COUNTRYSIDE BIRD SURVEY REPORT - BIRDWATCH IRELAND
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Countryside Bird Survey Report
In total, 402 1km squares were The Common Bird Index (CBI) was
surveyed between 1998 and 2019, all based on 50 common and widespread
of which have been surveyed in two or breeding birds which are monitored
more years. The number of squares as part of the CBS. The indicator has
covered in any one season ranged increased overall (1998 – 2019), with
from 259 in 1998 to 329 in 2019. the 2019 index at 126% of the base-
line index (2000), meaning that, on
Species trends are reported for bird average, the population size of the
species recorded in 30 or more species included in the indicator
squares per year on average. Within has increased by 26 per cent.
the current reporting period, a total
of 48 bird species exceeded this The Common Farmland Bird Index
Summary threshold comprising 36 residents (CFBI) was based on 18 common and
and 12 summer migrants. widespread breeding farmland birds
The Countryside Bird Survey (CBS) which are monitored by the CBS.
has been in operation since 1998. Its Wren (Troglodytes troglodytes) The CFBI in 2019 was 111% of the
primary aim is to monitor breeding was the most widespread species baseline index in 2000, representing
bird populations in the Republic occurring in 94% of squares, followed an increase relative to the baseline.
of Ireland. by Blackbird (Turdus merula), Robin Among the constituent farmland bird
(Erithacus rubecula), and Chaffinch species, increases were shown in ten
A random sample of 10km squares (Fringilla coelebs), that occurred in species and declines in a further six
was selected, and within each, the at least 90% of squares. Average species, while the remaining two
most south-westerly 1km square was abundance was highest for Rook species were stable.
surveyed twice during each breeding (Corvus frugilegus) followed by Wren
season. Bird counts were carried out and Starling (Sturnus vulgaris). Importantly, despite the largely
along two roughly parallel 1km positive trends for many species
transects in each square. Overall, 29 species showed popula- monitored through the CBS, both the
tion increases, seven species declined, species trends and the wild bird
This CBS report presents a summary of while the remaining 12 species have indicators reported here should be
bird species trends within the CBS relatively stable trends. Greatest viewed with caution and seen against
over the 22-year period from 1998 to increases were seen in Blackcap (Sylvia the backdrop of drastic declines that
2019 inclusive. For the first time, atricapilla) and Goldfinch (Carduelis occurred in the 1970s and 1980s in
this report also includes wild bird carduelis). Greatest declines were in Ireland and Britain, before the CBS
indicators for the Republic of Ireland, Greenfinch (Chloris chloris) and Grey began. In many cases, population
namely the ‘Common Bird Index’ and Wagtail (Motacilla cinerea). The increases for species, albeit welcomed,
the ‘Common Farmland Bird Index.’ remaining declining trends were for should be viewed as the recovery of
Swift (Apus apus), Kestrel (Falco populations rather than
tinnunculus), Stonechat (Saxicola increases per se.
torquata), Rook and Magpie (Pica pica).
Report Number 6 BirdWatch Ireland: Unit 20 Block D, Bullford (BirdWatch Ireland), Niall Ryan (Department of
Business Campus, Kilcoole, Co. Wicklow, A63 Agriculture, Food and the Marine) and John
© BirdWatch Ireland 2020. RW83. O’Halloran (University College Cork) who chairs
the group.
This publication should be cited as: National Parks & Wildlife Service (NPWS): 90 King
Citation: Lewis, L. J., Coombes, R, H., Burke, B., Street North, Dublin 7, D07 N7CV. CBS Coordinator: Dick Coombes
Tierney, T. D., Cummins, S., Walsh, A. J., Ryan, N. (rcoombes@birdwatchireland.ie)
& O’Halloran, J. 2020. Countryside Bird Survey The CBS Steering Group includes David Tierney, CBS Programme manager: Lesley J. Lewis
Report 1998-2019. BirdWatch Ireland. Wicklow. Sinéad Cummins and Alyn Walsh (NPWS), Dick (ljlewis@birdwatchireland.ie)
Coombes, Brian Burke and Lesley J. Lewis NPWS Project officer: Sinéad Cummins
Design & layout by Michael O’Clery. (Sinead.Cummins@chg.gov.ie).
The Countryside Bird Survey (CBS) is coordinated
by BirdWatch Ireland and funded by the National
Parks & Wildlife Service (NPWS).
Cover picture: Grey Wagtail by Dick Coombes.
Introduction
Dick Coombes
The distribution of terrestrial breeding
birds in Ireland was first described in
a breeding bird atlas carried out
between 1968 and 1972 (Sharrock
1976). A second breeding bird atlas
survey carried out between 1988 and
1991 (Gibbons et al. 1993) showed
that significant range contractions
had occurred over the intervening
20-year period which had obvious
implications for changes in population
levels (Crowe et al. 2017). These
declines coincided with a period of
increased agricultural intensification
and land use change. Similar declines Collared Dove.
in bird populations occurred through- A species, which only began colonising Ireland in the late
out Europe over the same period and 1950s, has steadily increased since the CBS began in 1998.
were attributed to agricultural
intensification brought about by an changes in bird numbers based on a sensitive to specialised habitats, and
increased demand for agricultural random selection of 1km sample respond quickly to the changes to
productivity following the Second plots, stratified by region, surveyed their environments (Gregory et al.
