC LC (br)

Common Buzzard Buteo buteo G G G G Green LC LC (br)

Common Kingfisher Alcedo atthis A A A A Green VU VU C1+2a(ii) (br)

Green Woodpecker Picus viridis A A A G Green NT NT A2b+3b+4b (br)

Lesser Spotted Woodpecker Dryobates minor G R R R Red BDp1/2; BDMr1/2 EN EN A2b+3b+4b+C1+2a(ii) (br)

Great Spotted Woodpecker Dendrocopos major G G G G Green LC LC (br)

Common Kestrel Falco tinnunculus A A A A Amber BDMp1/2 VU VU A4b (br)

Merlin Falco columbarius R A A R Red HD; ERLOB EN EN C2a(ii) (br)

Hobby Falco subbuteo G G G G Green NT NT A4b (br)

Pere grin e Falcon Falco peregrinus A A G G Green LC LC (br)

Red-backed Shrike Lanius collurio R R R R Red HD, BDp1/2, BDr2; BR CR CR D (br)

Red-billed Chough Pyrrhocorax pyrrhocorax A A A G Green VU VU D1 (br)

Eurasian Jay Garrulus glandarius G G G G Green LC LC (br)

Magpie Pica pica G G G G Green LC LC (br)

737

British Birds 114 • December 2021 • 723–747

The status of our bird populations: BoCC5 and IUCN2

Table 2. cont.

Jackdaw Coloeus monedula

G G G G Green LC LC (br)

Rook Corvus frugilegus G G G G Amber ERLOB NT NT A2b+3b+4b (br)

Common Raven Corvus corax G G G G Green LC LC (br)

‘Carrion/Hooded Crow’ Corvus coronec,d G G G G Green LC LC (br)

Coal Tit Periparus ater G G G G Green LC LC (br)

Crested Tit Lophophanes cristatus A G A G Green LC LC (br)

Marsh Tit Poecile palustris A R R R Red BDp2; BDMp1 NT NT A2b+3b+4b (br)

Will ow Tit Poecile montanus A R R R Red BDp1/2, BDr2; BDMr1, WDMr1 EN EN A2c+3c+4c (br)

Blue Tit Cyanistes caeruleus G G G G Green LC LC (br)

Great Tit Parus major G G G G Green LC LC (br)

Shore Lark Eremophila alpestris n n A A Amber WR EN EN D (n-br)

Wo o dl a r k Lullula arborea R R A G Green LC LC (br)

Skylark Alauda arvensis R R R R Red BDp2

LC LC (br); LC (n-br)

Bearded Tit Panurus biarmicus A A A G Green LC LC (br)

Sedge Warbler Acrocephalus schoenobaenus G G G G Amber BDMp2 NT NT A4b (br)

Marsh Warbler Acrocephalus palustris R R R R Red BDp1/2; BR CR D (br)

Reed Warbler Acrocephalus scirpaceus G G G G Green LC LC (br)

Savi’s Warbler Locustella luscinioides A R R R Red BDp1/2; BDMr1, BR CR CR D (br)

Grasshopper Warbler Locustella naevia A R R R Red BDp2 LC LC (br)

House Martin Delichon urbicum G A A A Red BDp2 NT NT A2b+3b+4b (br)

Barn Swallow Hirundo rustica A A A G Green VU VU A2b+3b+4b (br)

Sand Martin Riparia riparia A A A G Green LC LC (br)

Wo o d Wa r b l er Phylloscopus sibilatrix G A R R Red BDp1; BDMr1/2 VU VU A2c+3c+4bc (br)

Ye l l o w - b r o w e d W a r b l e r Phylloscopus inornatus n n n n Amber WR EN ENoD (n-br)

Will ow Warbler Phylloscopus trochilus G A A A Amber BDMp2 LC LC (br)

Common Chiffchaff Phylloscopus collybita G G G G Green LC LC (br)

Cetti’s Warbler Cettia cetti A G G G Green LC LC (br)

Long-tailed Tit Aegithalos caudatus G G G G Green LC LC (br)

Blackcap Sylvia atricapilla G G G G Green LC LC (br)

Garden Warbler Sylvia borin G G G G Green LC LC (br)

Lesser Whitethroat Curruca curruca

G G G G Green LC LC (br)

Common Whitethroat Curruca communis

G G A G Amber BDMp2 LC LC (br)

Dartford Warbler Curruca undata

R A A A Amber HDrec, BL LC LC (br)

Short-toed Treecreeper Certhia brachydactyla G G A A Amber BR NE NE

738 British Birds 114 • December 2021 • 723–747

Stanbury et al.

Table 2. cont.

