Download WM0415 AnnexA Jay Conflicts

Reviews of selected wildlife conflicts
and their management
Annex A:
Impacts of jays on game
and other interests
A report to Defra
D. Parrott
10 December 2012
WM0415 Annex A Final Report
10 December 2012
IMPACTS OF JAYS ON GAME AND OTHER INTERESTS
Contents
Page
Executive summary ................................................................................................................................. 1
1. Introduction ........................................................................................................................................ 3
2.
Aim .................................................................................................................................................. 6
3.
Methods .......................................................................................................................................... 6
4.
Results ............................................................................................................................................. 7
4.1 Game birds .................................................................................................................................... 7
4.1.1 Stakeholder survey................................................................................................................. 7
4.1.2 Diet studies ............................................................................................................................ 8
4.1.3 Correlational studies .............................................................................................................. 8
4.1.4 Nest predation studies ........................................................................................................... 9
4.1.5 Predator removal experiments .............................................................................................. 9
4.1.6 Impacts on game birds ......................................................................................................... 10
4.2 Outdoor poultry .......................................................................................................................... 11
4.2.1 Empirical studies .................................................................................................................. 11
4.2.2 Reviews ................................................................................................................................ 12
4.2.3 Impact on poultry................................................................................................................. 12
4.3 Birds of conservation concern .................................................................................................... 12
4.3.1 Correlational studies ............................................................................................................ 13
4.3.2 Nest predation studies ......................................................................................................... 14
4.3.3 Reviews ................................................................................................................................ 16
4.3.4 Predator removal studies..................................................................................................... 17
4.3.5 Impact on birds of conservation concern ............................................................................ 18
5.
Conclusions ................................................................................................................................... 20
6.
References .................................................................................................................................... 24
7.
Appendix I ..................................................................................................................................... 27
WM0415 Annex A Final Report
10 December 2012
Executive summary
1. The jay is listed on General Licences issued under the Wildlife and Countryside Act
1981, permitting control to prevent serious damage or disease; to preserve public health
or public safety; and to conserve flora and fauna (including wild birds). The jay’s
presence on General Licences has been questioned and Natural England is planning to
consult on its inclusion in its forthcoming consultation on General Licences.
2. A requirement was identified, therefore, to review the existing evidence relating to the
impact of jays on relevant interests, including game, poultry and wild birds of
conservation interest, in order to help inform decisions arising from the consultation. A
desk-top review was undertaken to collate the available evidence for any impacts and
evaluate their effect on the relevant stakeholder interests.
3. The UK population of jays has been estimated at 160,000 territories; smaller than the
populations of the other two main corvid nest predators listed on General Licence –
magpie (650,000 territories) and carrion crow (790,000 territories).
4. Jays are predominantly birds of woodland where most nest predation by jays occurs;
although predation also occurs in farmland where fragmented woodland is interspersed
with agricultural land and in mature gardens.
5. For game birds a number of studies have shown that predator abundance was inversely
correlated with game bird abundance and that numbers of gamebirds increased following
the removal of avian and mammal predators. Studies, however, have tended to focus on
predators as a guild or group rather than as individual species. There are no known
studies that have investigated the effect of jay predation alone on game birds.
6. Jays are likely to contribute to the predation of the eggs of wild game birds that inhabit
areas of woodland and adjacent farmland. Any predation by jays, however, represents an
unknown component of overall predation.
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7. For poultry, there was no empirical evidence of predation by jays on eggs or chicks.
Problems with jays appeared to be limited to small back-garden poultry units rather than
large-scale commercial units.
8. For wild birds of conservation concern, a number of studies have implicated the jay as the
principal nest-predator for a number of passerine species, including some species on the
UK’s Red and BAP lists. The predation rate of jays has been shown to range from 0-36%
of all prey species study nests, and from 1-60% of all predation events.
9. Although some woodland passerine species suffer an apparently high nest predation
pressure, the relative importance of jay predation in declines in their breeding populations
remains unknown.
Numerous factors including changes in woodland habitat and
migratory pressures will interact with predation, with the relative importance of
individual factors as species-specific drivers of population declines unclear.
10. In summary, there was a paucity of empirical data on predation by jays on game bird and
poultry. Jay predation on woodland passerines was more documented but still relatively
lightly studied.
11. This lack of information prevented any quantitative assessment of the impacts and
relative importance of jay predation on any of the stakeholder interests.
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1. Introduction
The jay Garrulus glandarius is a member of the Corvidae, or crow family, that in the UK
(along with the jay) includes the crow Corvus corone, raven Corvus corax, rook Corvus
frugilegus, jackdaw Corvus monedula, magpie Pica pica and chough Pyrrhocorax
pyrrhocorax. Jays are found across most of the UK, except northern Scotland and inhabit
both deciduous and coniferous woodland, as well as parks and mature gardens.
The British Trust for Ornithology (BTO) shows that since the 1960s the UK jay population
has fluctuated with no long-term trend (http://www.bto.org/birdtrends2010/wcrjay.shtml)
(Figure 2.1). The population remained stable in the species' preferred Woodland habitat until
the late 1980s, after which the population began to decline. This decrease followed an earlier
decline on farmland Common Bird Census (CBC) plots (Gregory & Marchant 1995). Longterm trends are stable overall, and the CBC/Breeding Bird Index (BBS) index has recorded
some increase in the recent 14 year period (Figure 1.1). Population increases during this
recent period (1995-2009) have been far larger in Wales than in England overall (Risely et al.