World War (e.g. Krebs et al. 1999). from year to year (Lewis et al. 2019). 2003; van Strien et al. 2012). Indicator
While the two bird atlases, and a third The resulting data are the species species have been used for decades
one carried out between 2007 and diversity and species abundance of as a way of assessing environmental
2011 (Balmer et al. 2013), flagged each survey square each year. Follow- conditions (Thomas 1972). Wild birds
changes in the status of some species ing statistical analysis, a series of an- satisfy many of the criteria of being
over time, they focused mainly on nual indices are produced for each useful biodiversity indicators in that
distribution. Abundance was recorded individual bird species based on the they occur high in food chains, are
in the second and third atlases, results of each annual survey. These sensitive to environmental change,
providing indications of population indices relate the population in a are widespread, diverse and mobile,
changes over that twenty-year period given year to a ‘baseline’ – the first and are relatively easy to census
but as these atlases were carried out year that data are available (1998 in and collect data for, through well
at twenty-year intervals, there was CBS), which is given a value of 100. developed and standardised
clearly a need for a long-term Thereafter, the index expresses the methodology (Gregory & van
monitoring programme to track population as a percentage of this Strien 2010).
changes of terrestrial breeding birds ‘baseline’. The word ‘index’ is derived
on an annual basis. The Countryside from the Latin indicare, meaning to A wild bird indicator is a composite
Bird Survey (CBS) was therefore ‘point out’ or ‘to show’, hence the index whereby the indicator shows
initiated in 1998 with the primary population index shows how the the year-to-year fluctuations in
objective of monitoring the trends of population is faring over time i.e. the population trends across all species
common and widespread breeding population trend for each species. that are included. Thus, the index is
bird species in the Republic of Ireland the average trend of a group of
(Crowe et al. 2010). The CBS has been In addition to individual species species, generally grouped by country,
undertaken during all years since 1998 indices, annual indices can also be region, habitat type or guild in a
with the exception of 2001 and 2020, used to produce ‘wild bird indicators’ standard way. This index then serves
when Foot-and-Mouth and Covid-19 (e.g. Gregory et al. 2003; Gregory et al. to indicate the state of bird
restrictions respectively, prevented 2005; Gregory & van Strien 2010). populations within these broad
survey work. Indicators are a useful way of habitats/groups.
presenting complex information as
The CBS is an annual survey that is visual summaries (Gregory et al. 2003). Wild bird indicators were first
underpinned by the efforts of around To be effective, biodiversity indicators produced in the UK in 1999 using data
225 mostly volunteer, observers each should be quantitative, scientifically mostly from the Common Bird Census,
year. The survey aims to measure credible, ecologically relevant and the Breeding Bird Atlases, and the
1
Seabird Monitoring Programme.
Richard T. Mills
Within the Republic of Ireland, the CBS
has produced indicators previously for
farmland and countryside birds and
these data have been used by the
Environmental Protection Agency
and the Central Statistics Office for
environmental reporting. Importantly,
CBS data are provided to the Pan-
European Common Bird Monitoring
Scheme (PECBMS) for European Wild
Bird Indicators and the PECBMS
common bird indicators are part of
the Indicators of Sustainable
Development of the EU, while the
European farmland bird indicator has
been accepted as biodiversity
indicator for EU´s Structural Indicator,
amongst other policy purposes.
This 2020 CBS report represents a
summary of bird species trends within
the CBS over the 22-year period from
1998 to 2019 inclusive. For the first
time, this report also includes wild
bird indicators for the Republic of
Ireland, namely the ‘Common Bird
Index’ and the ‘Common Farmland
Bird Index.’
Methods
At the commencement of the survey, Greenfinch.
the Republic of Ireland was divided Steadily declining – believed to be due to the
into eight regions, based on the parasitic organism Trichomonas gallinae,
administrative divisions of the which affects the birds’ digestive system.
National Parks and Wildlife Service at
that time. Ten km squares (based on
the Irish National Grid) were randomly each 1km in length, about 500m activity, but to avoid concentrated
selected within each region for survey apart, and about 250m from the edge song activity at dawn. Observers are
coverage. For each 10km square of the square (line-transect method). also encouraged to record only adult
selected, the 1km square at the Two bird-recording visits to each birds they see or hear as they walk
extreme south-west corner is then survey square per year are under- along their transect routes. Bird
surveyed. Those squares with less than taken. These visits are timed so that counts in heavy rain, poor visibility,
50% land, for example coastal areas or the first is in the early part of the or strong winds are discouraged.
lake shores, were excluded, leaving breeding season (April to mid-May) For further details of the survey
some 700 possible survey squares. and the second at least four weeks design, please refer to Lewis et al.
The survey aims to achieve coverage later (from mid-May to the end of 2019. For full details of the data
of the same 1km squares every year, June). This timing captures the analyses used to produce both
ideally by the same observer, although abundance of residents and early individual species indices and trends
there is some turnover of survey migrants, which tend to be more as well as wild bird indicators, please
participants. There is a target of a easily detected during first visits, see Appendix 1.
minimum of 300 squares to be and later migrants, which are more
covered each year. abundant during second visits. The Latin names of species that
Observers are asked to begin their underwent analysis are given in
Within each square, the ideal survey counts between 06.00 and 07.00 Table 1, other Latin names are given
route comprises two parallel transects, hours to coincide with maximum bird at first mention in the text.
2
Results
Coverage
The CBS continues to be undertaken
by a combination of BirdWatch Ireland
volunteers and professional staff of
the National Parks and Wildlife Service
and BirdWatch Ireland. A total of 683
observers have taken part in the CBS
between 1998 and 2019.
In total, 402 1km squares were
surveyed between 1998 and 2019
(Figure 1), all of which have been
surveyed in two or more years. The
number of squares covered in any
one season ranged from 259 in 1998
to 329 in 2019. Overall, 14% of squares
were covered in all 21 years, 68% of
squares were covered in at least 15
years, and 91% of squares in 10 years
or more.