Eurasian Treecreeper Certhia familiaris G G G G Green LC LC (br)

Eurasian Nuthatch Sitta europaea G G G G Green LC LC (br)

Wre n Troglodytes troglodytes G G G G Amber BI LC LC (br)

Dipper Cinclus cinclus G G G A Amber BDMp2 LC LC (br)

Common Starling Sturnus vulgaris A R R R Red BDp1/2 VU VU A2b+3b+4b (br); LC (n-br)

Mistle Thrush Turdus viscivorus G A A R Red BDp2; BDMp1 NT NT A2b+3b+4b (br)

Song Thrush Turdus philomelos R R R R Amber BDMp2 LC LC (br)

Redwing Turdus iliacus A A R R Amber BDMr1/2, BR CR CR D (br); LC (n-br)

Blackbird Turdus merula A G G G Green LC LC (br)

Fieldfare Turdus pilaris A A R R Red BDp1/2, BDr1; BDMr2, BR CR CR A2c+3c+4c+C2a(i,ii)+D (br); LC (n-br)

Ring Ouzel Turdus torquatus A R R R Red BDp2; BDMr2

NT NT A2c+3c+4c (br)

Spotted Flycatcher Muscicapa striata R R R R Red BDp1/2 NT NT A4b (br)

Robin Erithacus rubecula G G G G Green LC LC (br)

Common Nightingale Luscinia megarhynchos A A A R Red BDp1/2; BDMr2 VU VU A4b (br)

Pied Flycatcher Ficedula hypoleuca G G A R Amber BDMp1, BDMr1 NT NT A2c+3c+4c (br)

Black Redstart Phoenicurus ochruros A A A R Amber BR, WR VU VUoD (br); NToD1 (n-br)

Common Redstart Phoenicurus phoenicurus A A A A Amber BDMr2 LC LC (br)

Whinchat Saxicola rubetra G G A R Red BDp1; BDMr1/2 NT NT A2c+3c+4bc (br)

European Stonechat Saxicola rubicola A A G G Green LC LC (br)

Northern Wheatear Oenanthe oenanthe G G A G Amber BDMp1 EN EN A4b (br)

Goldcrest Regulus regulus G A G G Green LC LC (br)

Firecrest Regulus ignicapilla A A A G Green LC LC (br)

Wa xw i n g Bombycilla garrulus G G G G Green LC LC (n-br)

Dunnock Prunella modularis A A A A Amber BDMp2 LC LC (br)

House Sparrow Passer domesticus G R R R Red BDp2

LC LC (br)

Tr ee S p a r r ow Passer montanus R R R R Red BDp2; BDMr2

VU VU A2c+3c+4c (br)

Tr ee P i p i t Anthus trivialis G A R R Red BDp2; BDMr2 LC LC (br)

Meadow Pipit Anthus pratensis G A A A Amber BDMp2 LC LC (br)

Wa te r P i p it Anthus spinoletta G G A A Amber WR EN EN D (n-br)

Rock Pipit Anthus petrosus G G G G Green LC LC (br)

Ye l l o w Wa gt a il Motacilla flava G A R R Red BDp2; BDMp1, BDMr1/2 NT NT A2c+3c+4c (br)

Grey Wagtail Motacilla cinerea G A A R Amber BDMp2 NT NT A2b+3b+4b (br)

White/Pied Wagtail Motacilla alba G G G G Green LC LC (br)

Common Chaffinch Fringilla coelebs G G G G Green EN EN A4b (br)

739

British Birds 114 • December 2021 • 723–747

The status of our bird populations: BoCC5 and IUCN2

Table 2. cont.

Brambling Fringilla montifringilla A G G G Green LC LC (n-br)

Hawfinch Coccothraustes coccothraustes A A R R Red BDp1, BDr1/2 EN EN A2bc+3bc+4bc+C1+2a(ii) (br)

Bullfinch Pyrrhula pyrrhula R R A A Amber BDMp2 LC LC (br)

Greenfinch Chloris chloris G G G G Red BDp1/2 EN EN A2b+3b+4b (br)

Tw i t e Linaria flavirostris R R R R Red HD, BDp1 EN EN A2b+3b+4b (br)

Linnet Linaria cannabina R R R R Red BDp2

LC LC (br)

‘Redpoll’ Acanthis flammeac,d G A R R Red BDp2

LC LC (br)

Parrot Crossbill Loxia pytyopsittacus A A A A Amber BR EN EN D (br)

Scottish Crossbill Loxia scotica R R A A Amber BI LC LC (br)

Common Crossbill Loxia curvirostra G G G G Green LC LC (br)

Goldfinch Carduelis carduelis A G G G Green LC LC (br)

Siskin Spinus spinus G G G G Green LC LC (br)

Lapland Bunting Calcarius lapponicus G G A A Amber WR VU VU D1 (n-br)

Snow Bunting Plectrophenax nivalis A A A A Amber BR EN EN D (br); LC (n-br)

Corn Bunting Emberiza calandra R R R R Red HD, BDp2, BDr2; BDMp1, BDMr1, WDMr1

NT NT A2c+3c+4c (br)

Cirl Bunting Emberiza cirlus R R R R Red BDr2 LC LC (br)

