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| 3.
Help on species accounts |
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| The species in this report can be
accessed in any order, but the species index and drop-down list
use the taxonomic sequence established by the British Ornithologists'
Union in its British
List. The vernacular and scientific names we use are also
drawn from that list. Given this report's limited geographical
scope, we have used the British rather than the international
English names. Depending on the availability of data (not every
species is covered by each scheme), the following will be found
beneath each species heading: |
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| 1) |
Conservation listings:
First, the European conservation category is given,
according to current listings by BirdLife International in Birds
in Europe (BirdLife
International 2004). These update the original listings
of Tucker & Heath
(1994). For SPECs (Species of European Conservation Concern),
the European Threat Status is also given. The current SPEC categories
are as follows: |
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SPEC 1 |
Species of global conservation concern,
according to the latest assessments by BirdLife International
(www.birdlife.org/datazone/species/index.html) |
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SPEC 2 |
Species with an unfavourable European
conservation status, and with more than half of the global breeding
or wintering population concentrated in Europe |
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SPEC 3 |
Species with an unfavourable European
conservation status, but with less than half of the global breeding
or wintering population within Europe |
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Other species, not considered to be of European
conservation concern, and assessed as 'secure', have no SPEC
category but are placed into two further groupings: |
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Species with a favourable European conservation status, and
with less than half of the breeding or wintering population
within Europe (Non-SPEC) |
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Species with a favourable European conservation status, but
with more than half of the global breeding or wintering population
concentrated in Europe (Non-SPECE) |
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The UK conservation listing, given next, is taken
from The Population Status of Birds in the UK (Gregory
et al. 2002; see PSoB
pages). These supersede the previous Birds of Conservation
Concern listings (Gibbons
et al. 1996), and cover the period 2002–07.
There are three categories, as follows: |
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Red |
high conservation concern |
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Amber |
medium conservation concern |
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Green |
all other species (except introduced species,
which are not classified) |
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The main reason or reasons for listing as red
or amber are also given. NB: |
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SPEC 1 (globally threatened) species
are automatically red listed, and SPEC 2 or 3 species are amber
listed (unless they are introduced or a red-list criterion applies) |
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Red or amber listing may stem from
decline, localisation or importance of non-breeding as well
as breeding populations in the UK |
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Rates of population decline used
to assess red and amber listing are generally derived from CBC
results for the 25-year period 1974–99 |
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Range declines are generally calculated
from the numbers of 10-km squares occupied in the two published
breeding atlases
(Gibbons et al.
1993) |
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Historical decline (in UK over the
period 1800–1995) is assessed by literature review |
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Following the signing of the Convention on Biological
Diversity at the 'Earth Summit' in Rio de Janeiro in 1992, the
statutory conservation bodies in the UK compiled Biodiversity
Action Plans (BAPs)
for 26 rare or threatened bird species, of which 12 are covered
by this report. A BAP
review published in 2007 has concluded that 56 UK bird species
now qualify for BAPs and has recommended that certain subspecies
(e.g. Fair Isle and St Kilda Wrens) should now be included.
This report covers 31 of those species.
Where a UK BAP exists, we give the link to the latest available
version. You will find onward links, for example to local BAPs
for that species. For species newly nominated, we record that
a BAP is 'in preparation'. |
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| 2) |
Long-term trend: This
summarises the trend in population size since 1975 from WBS
data, 1984 from CES data, or 1967 from CBC/BBS, with reference
to any CBC/BBS, WBS or CES data that may be tabulated. If there
are no data available from these schemes, any assessment of
trends covers the period since about the mid 1960s, but may
also take historical data into account. Increases and declines
that are qualified as 'shallow', 'moderate' or 'rapid' are generally
statistically significant. The following terms are used: |
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- Rapid decline: >50% population decline from
CBC/BBS, WBS or CES
- Moderate decline: 25–50% population decline
from CBC/BBS, WBS or CES
- Shallow decline: 10–25% population decline
from CBC/BBS, WBS or CES
- Decline/Increase: information has been derived
from other sources
- Probable/Possible increase/decline: as above, but
the information is not as certain - see the status summary
for reasons
- Stable/Fluctuating, with no long-term trend: no
overall change, or change <10%
- Uncertain: where the information from two monitoring
schemes conflicts or if the data are unrepresentative of
the species' total UK population
- Unknown: no information on the UK population trend
is available
- Shallow increase: 10–50% population increase
from CBC/BBS, WBS or CES
- Moderate increase: 50–100% population increase
from CBC/BBS, WBS or CES
- Rapid increase: >100% population increase from
CBC/BBS, WBS or CES
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| 3) |
UK population size:
Periodic reports on population sizes of birds in Britain and
in the UK, for the breeding season and for winter, are agreed
by the Avian Population Estimates Panel (APEP), on which BTO,
GCT, JNCC, RSPB and WWT are repesented. Extracts from the Panel's
second report (Baker et
al. 2006) are given for each of our species, with a
shortened reference (APEP06). The second edition of Birds
in Europe (BirdLife
International 2004) was published while APEP06 was in preparation.