Species trends
The CBS is largely targeted at
monitoring species with widespread
distributions across the island. The
large number of sample plots
surveyed in the CBS (over 300
annually) ensures that all common
and widespread breeding species
are surveyed across a wide range of
habitats and geographical locations.
Species recorded in 30 or more 1km Figure 1. Map showing survey coverage during the CBS between 1998 and 2019, illustrating the
squares per year are included in trend eight sampling regions and also showing the extent of coverage within each ranging from red (1-7 years),
analyses. Within the current reporting blue (8-14 years) and green (15-21 years).
period, a total of 48 bird species
exceeded this threshold (and there-
Meadow Pipit.
Dick Coombes
fore robust estimates could be derived
for them), comprising 36 residents Badly hit in the cold winters between 2010 and
and 12 summer migrants (Table 1). 2012, but numbers have bounced back well.
Two species reported previously
(Sparrowhawk (Accipiter nisus) and
Stock Dove (Columba oenas) now
occur in less than 30 squares per
season and were excluded from
analyses.
Of the total 48 species listed in Table 1,
17 species occurred on average in
greater than 200 squares. Wren was
the most widespread species
occurring in 94% of squares, followed
by Blackbird, Robin, Chaffinch, that all
3
Table 1. Species recorded in 30 squares or more during the CBS between 1998 and 2019, indicating the mean number and proportion of squares in which each species was recorded, mean abundance per square and the mean annual change (trend). Where the trend has changed when compared with the last report (to 2017), an indication of the direction is given. Red- and amber-listed species of Birds of Conservation Concern in Ireland (BoCCI) are also indicated. Significant trends are represented by asterisks. A ** indicates a highly significant trend (p
occurred in at least 90% of squares.
Mean abundance was highest for
Rook (average 26 per square),
followed by Wren and Starling.
Most species assessed by the CBS are
currently exhibiting trends for
moderate increases in population
size (Figure 2).
A total of seven species declined
between 1998 and 2019, the largest
declining trends observed were for
Greenfinch and Grey Wagtail, the
latter a red-listed species on the Birds
of Conservation Concern (Colhoun &
Cummins 2013) (Figure 3). The Figure 2. Percentage of species exhibiting declining, stable and increasing trends.
remaining declining trends were for
Swift, Kestrel, Stonechat, Rook and
Magpie. The largest observed When compared to the previous species (Rook) has dis-improved, from
increases were for Blackcap and report (Crowe et al. 2017), the status of stable to a moderate decline (Figure
Goldfinch (strong increase), with a eight species has improved, namely 5). The trends for three species
further 27 species having moderate Skylark, Mistle Thrush, Robin and previously reported to have declined
increases over time, the largest being Meadow Pipit (moderate decline to following the cold winters of 2009/10
for Chiffchaff and Collared Dove stable), and Raven, Long-tailed Tit, and 2010/11 (Skylark, Meadow Pipit
(Figure 4). A further 12 species have Starling and Redpoll (stable to and Goldcrest), are now stable. Skylark
stable trends throughout the CBS. moderate increase). The status of one and Meadow Pipit have moved from a
Figure 3. Trends for species that have shown the greatest declines 1998-2019.
5
Figure 4. Trends for species that have shown the greatest increases 1998-2019.. Figure 5. Trends for a selection of species 1998-2019. 6
moderate decline to stable since the The Common Farmland Bird Index Among the constituent farmland bird
previous report, as above. The status (CFBI) was based on 18 breeding species, increases were shown in ten
of Song Thrush remains stable and this farmland birds which are monitored species and declines in a further six
species appears to have recovered by the CBS (Appendix 1). The CFBI in species, while the remaining two
fully since a downturn around 2019 was 111% of the baseline index species were stable (Figure 6).
2010/11. The trend for Stonechat in 2000, representing a marginal
remains a moderate decline, although increase relative to the baseline.
the species population index has
recovered well since 2010/11. While
the trend for Mistle Thrush is stable, Dick Coombes
numbers in the recent two years (2018
and 2019) have increased substantially
above baseline level (Figure 5).
Indicators
The Common Bird Index (CBI) was
based on 50 common and widespread
breeding birds which are monitored
as part of the CBS. The indicator has
increased overall (1998 – 2019),
with the 2019 index at 126% of the
baseline index (2000), meaning that,
on average, the population size of the
species included in the indicator has
increased by 26 per cent. Overall, Mistle Thrush.
there have been increases in 29 A species in moderate
species, declines in eight species with decline up to 2016 but
the remaining 13 constituent species now stable.
showing stable trends throughout the
course of the CBS (Figure 6).
Figure 6. The Common Bird Index and Common Farmland Bird Index 1998 – 2019.
7
Brian Burke
Blackcap
Dramatic increase continues
across Ireland.
Discussion showing stable trends is slightly (Colhoun & Cummins 2013).
fewer at 12 (compared to 15). However, positive CBS trends for
The data gathered over the 22 years several farmland birds, such as some
of the CBS have provided us with a Goldfinch and Blackcap both of those mentioned above, need to be
valuable picture of how a large continue to thrive – these are the only viewed with caution and seen against
number of our common and species classed as showing a strong the backdrop of drastic declines that
widespread breeding birds are faring. increase. Goldfinches may be occurred in the 1970s and 1980s in
As the time series of the survey benefitting from an increased amount Britain and Ireland, before the CBS
continues to extend, the results of provisioned food in gardens during began (Donald et al. 2002, Balmer et al.