Ye l l o w h a mm e r Emberiza citrinella G R R R Red BDp2; BDMp1 LC LC (br)

Reed Bunting Emberiza schoeniclus R R A A Amber BDMp2 LC LC (br)

a BoCC Red-list criteria IUCN: Globally threatened; HD: historical decline in the breeding population; BDp1/2: severe breeding population decline over 25 years/longer term; WDp1/2: severe

non-breeding population decline over 25 years/longer term; BDr1/2: severe breeding range decline over 25 years/longer term; WDr1: severe non-breeding range decline over 25 years. BoCC Amber-list

criteria ERLOB: Threatened in Europe; HDrec: historical decline – recovery; BDMp1/2: moderate breeding population decline over 25 years/longer term; WDMp1/2: moderate non-breeding population

decline over 25 years/longer term; BDMr1/2: moderate breeding range decline over 25 years/longer term; WDMr1: moderate non-breeding range decline over 25 years; BR/WR: breeding/non-breeding

rarity; BL/WL: breeding/non-breeding localisation; BI/WI: breeding/non-breeding international importance.

b IUCN main criteria A = population size reduction; B = restricted geographic range; C = small population size and decline; D = very small or restricted population. Details on subcriteria can be

found at www.iucnredlist.org.

denotes that the taxa was downlisted during the regional stage of the IUCN process owing to potential rescue effects.

c The assessments follow HBW & BirdLife International (2020) taxonomy. The following six taxa, recognised as species by Gill et al. (2020) but as races by HBW & BirdLife International, were assessed

at race level (with BoCC5 and IUCN2 assessments in parentheses): Taiga Bean Goose Anser f. fabalis (Red, CR); Tundra Bean Goose A. f. rossicus (Amber, VU); Carrion Crow Corvus c. corone (Green,

LC); Hooded Crow C. c. cornix (Green, EN); Common Redpoll Acanthis f. flammea (Amber, EN); Lesser Redpoll A. f. cabaret (Red, LC).

d Species-level taxonomic changes since BoCC4/IUCN1.

e Scientific names in HBW & BirdLife International (2020) differ from those used here. The HBW & BirdLife International scientific names are as follows: Leach’s Storm-petrel Hydrobates leucorhous;

Shag Gulosus aristotelis; Dotterel Eudromias morinellus; Black-headed Gull Larus ridibundus; Mediterranean Gull L. melanocephalus; Great Skua Catharacta skua; Jackdaw Corvus monedula; Lesser

Whitethroat Sylvia curruca; Common Whitethroat S. communis; Dartford Warbler S. undata.

* Seabird assessments based on those from Eaton et al. (2015) and Stanbury et al. (2017).

740 British Birds 114 • December 2021 • 723–747

Common Quail

Coturnix coturnix, Northern

Wheatear, Common Chaffinch Fringilla

coelebs and Twite Linaria flavirostris move to

Endangered, while breeding Ptarmigan,

Tu ft e d D uc k Aythya fuligula, Oystercatcher

Haematopus ostralegus, Common Kingfisher,

Barn Swallow Hirundo rustica and non-

breeding Bar-tailed Godwit Limosa lapponica

move to Vulnerable. Conversely, breeding

populations of Great Crested Grebe Podiceps

cristatus, Woodlark Lullula arborea and

Dartford Warbler Curruca undata move from

Vulnerable in IUCN1 to being of Least

Concern. Further details of the IUCN assess-

ments, along with race-level results, can be

found in the SOM.

Discussion

The continued long-term decline

in the status of UK bird populations

All previous BoCC assessments have high-

lighted a continuing decline in the status of

UK bird populations, with an ever-growing

Red list. Unfortunately, this trend continues

with the results from BoCC5. We have now

placed 70 species (28.6% of those assessed)

on the Red list, and the length of the Red list

has grown by three species since BoCC4, with

11 species moving on and six moving off to

Amber. Two other species were not assessed

Stanbury et al.

for the Red, Amber and Green lists in BoCC5:

Golden Oriole, a species that never had more

than a toehold in the UK, has now been lost

as a regular breeding species and joins the list

of former breeders, while Aquatic Warbler

(Red-listed in BoCC1 to BoCC4) was

removed in BoCC5 owing to change in

species selection criteria. Newly Red-listed

species include some of our more familiar

birds, such as Common Swift, House Martin

and Greenfinch. Two rare breeders,

Montagu’s Harrier and Purple Sandpiper, are

close to being lost from the UK, with just two

and one breeding pair, respectively, reported

in 2019 (Eaton et al. 2021). The length of the

Amber list has also grown, by seven species.

It is important to note that there were no

changes in assessment criteria between

BoCC4 and BoCC5, and any movements

between lists were as a direct result of

changes in species status.