Their figures are also given, referenced as BiE04. The units
and reference year (or period) is given for each estimate, and
where possible its derivation is also described briefly or referenced.
BiE04 and APEP06 estimates are usually identical, but may differ
because: |
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- one or other is updated to a new reference year
- the two publications apply different rules for inclusion
of introduced species
- BiE04 figures include the Channel Islands (but for most
species this has no effect on the estimate)
- different methods of rounding or range estimation have
been applied to the same original data
- sources used for BiE04, but not APEP06, included papers
in preparation
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Information too recent to have been included in
either of these publications is also given, pending ratification
by APEP. Readers should note that the wide ranges given for
many species reflect the considerable uncertainty that applies
to all but a few of the current estimates. The application of
distance sampling methods to BBS data (Newson
et al. 2005), or future surveys, including the
current 2007–11
Atlas, may well result in substantial challenge to the presently
accepted figures. |
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| 4) |
Status summary: This section provides
a brief summary of the trends detailed for the species and indicates
why such changes might have occurred, with reference to any
published information, if this is known. |
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| 5) |
Population trend graphs:
The first, large graph shows the most representative long-term
trend in abundance for the species, and is followed after the
table by further graphs from other schemes, including BBS graphs
for separate UK countries, as available. If no suitable long-term
trend is available then the BBS trend for the UK is shown. Methods
(Section 2) provides details about how the trend
data are calculated for each scheme. For BBS, CBC/BBS, CBC,
WBS and CES, the graphs show a smoothed line (in blue) and its
85% confidence limits (in green); for the Heronries Census,
annual estimates are shown in blue, 85% confidence limits in
green, and a smoothed trend in red. |
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| 6) |
Population trends table: This table
provides details of summarised percentage changes in population
size, over the maximum period from each source, and from the
past 25 years, 10 years and 5 years, where these figures are
available. Further columns indicate the years included, the
average number of census plots included in the analysis for
each year, the percentage change (an increase if presented with
no sign) and the upper and lower 90% confidence limits of that
change. Where the confidence interval does not include zero
change, population declines are regarded as statistically significant.
The 'Alert' column indicates where a statistically significant
population decline is estimated to be of 50% or more (>50) or
between 25% and 50% (>25) (see Alerts,
Section 2.8 for further details). The 'Comment'
column lists any caveats that must be considered when interpreting
the estimates. The caveats include: |
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- Small sample: For CBC, WBS and CES data, a mean
sample size of less than 20 (but more than 10) census plots
was available; for BBS data from individual countries, a
mean sample of less than 40 (but more than 30) plots was
available.
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- Unrepresentative?: Where joint CBC/BBS trends are
reported, the trends are always considered to be representative
for the region concerned.The CBC data may inadequately represent
the population as a whole. This judgment was made either
because the species' average abundance in 10-km squares
containing CBC plots was less than that in other occupied
10-km squares, as measured by Breeding Atlas timed counts
or frequency indices (Gibbons
et al. 1993), or, where these figures could
not be calculated, on expert opinion.
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| 7) |
Productivity graphs: Graphs from
Constant Effort Sites Scheme or Nest Record Scheme data illustrate
trends in productivity. For NRS data, annual means (averages)
are shown in green, with error bars to denote ±1 standard error;
quadratic or linear regression lines (in black) and the upper
and lower 95% confidence limits of these lines (in blue) are
also shown. For CES data, the smoothed trends are plotted (in
blue) with their 85% confidence limits (in green) (see Section
2.6 for details). |
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| 8) |
Productivity trends table: This
provides details of changes in productivity since 1968 (or a
more recent year, depending on the availability of data). It
lists the period of years concerned, the mean annual sample,
the type of trend ('curvilinear' is for a significant quadradic
trend, 'linear' is for a significant linear trend, 'none' is
where the linear trend is not significantly different from horizontal),
the modelled values (from the appropriate regression) for the
first and last years and their difference (where the trend is
significant), and any caveats that must be considered when interpreting
the data. Changes are presented either in the units given or
as percentages, and are increases unless a minus sign is shown.
The caveat 'Small sample' is given when the mean number
of nest record cards contributing annually was in the range
10–30, or when the mean annual number of CES plots recording
the species was less than 20 (but more than 10). |
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| 9) |
Additional information: Provides
links to atlas maps and tables from previous atlas surveys,
and the relevant pages of BirdFacts, BirdTrack and Garden BirdWatch,
as available, from the BTO web site. Atlas maps from earlier
surveys are not yet available online for Red-throated Diver,
Goosander, Hen Harrier, Buzzard, Hobby and Peregrine, for which
some of the original data were confidential (see previous
atlases species help). |
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