become more robust and relevant. winter while the increases in Blackcap 2013). These declines, in some cases at
Overall, most species are doing well, are believed to be related to climate least, can be attributed to changes in
showing either increasing or stable change. Of particular note is the farming methods. Yellowhammer, for
trends. When compared to the last on-going positive trend pattern for example, although stable over the 22
report (Crowe et al. 2017), three more five finch species and Reed Bunting years of CBS, was already at a very low
species are showing increasing trends and the continuing stable trend for base in 1998, when the CBS was
(29 compared to 26) and there are five Yellowhammer, a Red-listed species launched. The 2007-2011 bird atlas
fewer species showing declines (7 under BoCCI (Birds of Conservation (Balmer et al. 2013) showed that
compared to 12), while the number Concern in Ireland 2014-2019 Yellowhammer had contracted its
8range on the island of Ireland by 61% Similar caution needs to be extended was less than half its value at the start
over the preceding 40 years and is to the wild bird indicators. The point of 1970, with rapid declines from
now mainly found in the cereal common bird and common farmland 1975 to 1985 attributed to changes in
growing regions of the south-east. indicators are composite indicators farmland management (Hayhow et al.
Cuckoo too, although stable in the designed to show broad trends in the 2017).
CBS, suffered a 26% range reduction constituent species. Being used as a
in the same 40-year span, probably proxy for the state of biodiversity, Over the lifetime of the CBS, the most
due to agricultural intensification indicators are often used to indicate sudden and indeed steepest declines
depleting its main food – caterpillars. the status of bird populations within recorded were for Stonechat, Grey
Although these may be extreme the broad habitats/groups used. Wagtail and Meadow Pipit in the 2010
examples, there are likely to be other However, given the largely positive and 2011 seasons. The winters preced-
farmland species which started at a trends of species within the CBS, the ing both these breeding seasons had
similar low base in the CBS, so any indicators generally follow suit, and as been particularly harsh and it is
gains they are making, albeit above, the increasing indicators are considered that the sustained cold
welcomed, should perhaps be viewed indicative of recovering populations in weather was the cause of the
as the restoring of populations to many of the constituent species, and heavy losses.
former levels, rather than increases not true increases. As an example, the
per se. UK farmland bird indicator in 2016
Richard T. Mills
Yellowhammer.
Highly dependent on arable farmland,
especially cereal growing areas. Numbers
stable despite considerable losses in the
decades before the CBS.
9A similar sharp, though less severe, such species which is steadily the Kestrel’s range in 40 years, but
pattern of decline was found at that declining. Depleted availability of interestingly also a shift in abundance
time in several other species including aerial insects both during the breed- from the northern half of the country
Skylark, Robin, Song Thrush, Mistle ing season and on its migration route to the south and south-west. Of note
Thrush, Wren and Goldcrest. All these and wintering grounds may be a is that Buzzards are likely to be
species have since staged recoveries factor in its decline, but the loss of included in the next trend reporting
to varying degrees. It is interesting to traditional nest sites in old buildings as they are now on the cusp of the
note that the cold winter weather due to restoration work is also consid- 30-square threshold for inclusion in
seems to have had greatest impact ered to be contributing to this iconic trend analyses.
on resident insectivores and/or small- summer bird’s decline (e.g. Whelan et
bodied species. al. 2019). The trend for Kestrel has also The decline in Rook numbers has
been steadily downward, the reasons been gradual but ongoing and may
Species which have shown long-term, are unclear. Perhaps competition from bear out anecdotal reports of long-
steady declines are of greater concern the ever-increasing population of established rookeries diminishing in
than those that may succumb to Buzzard (Buteo buteo) is a contributing size or even disappearing altogether
severe winter weather and subse- factor. The latest bird atlas (Balmer et in recent years. Changes in agriculture
quently bounce back. Swift is one al. 2013) shows a 6% contraction in may be a factor here too.
Buzzard.
Increasingly being recorded in the
CBS, but not quite in a sufficient
number of squares to be accurately
monitored by CBS yet.
Dick Coombes
10The downward trend in Greenfinch On the plus side, it is encouraging to Acknowledgements
has continued since it began in 2008. see that, with the exception of Swift,
Studies in Britain found that the all our regular summer migrants are The Irish Countryside Bird Survey (CBS) is
parasite trichomonosis was doing well, with four species of funded by the National Parks and Wildlife
responsible for a major crash in the warbler and House Martin showing Service (Department of Housing, Local
Greenfinch population, which began increasing trends, while Swallow, Sand Government and Heritage) and coordinated
in 2005 (Robinson et al. 2010). The Martin, Wheatear, Grasshopper by BirdWatch Ireland. The CBS Steering
disease appears to have gained a Warbler and Sedge Warbler are Group is comprised of Dick Coombes
foothold in Ireland and it is the likely stable. However, counts of summer (National Coordinator), Lesley Lewis and
cause of the downward CBS trend. In migrants can fluctuate considerably Brian Burke of BirdWatch Ireland, David
Tierney, Sinéad Cummins and Alyn Walsh of
the last CBS report, Stock Dove, a from year to year, most likely in
the National Parks and Wildlife Service, John
species closely associated with arable response to adverse weather either O'Halloran of University College Cork, and
farmland, had shown a steady decline on the African wintering grounds Niall Ryan of the Department of Agriculture,
up to 2016 (Crowe et al. 2017). It is or on migration. Food and the Marine.
now recorded in fewer than 30
squares annually and therefore falls The CBS continues to be a valuable The success of the survey relies on the hard
below the threshold for monitoring in tool in monitoring the state of our work, passion and time dedicated by the
the CBS. This in itself is worrying and breeding countryside birds and helps numerous volunteer fieldworkers, and staff
of NPWS and BWI that carry out visits to
reflects that the ongoing trend to highlight pressures and threats on
squares each year. We thank all of you.
continues downwards. an ongoing basis to both birds and A list of all valued participants of the CBS
their habitats. since 1998 is shown in Appendix 2.