BoCC4 saw the addition of 20 species to

the Red list with only three species moving

off to Amber. The magnitude of the changes

reported here in BoCC5 is less, but overall

more species still qualified for the Red list

than ever before (fig. 3). Since BoCC1 (25

years ago), and notwithstanding some minor

changes to taxonomy and the details of some

of our criteria, the number of former

The declining status of swifts and hirundines

Many of our aerial insectivores are in trouble. Both Common Swift and House

Martin move from the Amber to Red list in BoCC5 owing to severe population declines of 58%

(1995 to 2018) and 57% (1969 to 2018) respectively. The former is IUCN Endangered, the

latter Near Threatened. The causes of Common Swift decline are unclear and more robust evi-

dence is needed, but the loss of traditional nest sites is likely to be a contributory factor.

Conservation action has so far focused on protecting existing sites and providing artificial nest

sites, by erecting nestboxes and promoting the installation of Swift bricks within new housing

developments. Similarly, House Martins prefer to use existing nests remaining from the pre-

vious year, and house owners are encouraged to leave them in place. The causes of the House

Martin decline also remain unclear, but several factors on their breeding grounds and in Africa

have been suggested, including climate and land-use changes (Woodward et al. 2020b; Kettel et

al. 2021). Another aerial insectivore to show recent declines is the Barn Swallow, with a 31%

decrease between 2008 and 2018 (Harris et al. 2020). Although it does not currently exceed a

BoCC threshold over either assessment period, the recent decline led to Barn Swallow being

classified as Vulnerable to extinction within the IUCN2 assessment. All three species spend the

non-breeding season in the sub-Saharan humid and southern zones (Vickery et al. 2014). This

is in contrast to Sand Martin Riparia riparia, which is currently Green-listed, winters farther

north in the arid zone, and shows a 28% increase over the last 25 years (Harris et al. 2020).

BOX 2

741

British Birds 114 • December 2021 • 723–747

The status of our bird populations: BoCC5 and IUCN2

breeders has increased by four and the

number of Red-listed species has nearly

doubled (36 to 70), while the number of

species on the Green list has decreased by

almost a third, from 102 to 72.

Criteria affecting the length of the lists

Much of the increase in the length of the Red

and Amber lists arises because more species

qualify by virtue of more severe declines in

their breeding population. In BoCC5, 77

species showed breeding-abundance declines

that exceeded at least the Amber-list

threshold (54 for 25-year decline and 57 for

longer-term decline), up from 29 in BoCC1

(25-year decline only).

No species qualified for the Red or Amber

list through non-breeding population

declines in BoCC1 but 23 species, primarily

wildfowl and waders, exceeded at least the

Amber list threshold in this review. The pub-

lication of the most recent atlas (Balmer et

al. 2013) saw the number of species quali-

fying for the breeding range criteria

(BDr1/2/BDMr1/2) more than double, from 21

in BoCC1 to 46 in BoCC4 (these data

remained unchanged in BoCC5). The

number of species qualifying for the

Historical Decline (HD), localisation

(BL/WL) and international importance

(BI/WI) criteria shows a small reduction

over time, with eight, 38 and 34 species qual-

ifying in BoCC5, respectively.

There has been a worrying trend towards

more of the UK’s regularly occurring species

being classed as threatened with global extinc-

tion by the IUCN (www.iucnredlist.org); with

the addition of Leach’s Storm-petrel and

Kittiwake Rissa tridactyla,there are now nine.

Existing and emerging themes

Previous BoCC reviews have highlighted the

plight of bird communities breeding in farm-

land, the uplands and woodland. In BoCC5, we

found no improvement in the overall status of

the first two of these groupings (as defined by

Gibbons et al. 1993 and Eaton et al. 2015);

indeed, more species have been Red-listed.

Since BoCC4, the number of Red-listed farm-

land species increased from 12 to 14, with the

addition of Montagu’s Harrier and Greenfinch,

while Common Whitethroat moved from

Green to Amber. It is a similar story among

species associated with uplands, where the

number of Red-listed species increased from

12 to 14, with the addition of Ptarmigan (see

also box 1), Purple Sandpiper and Dunlin,

while Grey Wagtail showed a positive move

back to Amber. Furthermore, Northern

Wheatear and Red-breasted Merganser moved

from Green to Amber. Note, however, that

both Dunlin and Red-breasted Merganser

moved lists owing to declines in non-breeding

population; we do not have robust breeding

Fig. 3. Length of the Red,

Amber and Green lists

across all five BoCC reviews.

Note that the assessment

process has developed over

time and this figure does

not take account of changes

to criteria, taxonomy or

species joining or being

omitted. Some changes in

Red-, Amber- and Green-list

lengths have been as a con-

sequence of these changes.

For example, the move from

using the Species of

European Conservation

Concern (SPEC) assess-

ments to the European Red

List of Birds to determine

the wider regional concern

for a species in BoCC4

resulted in a reduction in

the length of the Amber list.

