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> Help on species accounts |
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| 3.
Help on species accounts |
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| Depending on the availability of data
(not every species is covered by each scheme), each account
consists of the following: |
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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
(see www.birdlife.net/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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Non-SPECE |
Species with a favourable European conservation
status, but with more than half of the global breeding or wintering
population concentrated in Europe |
| Non-SPEC |
Species with a favourable European conservation status, and
with less than half of the breeding or wintering population
within Europe |
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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 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 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
breeding atlases (Gibbons
et al. 1993) |
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Historical decline (in UK between
1800-1995) is assessed by literature review |
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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 (with
percentages rounded to the nearest whole number): |
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- Rapid decline: >50% population decline from
CBC/BBS, WBS or CES
- Moderate decline: 25-49% population decline from
CBC/BBS, WBS or CES
- Shallow decline: 10-24% 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 indicate conflicting trends or if the schemes are
unrepresentative of the species' total UK population
- Unknown: no information on the UK population trend
is available
- Shallow increase: 10-49% population increase from
CBC/BBS, WBS or CES
- Moderate increase: 50-99% population increase from
CBC/BBS, WBS or CES
- Rapid increase: >100% population increase from
CBC/BBS, WBS or CES
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| 3) |
Distribution maps: Provides
links to online atlas maps and tables showing numbers of occupied
squares. Data are from the First Breeding Atlas (1968-72; Sharrock
1976), Second Breeding Atlas (1988-91; Gibbons
et al. 1993) and Winter Atlas (1981/82 - 1983/84;
Lack 1986). Maps 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 Atlases
species help). |
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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 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 graphs
are calculated for each scheme. For CBC/BBS, CBC and WBS, the
graphs show a smoothed line (blue) and its 85% confidence limits
(green); for CES, Heronries Census and BBS, annual estimates
are shown (blue) together with their 85% or 95% (BBS) confidence
limits (green), and for the first two schemes a smoothed line
(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 49% (>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 are: |
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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 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 predicted 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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| 8) |
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 annual values are plotted (in
blue) with their 85% confidence intervals (in green) and a smoothed
line (red) is put through these points (see Section
2.6 for details). |
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