Lewis, L. J., Coombes, D., Burke, B., O’Halloran, J.,
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11Appendix 1 Data analyses – species trends Population change is shown in the
The total numbers of adult birds of form of annual indices, where the
Survey design and each species detected in each 1km result from the first season (1998) is
square were calculated for each year. constrained to a value of 100, and
field methods
The maximum of the two counts results for all other years are
The CBS is based on a random (from early and late visits) was used expressed relative to this baseline.
stratified sampling approach. At the as the annual measure of relative A constant rate of decline is
commencement of the survey, the abundance for each species. Annual exponential when illustrated. For
Republic of Ireland was divided into population indices were calculated example, if a population is declining
eight regions, based on the adminis- using TRIM (Trends & Indices for by 50% each year, then if the initial
trative divisions of the National Parks Monitoring Data), a programme index is 1, the index at timepoint 2 is
and Wildlife Service at that time. used for the analysis of time series of 0.5, and at timepoint 3 is 0.25. If the
These regions varied in size, and counts with missing observations population doubles each year, then
each contained between three and (Pannekoek & van Strien 1996). the index values for the respective
four counties. Ten km squares (based Counts are modelled as a function of timepoints are 2, 4 and 8. Index
on the Irish National Grid) were square (site) and year effects, with values are thus measures of relative
randomly selected within each interpolated estimates for site-year abundance for a species, and usually
region for coverage. Those squares combinations with missing data. The the relationship between this and
with less than 50% land, for example stratified sampling design results in the absolute abundance is
coastal areas or lake shores, were unequal representation of regions unknown.
excluded, leaving some 700 possible across Ireland, so annual counts
survey squares. For each 10km were weighted by the inverse of The mean annual change was
square selected, the 1km square at the proportion of the area of each calculated as the slope of the line of
the extreme south-west corner is region that was surveyed that year. best fit through the annual indices
then included for possible survey. and was extrapolated across the
The survey aims to achieve coverage Population trends for species time series 1998-2019 to generate
of the same 1km squares every year, occurring in a mean of 30 or more modelled values assuming a
ideally by the same observer, squares over the duration of the linear fit.
although there is some turnover of survey were estimated by examining
survey participants. Within each the overall rate of annual change, Data analyses – wild bird
square, the ideal survey route precision below this threshold indicators (index)
comprises two parallel transects, considered to be low (Joys et al.
each 1km in length, about 500m 2003). A wild bird indicator is a composite
apart, and about 250m from the index whereby the indicator shows
edge of the square. However, for the year-to-year fluctuations in
practical reasons there is sometimes
deviation from the ideal route
(Crowe et al. 2010). Each 1km
transect is divided into five 200 m
sections, at which level all
information is collected. Three visits
to each survey square per year are
undertaken. During a reconnais-
sance visit, the transect routes are
planned and habitat information
recorded. Habitat data are recorded
using codes from an established
hierarchical system common to a
range of bird surveys in the UK
Dick Coombes
(Crick 1992). Bird counts are
Whitethroat.
undertaken on the second and
A summer migrant on the increase – one of
third visits.
four warbler species showing upward trends.
12population trends across all species indicator. This is the same as saying Table A1. Species included in composite
that are included. The Common Bird that, on average, there are 10% more indicators - The Common Bird Index (CBI) and
Index (CBI) was based on 50 individuals in the population of each Common Farmland Bird Index (CFBI).
common and widespread breeding species.
birds, while the Common Farmland Species CBI FBI
Bird Index (CFBI) was based on 18 • Conversely, a decrease in the Sparrowhawk 4
common and widespread breeding indicator from 100 to 90 would Kestrel 4 4
farmland birds which are monitored mean that the average change in Pheasant 4 4
by the CBS (Table A1). Thus, the each species index included in the Feral Pigeon 4
indicator is -10%. Stock Dove 4 4
index is the average trend of a group
Woodpigeon 4 4
4
of species, grouped by, in this case • It is important to remember that Collared Dove
4
(1) common and widespread the indicator is an aggregate of Cuckoo
4
breeding birds, and (2) common individual species indices and hence Swift
4
farmland birds. Note that despite the masks a lot of variation among Skylark
trend for Sparrowhawk and Stock individual species and groups of Sand Martin 4
Dove not being reported because species. Therefore, increases in some Swallow 4 4
these species now occur in less than species and decreases in other House Martin 4
30 squares per year (29), they were species can balance one another. Meadow Pipit 4
included in the CFBI to provide Grey Wagtail 4
consistency with previous indicator • An increasing indicator does not Pied Wagtail 4 4
calculations. mean that the majority of species Wren 4
included has increased because the Dunnock 4
The composite index was calculated index can be strongly influenced by Robin 4
as the geometric mean of all the a large magnitude change in one or Stonechat 4 4
individual indices of the constituent Wheatear 4
more of the species included.