250

200

150

100

number of species

Green list Amber list Red list former breeder

BoCC1 BoCC2 BoCC3 BoCC4 BoCC5

(1996) (2002) (2009) (2015) (2021)

102

110

121

126

103

742 British Birds 114 • December 2021 • 723–747

Stanbury et al.

Afro-Palearctic long-distance migrants

The populations of many species of long-distance, European-breeding Afro-

Palearctic migrants are in sharp decline. Potential causes are diverse and occur across widely

separated breeding, migration and wintering sites. Degradation of breeding habitat as well as

the interactions between habitat degradation and climatic factors in their non-breeding areas,

such as Sahel zone droughts, are believed to be key factors (Vickery et al. 2014).

The worrying plight of our Afro-Palearctic migrants in the UK was raised in BoCC3 when

Common Cuckoo, Whimbrel Numenius phaeopus, Golden Oriole, Wood Warbler Phylloscopus sibi-

latrix and Tree Pipit Anthus trivialis were all added to the Red list. These were joined by Common

Nightingale Luscinia megarhynchos, Pied Flycatcher and Whinchat Saxicola rubetra in BoCC4. The

status of these long-distance migrants continues to decline, with Common Swift and House Martin

moving to the Red list, and Sedge Warbler, Common Whitethroat and Northern Wheatear going

from the Green to Amber list in this review. Hewson & Noble (2009) were the first to note differing

trends between those that spend the non-breeding season in the arid northern zone and those that

spend it in the humid southern areas. Although the status of the arid-zone species continues to

decline (fig. 4a), it is the species that winter farther south that are of higher conservation concern

(fig. 4b). Only Pied Flycatcher shows a positive move from the Red list back to Amber, but the

trend for this species remains close to the Red-list threshold. Wryneck Jynx torquilla and Golden

Oriole joined the list of former breeders in BoCC4 and BoCC5 respectively.

BOX 3

463. Greenfinch Chloris

chloris, N or fo lk, N ov em be r

2008. In BoCC5, the

Greenfinch has moved

directly from the Green

to the Red list due to a

dramatic population crash

caused by a severe outbreak

of trichomonosis. As of

2019, the decline shows

no sign of abating.

David Tipling

Fig. 4. The changing status between BoCC1 and BoCC5 of long-distance Afro-Palearctic migrants

that spend the non-breeding season in the (a) arid zone (11 species) and (b) humid and southern

zone (18 species). Species groups and wintering zones defined by Vickery et al. (2014).

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

BoCC1 BoCC2 BoCC3 BoCC4 BoCC5

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

BoCC1 BoCC2 BoCC3 BoCC4 BoCC5

Green Amber Red former breeder

a. b.

743

British Birds 114 • December 2021 • 723–747

The status of our bird populations: BoCC5 and IUCN2

trends for either species.

It is a mixed picture in woodlands. Three

species – Pied Flycatcher, Song Thrush and

Redwing – moved off the Red list to Amber;

but we have lost Golden Oriole as a regular

breeder and Eurasian Sparrowhawk moved

from Green to Amber. It is also worth noting

that some of the movements between lists doc-

umented in this review have been due to small

variations in trend, rather than species showing

dramatic changes in fortune. For example,

Song Thrush and Pied Flycatcher, which moved

from Red to Amber owing to trends of -49.9%

and -43.4% respectively, remain (very) close to

the -50% Red-list threshold.

The plight of Afro-Palearctic migrants was

first highlighted in BoCC3, with further

declines noted in BoCC4 (see also box 3; fig.

4). The BoCC5 review has identified con-

tinued declines in the status of this group,

with two migrant aerial insectivores joining

the Red list – Common Swift and House

Martin – and others moving up to the Amber

list (see also box 2). BoCC4 highlighted

declines in several wintering wildfowl and

wader species and BoCC5 gives us little cause

for new optimism (see also box 4; fig. 5).

We n ee d to wa it f or re s ul t s o f t he c u rr e nt

census to robustly assess the status of our seabird

populations; however, Leach’s Storm-petrel

moved from Amber to Red based on the change

in its global status – now globally Vulnerable –

and the dramatic declines noted by recent

surveys on St Kilda (

Deakin et al. in press

It is important to recognise and celebrate

the few positive stories to come out of BoCC5.

Following extensive conservation action,

White-tailed Eagle has now moved from Red

Wintering waterbirds in decline

In this BoCC review, we highlight the declining status of non-breeding waterbird

populations. The UK holds internationally important assemblages of wintering wildfowl and

waders, as demonstrated by 20 species meeting our Amber-list non-breeding international

importance criterion. No wintering trends exceeded Red-list thresholds in BoCC1 and BoCC2

(fig. 5), but this has changed. BoCC3 and BoCC4 highlighted the plight of White-fronted

Goose Anser albifrons, Greater Scaup Aythya marila, Common Pochard A. ferina and Ringed

Plover Charadrius hiaticula. A further four species have now joined the Red list owing to

declines in non-breeding populations: Bewick’s Swan, Common Goldeneye, Dunlin and Smew,

while Red-breasted Merganser moved from Green to Amber. Pressures are wide-ranging, from

threats on migration, illegal hunting, ingestion of lead ammunition to the impacts of climate

change. Assessing drivers is further complicated by the fact that many wintering waterbird

populations in the UK have been affected by ‘short-stopping’, whereby species have shifted

their wintering grounds northeastwards in response to increased temperatures.