species, with no weightings - so that Blackbird 4
• The indicator treats every species Song Thrush 4
each species has the same relative
as equivalent and does not weight Mistle Thrush 4
4
effect on the indicator. The geometric
trends by the population size of Grasshopper Warbler
4
mean is used to ensure that a
Sedge Warbler
each species. The use of equal
4
doubling in the population index of Whitethroat
weights across species ensures
one species (e.g. 100 to 200) is Blackcap 4
4
balanced by a halving (e.g. 100 to 50). changes in the indicator are not
Chiffchaff
4
completely dominated by the trends
Willow Warbler
4
The indicators serve to indicate the in the most common species. Goldcrest
state of bird populations within the Long-tailed Tit 4
• The geometric mean is used in
wider countryside. However, it Coal Tit 4
4
should be borne in mind that they calculations because it is less
Blue Tit
4
are based on data from common influenced by outlying single values
Great Tit
4 4
and widespread breeding bird (outliers). In this case the use of the Magpie
species only. Certain species arithmetic mean is inappropriate Jackdaw 4 4
groupings, for example, breeding because species that are increasing Rook 4 4
wading birds and birds of prey are by a constant proportion per year Hooded Crow 4 4
not included in the Common carry greater weight than species Raven 4
Farmland Bird Index and the that are decreasing at the same Starling 4 4
indicator cannot adequately proportional rate (Buckland et al. House Sparrow 4 4
represent these species. 2005). Thus, the geometric mean is Chaffinch 4 4
more appropriate because outliers Greenfinch 4 4
in population increases are relatively Goldfinch 4 4
4 4
Key points to understanding
common. The geometric mean is Linnet
4
the indicators
also invariant to the choice of Redpoll
• An increase in the indicator from weights, avoiding the need to Bullfinch 4
Yellowhammer 4 4
100 to 110 would mean an average specify subjective weights that
Reed Bunting 4
change of +10% in each of the have no rigorous scientific basis
species indices that make up the (Buckland et al. 2005).
13Marie Foley, Pat Foley, Ciaran Foley, Joe Foley, Aidan Caroline Murphy, Kate Murphy, Kevin Murphy,
Appendix 2 Foley, Sarah Jane Fortune, Denise Foulkes, Jim Fox, Jacintha Murphy, Michael Murphy Sandra Murphy,
John Fox, Eddie Foyle, Stephen Franck, Kathryn Pat Murphy, Evelyn Murray, Tony Murray, Georgia
We thank all of the Freeman, Patricia Fuentes , Janice Fuller, Debbie
Gaffney, Laura Gallagher, Tara Gallagher, Joanne
Murray, Gerard Murray, Mieke Muyllaert, Tony Nagle,
Erin Neary, Tom Neenan, Rev David Nesbitt, Daniel
dedicated observers who Gallagher, Colin Gallagher, Vincent Gallagher, Paul Neville, Willie Newe, Aine Ni Shuilleabhain Róisín
have participated in the CBS Galvin, Rory Gardner, Emmet Gavin, Emer Giddy, Nigfhloinn, Des Nolan, Jane Nolan, Albert Nolan, Jim
Girion Girion, Emma Glanville, Adrian Glasgow, Noonan, Maura Noonan, Michael Noonan, Gabriel
Joe Adamson, David Anchell, Peter Anderson, Eugene Breeda Gleeson, Andrew Glenn-Craigie, Michael Noonan, Mark Norris, Kevin Nunan, Laura Nuttall,
Archer, Tina Aughney, Craig Ayres, Paul Baker, Tony Glynn, Pauline Goggin, Ruairi Goodwin, Ruairi Michael Oates, John O'Boyle, Cathal O'Brien, Seamus
Baldock, Enda Bannon, Jessica Barrett, Mick Barry, Goodwin, Tim Gordon, Jo Gordon, T. Gordon, Jackie O'Brien, Margaret O'Brien, Irene O'Brien, Philip
Marie Bartlett, Penny Bartlett, Colin Barton, H. Gorman, Brian Gormley, Brian Gormley, Kieran Grace, O'Carroll, Séamus Ó'Ciarduáin Michael O'Clery,
Baumann, Myrna Beardsworth, Michael Bell, Jenny Patrick Graham, Nick Gray, Elena Green, Jim Greene, Micheal O'Coileain Dan O'Connell, Sr Mary O'Connell,
Benito, Bernadette Bergin, Dominic Berridge, Simon Roger Greene, Tim Griffin, Michael Gunn, John Laurence O'Connell, Kevin O'Connell, Peadar
Berrow, Eddie Berry, Tony Berry, Sinead Biggane, Ann Guthrie, Josephine Guthrie, Thomas Gyorffy, D. O'Connell, Jack O'Connell, Michael O'Connell,
Bingham, Sam Birch, Brendan Black, David Bluck, Haisley, Frank Halbert, Lesley Hambrook, Billy Brendan O'Connor, Brian O'Connor, Charlie O'Connor,
Helen Boland, Hans Bomhoff, Richard Bono, Heather Hamilton, John Hand, Hugh Hanley, Josephine Fergal O'Connor, Kate-Marie O'Connor, Daire