BOX 4

Fig. 5. The changing status of the

41 species within the UK wintering

waterbird indicator (JNCC 2020).

Number of species qualifying for the

Red, Amber and Green list for either

international status (IUCN, ERLOB)

or criteria relating to non-breeding

populations in the UK (WDP, WDMP,

WDR, WDMR, WR, WL, WI). Within

the IUCN assessment, 49% of these

waterbird populations were classed

as threatened. Note, Smew joined

the Red list in BoCC5 but is not

included within the indicator.

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

Green Amber Red

BoCC1 BoCC2 BoCC3 BoCC4 BoCC5

proportion of species

744 British Birds 114 • December 2021 • 723–747

to Amber, as the species no longer qualifies for

the Historical Decline criterion. In addition,

the ongoing increase in the Marsh Harrier

Circus aeruginosus population means that this

species is now considered to have fully recov-

ered from its historical decline, although it still

qualifies for the Amber list through being a

localised breeder. Other species that have

increased sufficiently to move off the Red list

are two rare breeders, Black Redstart and

Redwing. These changes are as a direct conse-

quence of recent population increases.

The UK has seen continued colonisation,

particularly by waterbirds, and we added five

new species to this review: breeding Great

White Egret, Cattle Egret, Little Bittern and

Black-winged Stilt, and non-breeding Yellow-

browed Warbler. While we welcome these

additions to our avifauna, we should simulta-

neously recognise that the arrival of new

species here owes much to man-induced

climate change, which may have an adverse

effect elsewhere in their ranges.

The updated assessment of

extinction risk in Great Britain

The benefit of undertaking the internationally

recognised standardised IUCN Regional Red

List process, in addition to BoCC, is that we

can compare the status of our bird popula-

tions with other geographical areas as well as

with other taxonomic groups in Great Britain,

plus it allows birds to be incorporated into

multi-taxa assessments and higher-level bio-

diversity indicators. IUCN2 found that 46%

Stanbury et al.

of regularly occurring species and 43% of

populations were assessed as being threatened

with extinction from Great Britain. This is

high compared with the equivalent figure for

birds in Europe (13%, BirdLife International

2021) and most other taxonomic groups in

Great Britain. The State of Nature report

(Hayhow et al. 2019) showed that 15% of

8,431 species across 11 taxonomic groups in

Great Britain were classified as threatened.

Other groups showing relatively high propor-

tions of threatened species are terrestrial

mammals (26%, Mathews & Harrower 2020),

vascular plants (22%, Cheffings & Farrell

2005) and butterflies (33%, Fox et al. 2010).

As noted by Stanbury et al. (2017), we

believe there are good reasons why the propor-

tion of threatened populations in birds in

Great Britain is high. First, the risk of extinc-

tion tends to increase as the geographical area

considered becomes smaller. Secondly, there

are fundamental biological differences between

taxonomic groups which have relevance to the

IUCN criteria. Even scarce invertebrates or

plants can still have populations in the thou-

sands of individuals, and thus do not approach

the IUCN’s qualifying thresholds for small

population size. Thirdly, data availability for

birds far exceeds that of many other taxonomic

groups thanks to the effort of volunteers, so

species can be tested robustly against more cri-

teria. We believe that, if similar data were avail-

able for other, similar-sized areas and for other

taxonomic groups, levels of assessed extinction

risk would be considerably higher than is esti-

White-tailed Eagle reintroduction

White-tailed Eagle moves from the Red to Amber list in BoCC5, as the species no

longer qualifies for the Historical Decline criterion and is now classed as HD recovering. Its

population remains small, however, and it is considered to be IUCN Endangered. The species’

reintroduction into Scotland is a conservation success story. After the failure of two early

attempts in 1959 and 1968, the release of 82 birds on Rum between 1975 and 1985, 58 birds in

northwest Scotland between 1993 and 1998 and 86 birds in east Scotland from 2007 to 2012

brought a change in fortune, with successful breeding in Scotland recommencing in 1985. By

2002, a total of 25 territories were known, increasing to 52 in 2010, 100 in 2015, and 123 in

2019. The White-tailed Eagle’s range has also expanded to the extent that birds are now

breeding as far north as Orkney, south to southern Argyll and eastwards into much of eastern

Scotland north of the Central Belt. The population has now reached a level at which moni-

toring is becoming increasingly challenging, and it is estimated that about ten new territories

are being established annually, though this may be an under-estimate. A reintroduction project

has now started in England in the Isle of Wight.

BOX 5

745

British Birds 114 • December 2021 • 723–747

The status of our bird populations: BoCC5 and IUCN2

mated currently. Therefore, although the

IUCN Red-listing process is scalable between

regions and taxa, it is not perfect, and, on this

basis, it is fair to assume there are limits to our

ability to make comparisons.

There is much commonality between the

results of IUCN2 and BoCC5 (table 3). Of the

108 species to have a population qualifying as

threatened (CR, EN, VU) through the IUCN

process, all but seven are on the BoCC Red or

Amber lists (50 on the Red list, 51 on the Amber

list). Since the IUCN Regional Red List process

focuses on extinction risk, assessments tend to

identify species with extremely low numbers,

restricted ranges and/or rapid recent declines;

justifiably so, since these are the species most

likely to become extinct. Similar criteria exist in

the BoCC process, albeit with different thresh-

olds and over different time periods. Of the

seven exceptions (IUCN threatened species on

the Green list), one qualified for criterion D

(very small population size), one for criterion C

(small population and decline) and five by

virtue of criterion A4 (a projected future

decline). The last highlights an important dif-

ference between the two processes: BoCC

focuses on the current and past status, while

IUCN focuses on current and likely future

trends (for species where reliable data indicate

that a trend is likely to continue), providing an

early warning signal of trouble ahead. Both

Common Chaffinch and Barn Swallow quali-

fied under criterion A4, show recent changes in

fortune (Woodward et al. 2020b) and may be

worthy of additional conservation attention.

Unlike BoCC, the IUCN process does not

consider the international significance of our

populations or species showing severe

declines prior to the three-generation-length

assessment window; therefore, there is less

commonality between IUCN2 and BoCC5

results than the other way around. Indeed, 49

Red- and Amber-listed species are assessed as

of Least Concern. Examples of BoCC species

whose past decline is of concern, but that are

not IUCN threatened (because they are not

currently declining to the extent they are

threatened with extinction) include

Common Cuckoo Cuculus canorus, Corn

Crake Crex crex and Skylark Alauda arvensis,

while some of our internationally significant

(and hence BoCC-listed) seabird populations

are not threatened with extinction.

Data gaps

We a re e x t r em e l y f or t u n a te i n t h e U K to h a v e a

large number of dedicated volunteers con-

tributing data towards established biodiversity-

monitoring schemes, such as BBS and WeBS.

Without these data, our prioritisation and

status assessments would not be possible.

Notwithstanding the existence of these rich

datasets, gaps in our knowledge do exist. Eaton

et al. (2015) documented these in detail and

many remain relevant: for example, we lacked

robust trends for 20 breeding species including

Short-eared Owl Asio flammeus and Scottish

Crossbill Loxia scotica. The publication of

results from the current seabird census will

make a major contribution to our under-

standing of the status of this group and fill a

large knowledge gap. It is the case though that,

owing to less species/group-specific monitoring

being undertaken (because of lower invest-

ment), we are increasingly reliant on ageing

information. For example, the last national

breeding survey of European Nightjar

Caprimulgus europaeus was in 2004, of Red-

Ta b l e 3 . Matrix showing the commonalities and differences between the BoCC5 and IUCN2

results. It excludes former breeding, Regionally Extinct and Extinct species. IUCN threat status

categories: Critically Endangered (CR), Endangered (EN), Vulnerable (VU), Near Threatened

(NT), Least Concern (LC), Data Deficient (DD), Not Evaluated (NE). The highest threat status

has been used when two different seasons were assessed for the same species.

IUCN2 assessment

CR EN VU NT LC DD NE Total

Red 16 19 15 9 11 0 0 70

Amber 5 21 25 9 39 1 3 103

Green 0 1 6 8 49 1 7 72

Total 21 41 46 26 99 2 10 245

BoCC5

assessment

746 British Birds 114 • December 2021 • 723–747

throated Gavia stellata and Black-throated

Divers G. arctica in 2006, Ringed and Little

Ringed Plovers Charadrius dubius in 2007, and

Merlin Falco columbarius in 2008, while the

most recent Winter Gull Roost Survey

(WinGS) was undertaken during the winters of

2003/04 and 2005/06. We recommend that

increased resources are made available to

ensure timely monitoring of these and other

species that may otherwise not receive the con-

servation attention they deserve.

Conclusion

The BoCC and IUCN processes provide a

robust framework for targeting conservation

actions for birds. Both allow us to track the

effectiveness of our interventions for birds

and the IUCN assessments offer the prospect

of including birds in high-level, cross-taxa

Red List-type biodiversity indicators which

can help us measure overall conservation

effectiveness and thus progress towards

national and global targets to halt and

reverse biodiversity loss.