Bothwell, Neil Bourke, Aoife Boyd, Fintan Bracken, Hanley, Vincent Hanlon, Cathryn Hannon, Gordon O'Criodain, Aonghus O'Donaill, Padraig O'Donnell,
Fran Brady, Marion Brady, Dermot Breen, Sean Breen, Hardwicke, Michael Harkin, Niall Harmey, Yvonne Mick O'Donnell, Declan O'Donnell, Ger O'Donnell,
John Breen, Margaret Brennan, Martin Brennan, Niall Harrington, Seamus Hassett, Niall Hatch, Dennis John O'Donnell, Tim O'Donoghue, Seamus
Brennan, Derek Brennan, Bro Angelo, Thomas Broe, Hawke, Don Healy, Michele Healy, Clare Heardman, O'Donoghue, Padraigin O'Donoghue, Barry
Anthony Brogan, Leo Brogan, David Brooks, Joan Ann Stephen Heery, Luke Heffernan, John Hehir, Barry O'Donoghue, Susan O'Donohoe, Joan O'Faherty,
Brosnan, Maurice Bryan, Daniel Buckley, Noel Henn, Joe Henry, Fergal Henry, Paul Higgins, Gerry Sean O'Farrell, John O'Flaherty, Eanna O'Flynn, Neil
Bugler, Patsy Burke, Eileen Burke, Paul Burke- Higgins, John Higgins, Iain Hill, Gary Hill, Kathleen O'Gorman, Maree O'Gorman, Rosemary O'Gorman,
Kennedy, Tim Burkitt, Roger Bushell, Marian Bushell, Hinde, Mike Hirst, Con Hogan, Dan Hogan, Sean Richard O'Gorman, Olivia O'Gorman, John O'Halloran,
Andrew Butler, Jim Byrne, Paul Byrne, Brian Caffrey, Hogan, Mick Hogan, Staphanie Holstead,Chris Honan, Donna O'Halloran, William O'Halloran, Tim O'Hara,
Sue Callaghan, Greg Campbell, Richard Cannon, John Joe Hopkins, Chris Houlihan, Mairin Hughes, Jackie Jane O'Hara, Michael O'Keefe, Daniel O'Keefe, Jean
Carey, Susan Carmody, Bruce Carrick, John Carroll, Hunt, Geoff Hunt, Trevor Hunter, Caroline Hurley, Ben O'Keefe, Ciaran O'Keeffe, Denis O'Mahony, Ciara
Terry Carruthers, Alison Carter, Edward Carty, Helen Huskinson, Trish Hyde, John Hynes,Robert Imbush, O'Mahony, Dermot O'Mahony, Elaine O'Malley, Nuala
Carty, Catherine Casey, Stephen Casey, Ciaran Casey, Brendan Ingoldsby, Justin Ivory, Gearoid Jackson, O'Malley, Stephen O'Malley, Niall O'Muiri, Charlie
May Cashman, Noel Cassidy, Caomhe Cawley, Pat Margaret Jackson, Jack James, Graham Johnston, O'Neill, Michelle O'Neill, Claire O'Nolan, Ger O'Regan,
Christie, Simon Clark, Damian Clarke, Amanda Clarke, Stefan Jones, James Kapalo, Padraig Kavanagh, Joe Michelle O'Regan, Niall O'Reilly, Patrick O'Shea,
Tom Clear, Conor Clenaghan, Gerry Clerkin, Cameron Kavanagh, Laura Kavanagh,Tom Kealy, Paula Kearney, Stephen O'Shea, Christian Osthoff, Oran O'Sullivan,
Clotworthy, Michael Cobley, Letizia Cocchiglia, David Paul Keating, Elaine Keegan, Karen Keegan, Padraig Paddy O'Sullivan, Michael O'Sullivan, Michael
Cole, Kyran Colgan, Kendrew Colhoun, Bríd Colhoun, Keirns, Niamh Kellaghan, Katherine Kelleher, Joe & O'Sullivan, Dennis O'Sullivan, John Palmer,John
Kevin Collins, Jane Coman, Padraig Comerford, Annette Kelly, Aidan G. Kelly,Sean Kelly, Kilian Kelly, Parkin, Jordan Patton, James Pembroke, Chris
Declan Coney, Elerina Conneelly, Naoimh Conneely, Caroline Kelly, Therese Kelly, John Kennedy, Henry Peppiatt, Ben Phalan, Peter Phillips, George Phipps,
Patrick Conneely, Dan Connell, Eoin Connelly, Kenny, Fridolin Kerr, Antoin Kiely, Michael Killeen, Daphne Pochin Mould, Claire Pollock, Brian Porter ,
Caroline Connolly, Alan Connolly, Maurice Connolly, James Kilroy, Austin Kinsella, Ken Kinsella, Nancy Gerry Power, Andrew Power, Frank Prendergast, Paula
Paddy Connors, Jimmy Conroy, Dick Coombes, Alison Klein, Peter Kysela, Andrew Lambe , Olivia Lardner, Prendergast, Robin Price, Bob Price-Adams, Vanessa
Cooper, Alex Copland, Ilse Corkery, William Jim Lawlor, Niall Leahy, Ruth-Ann Leak, Suzanne Price-Adams, Aileen Prole, Paul Proudfoot Michael
Cormacan, Sean Corry, Paudie Cosgrove, Joe Ledwith, Larry Lenehan, Noel Lenehan, Joe Lennon, Purser, Pat Pykett, Paddy Quinn, John Quinn, Jessica
Costelloe, John Coveney, Donal Coveney, Phil Cox, Lesley Lewis, Michael Lewis, Ita Logan, John Lovatt, Quinn, Noel Raftery, Christopher Ramsey, Ted
Peter Craven, Michael Creegan, Peter Crisp, John John Lusby, Rob Lynch, Annette Lynch, Aine Lynch, Rearden, Mark Reed, David Rees, Moya Reid, Brian
Cromie, Jerry Cronin, Ciaran Cronin, Christine Croton, Jen Lynch, Tom Lynch, Linda Lyne, Jerry Lyons, Liam Reidy, Michael Reilly, Peadar Reynolds Mary Riordan,
Olivia Crowe, Miriam Crowley, Sekeeta Crowley, Lysaght, Carmel Mackey, Kay Macklin, Coilin A. Robb, Tony Roche, Marie Rochford, Tim Roderick,