These latest reviews, BoCC5 and IUCN2,

add to the already extensive weight of evi-

dence that many of our bird populations are

in trouble. Our findings reinforce previous

reviews and are supported elsewhere. For

example, the UK Government’s own

Biodiversity Indicators show long-term

declines in farmland birds and more recent

declines in wintering waterbirds (JNCC

2020). We highlight new species that should

now be considered of high conservation

concern, such as Leach’s Storm-petrel,

Common Swift, House Martin and

Greenfinch, but we must not forget the 59

species already on the Red list. With nearly

30% of UK species now Red-listed, further

prioritisation may be necessary unless

nature conservation action becomes bolder,

takes place over a greater scale and is much

better resourced. Whilst the need for conser-

vation action is obvious if we are to address

the current biodiversity crisis, it is vital that

we continue to monitor our bird popula-

tions and to make regular, periodic updates

to our BoCC and IUCN assessments – we

recommend a continuation of the six-year

interval – so that we can measure progress

towards relevant biodiversity targets and

refresh our priorities.

Stanbury et al.

Acknowledgments

We w oul d li ke to s ay a huge tha nk y ou t o the tho u-

sands of voluntary and professional surveyors who

have collected data on our avifauna, without whom

such assessments would be impossible. Special thanks

also to the many colleagues who have helped with

access to data and provided advice during the assess-

ment process, including Ian Burfield and Anna Staneva

at BirdLife International, Teresa Frost and Dario

Massimino at the BTO, Andrew Stevenson at

NatureScot, Richard Facey at Natural Resources Wales

(NRW), Malcolm Burgess, Fiona Burns, Richard

Gregory, Ian Johnstone and Simon Wotton at the RSPB,

Dave Baines and Phil Warren at the Game & Wildlife

Conservation Trust (GWCT), and David Stroud. This

study was funded by RSPB and Natural England as par t

of the ‘Action for Birds in England’ partnership.

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Nielsen, O. K. & Petursson, G. 1995: Population fluctuations of gyrfalcon and rock ptarmigan: analysis of export figures from Iceland. - Wildl. Biol. 1: 65-71. We analysed harvest data for gyrfalcon Falco rusticolus and rock ptarmigan Lagopus mutus from Iceland with respect to regularity in fluctuations of numbers. The gyrfalcon data concerned live trapped birds exported to Denmark between 1731 and 1793, and totalled 4,848 falcons, including 4,318 grey, 156 half-white and 374 white colour morphs. According to contemporary sources grey birds were part of the local breeding population (islandus-type birds) but the other morphs represented mainly visitors from Greenland. This is also the current situation but some of the lightest Icelandic breeders could be classified as half-white. The rock ptarmigan harvest data concerned birds exported to Europe in the period 1864-1919, in total ca 3.3 million birds. The data series for white and half-white gyrfalcons were significantly correlated (r = 0.501, p < 0.001). The data series for grey and white morphs (r = -0.099, P = 0.445) and grey and the half-white morphs (r = -0.1183, P = 0.360), showed no correlation. Time series analysis showed that the white (candicans-type) morph fluctuated irregularly. The half-white morph behaved similarly but also showed some affinity with the grey morph, and could have represented a mixture of local breeders and Greenlandic winter visitors. Grey morph gyrfalcons and rock ptarmigan showed regular fluctuations in numbers with a 10-year periodicity. The reliance of Icelandic gyrfalcons on rock ptarmigan during the early part of the breeding season and in all phases of the ptarmigan cycle is well established and may offer a case for causal connections between the two cyclic populations.

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Article

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Stephen Moss

Global climate change is no longer speculation, but reality. It will have unprecedented effects on Britain's weather and climate, and on habitats, ecosystems and the flora and fauna which comprise them, including birds. As a result, during the next century there are likely to be major changes in our avifauna: range extensions and contractions, rises and declines in populations, new colonists and extinctions as British breeding birds. Global warming will also affect patterns of migration, wintering and vagrancy, with long-distance migrants particularly at risk. In order to deal with the new challenges posed by climate change, our current conservation strategy will have to shift rapidly and radically. Whole ecosystems may have to be relocated or in some cases created from scratch, in order to deal with loss of habitat and changes in range. Whether or not this willultimately prove successful it is still too early to say.

Population trends of breeding birds in the United Kingdom since 1800

Article

Jan 1996

Building on the extensive reviews by Alexander & Lack (1944) and Parslow (1973), a scoring system is used to assess the general population trend of each species that bred in the United Kingdom during the entire 196-year period 1800-1995. This semi-quantification of qualitative assessments allows comparison of trends between species. It is recommended that revisions of the Red Data List should consider those species which have declined dramatically over historical, as well as recent, time periods. The number of species that bred in the UK apparently increased by 19%, from 194 to 230, during 1800-1995, though nearly one-third of this increase was as a consequence of introductions (intentional or otherwise).

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

Article

December 2021

Andrew Stanbury · Mark Eaton · Nicholas Aebischer · Dawn Balmer · Ilka Win

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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

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