Seamus Cuddy, Teresa Culhane, Seamus Culhane, MacLochlainn, Emer Magee, Rosie Magee, John Ger Rogan, Brendan Rooney, Marie Rooney, Hugh
Denis Cullen, Majella Cullen, Tony Culley, Maura Maher, Mary Mahony, Seamus Mallon, Colm Malone, Rothwell, Stuart Roy, Denis Ryan, Michael Ryan,
Culligan, Sinead Cummins, Kieran Cunnane, Alice Malachy Mangan,Declan Manley, Ruth Mann, Wendy Pearse Ryan, Tom Ryan, Donal Scannell, Franz
Curran, Breda Curran, Donna Curtin, Ignatius Cusack, Martin, Breffni Martin, Paddy Martin Angela Mason, Scholand, Sol Schvartzman, Lorcan Scott, James
John Cusack, Barry Dalby, Gregory Daly, Clive Albert Mason Seamus Masterson John Matthews, Pat Scully, Eoin Scully, Catherine Seale, Joe Shannon, Neil
Darling, John Davis, Mike Davis, Michael Davis, Maxwell, John McAdam, Louise McAlavery, Kate Sharkey, Bob Sharpe, Jim Sheehan, Hugh Shepherd,
Mark Davis, Claire Deasy, John Deasy, Hugh Delaney, McAney, Deirdre McAvinchey, Fiona McAuliffe, Brigid Ralph Sheppard, Kathryn Sheridan Paddy Sheridan,
Eamonn Delaney, Pat Dempsey, Edward Denniston, McCabe Nicholas McCabe, Peter McCarron, Flor Caroline Shiel, Mark Shorten, Pat Smiddy, Sean Smith,
John Mark Dick, Ethna Diver ,Terry Doherty, Anita McCarthy, Kathleen McCormick, Mark McCorry, Larry Moray Souter, Andrew Speer, Sarah Stapleton, Robert
Donaghy, Joe Doolan, Eamonn Doran, Paul Dowding, McDaid, Lee McDaid, Michael McDonagh, Cathy S Steed, Ray Stephens, Michael Stinson Jane Stokes,
Pascal Dower, Margaret Doweth, Frank Doyle, Hazel McDonald, Rosemarie McDonald, Caroline McDonald, Bob Strickland, Philip Strickland, Wendy Stringer,
Doyle, Susan Doyle, Pauline Doyle, Gene Draper, Sinead McDonnell, Seamus McDonough, Steve Neil Stronach, Denis Strong, Clodagh Studdert, Dave
Nick Duff, Richard Duff, Brian Duffy, Dave Duggan, McEntegart, Paul McFadden, Ger McGann, John Suddaby, Eva Sweeney, Eugene Sweeney, Niamh
Graham Duncan, Kevin Dunleavy, Teresa Dunne, McGillicuddy, Seamus McGinty, Bernie McGrath, E Sweeney, Eoin Sweetman, Mary Talbot, Malcolm
Rosaline Dunphy, Pat Durkin, Mary Durkin, Tommy oin McGreal, Brendan McGuigan, Congella McGuire, Tanner, Tom Tarpey, Rebecca Teesdale, Marianne Ten
Durkin, Jamie Durrant, Kieran Dwane, Bridget Dwyer, Becky McIndoe, Barbara McInerney, David McKay, Cate-Whilde, Bryan Thompson, Kate Thompson, Roy
Richard Dwyer, Maurice Eakin, Richard Eakins, Andrew McKeever, Rodney McKenna, Elizabeth Thompson, Niall Tierney, David Tierney, David
Nathalie Eakins, Declan Egan, Fiona Egan, Martin McKenna, John McKenna, Hugh McLindon, Barry Toohey, Peter Towe, Yvonne Traynor, Maura Turner,
Egan, Pat Egan, Siobhan Egan, Ciaran Egan, McMahon, Frank McMahon, Jim McNally, Brian Frank Turpin, Aine Ui Dhubhshlaine, Julie Vangendt,
Andrew Ellard, Jamie Ellis, John Emmett, Liam McNamara, David McNamara, Roger McNaughton, Pat Vaughan, Bart Venneman, Yvette von Cramon,
English, Martin Enright, Seamus Enright, Norman Josephine McNern, Peter McQuillan, Berna Brendan Wall, Marita Wall, Eugene Wallace, Paul
Evans, Dave Fabby, Finbar Fagan, Peter Fagan, Liz McQuillan, Rosena McShane, Anna McWilliam, Donal Walsh, Alyn Walsh, Cathy Walsh, David Walsh, Philip
Fahey, Patrick Fanning, Frances Farrell, Fiona Farrell, McWeeney, John Meade, Stephen Meaney, Tony Mee, Walton, Graham Webb, Andrea Webb, Pádraig Webb,
Shane Farrell, Kristina Feeney, Rory Feeney, Seamus Allan Mee, Oscar Merne, Cian Merne, Brian Meskell, Gill Weyman, Bill Wheel, Rob Wheeldon, Gerry
Feeney, Caitriona Fenton, Fernando Fernandez, Eamon Meskill, Robbie Miller, Les Milne, John Milroy, Wheeler, Ricky Whelan, Janet Whelehan, Michael
Connor Finch, John Fingleton, Catherine Fingleton, Nicholas Mitchell, Richard Moles, Sandra Molloy, Whelan, Paul Whitelaw, Kevin Whyte, Tristam Whyte,
Des Finnamore, Triona Finnen, Cathy Fisher, Therese Martin Moloney, Daniel Moloney, Jason Monaghan, Gareth Williams, Ray Wills, Chris Wilson, Faith Wilson,
Fitzgerald, Mary Fitzgerald, David Fitzgerald, Billy Jim Moore, Mark Moore, Des Moore, Peadar Morgan, Fran Wolstenholme, Will Woodrow, Jerry Wray,
Fitzpatrick, Tom Flanagan, Noel Flanagan, Pat Tim Morgan, Megan Morris, Doreen Morrison, Bea Michael Wright, Mick Wright, Piotr Wrobel.
Flemming, Leonard Floyd, Ciara Flynn, Enda Flynn, Moya, Donal Mulcahy, Pat Mulhern, Michael Murphy,
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