2011) (Table 1.1). In England, however, there has been large regional variation in population
changes, from a 23% decrease in the West Midlands to a 58% increase in East of England.
Figure 1.1 BTO data on trends in the UK population of jay
(http://www.bto.org/birdtrends2010).
Table 1.1 Recent trends in jay populations (CBC/BBS 1995 to 2009).
UK
+16%*
England
+8% (-23*to +58* per region)
Wales
+48%*
Risely et al. (2011); BTO/JNCC/RSPB; * statistically significant change
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In comparison to the jay, the other two main corvid nest-predators the carrion crow and
magpie (both on General Licence) have larger UK populations (Table 1.2) and have shown
long-term increases in population size (Figure 1.2).
Table 1.2 Comparison of UK population sizes for jay, carrion crow and magpie. Values
indicate the number of territories in 2000 (1988–91 Atlas estimate updated using CBC/BBS
trend (http://www.bto.org/birdtrends2010).
Corvid Territories
crow
790,000
magpie
650,000
jay
160,000
UK population trend 1966-2009
steady increase; recent signs of stabilisation
steady increase to late ‘80s then stabilisation and minor decrease last 5 years
fluctuating, no long-term trend
Figure 1.2 BTO data on trends in the UK populations of carrion crow and magpie
(http://www.bto.org/birdtrends2010).
Over the latter period 1995-2009 the UK crow population has shown a significant increase,
whilst magpies have shown a minor decrease. Again similar to jays there has been large
regional variation for both species (Table 1.3).
Table 1.3 Recent trends in UK populations of carrion crow and magpie (CBC/BBS 1995 to
2009).
Corvid
UK
England
Wales
crow
+9%*
+17%* (-0% to +80%* per region)
+1%
magpie
-3%
-3% (-27%* to +24%* per region)
-10%
jay
+16%*
+8% (-23*to +58* per region)
+48%*
Risely et al. (2011); BTO/JNCC/RSPB; * statistically significant change
The natural diet of many corvid species (including the jay) is omnivorous, consisting of
invertebrates (including insects, molluscs, earthworms and spiders), birds eggs and nestlings,
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small mammals, berries, fruits, seeds, cereals and other crops and carrion (e.g. Cramp and
Perrins 1994). Items listed as having appeared in the diet include adults, nestlings and eggs
of many birds, the great majority songbirds but including eggs and nestlings of Phasianidae
(includes pheasants and partridges). Uniquely amongst the corvids, the jay’s staple diet for
much of the year is acorns Quercus sp. (Goodwin 1955; Holyoak 1968), with most of those
eaten during the spring and summer having been cached during the previous autumn and
winter (Goodwin 1955; Holyoak 1968).
The propensity of corvids to take the eggs and nestlings of other birds has brought them into
conflict with a number of stakeholder interests; principally the game bird industry but there
are also concerns associated with free-range poultry and wild birds of conservation concern.
General licence
The jay is listed on the General Licence issued under the Wildlife and Countryside Act 1981,
permitting control to prevent serious damage or disease, to preserve public health or public
safety, and to conserve flora and fauna (including wild birds) (Table 1.4). Its presence on the
General Licence has been questioned and Natural England is planning to consult on its
inclusion in its forthcoming consultation on General Licences. The existing evidence relating
to its impact on relevant interests, including on game, livestock, poultry and wild birds of
conservation concern thus needs to be reviewed to help inform decisions made as a result of
the consultation.
General licences are issued by government agencies to provide a legal basis for people to
carry out a range of activities relating to wildlife. In England (licensing authority Natural
England), the jay (and 13 other species) are listed on one or more general licences for
preventing serious damage (e.g. to livestock and crops) and preventing the spread of disease
(WML-GL04), to preserve public health or safety (WML-GL05) and to conserve flora and
fauna (WML-GL06) (Table 1.2). These licenses permit landowners, occupiers and other
authorised persons to carry out a range of otherwise prohibited activities against the species
of wild birds listed on the licence. Control methods allowed may include shooting, the
destruction of eggs and nests, and the use of Larsen traps and multi-catch traps.
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Table 1.4 Avian species listed on Natural England General Licences.
Species
Crow
Collared dove
Lesser black-backed gull
Herring gull
Jackdaw
Jay
Magpie
Feral pigeon
Rook
Woodpigeon
Canada goose
Egyptian goose
Monk parakeet
Ring-necked parakeet
Corvus corone
Streptopelia decaocto
Larus fuscus
Larus argentatus
Jackdaw
Garrulus glandarius
Pica pica
Columba livia
Corvus frugilegus
Columba palumbus
Branta canadensis
Alopochen aegyptiacus
Myiopsitta monachus
Psittacula krameri
WMLGL04a
X
X
X
X
X
X
X
X
X
X
X
X
WLMGL05b
X
X
X
X
X
X
X
X
X
X
X
X
WLMGL06c
X
X
X
X
X
X
X
X
X
X
X
a
WML-GL04: To kill or take certain wild birds to prevent serious damage or disease.
WML-GL05: To kill or take certain birds to preserve public health or public safety.
c
WML-GL06: To kill or take birds to conserve flora and fauna (including wild birds).
b
2. Aim
The aim of the study was to undertake a desk review of the conflicts between jays and game,
poultry and wild birds of conservation interest. Specific objectives were to collate the
available evidence for any impacts and evaluate their effect on the relevant stakeholder
interests (drawing on evidence from the UK and Europe).
3. Methods
The initial approach involved the collation and evaluation of the available published scientific
literature. This was achieved by searching standard reference and citation databases using
Fera’s state of the art information centre facilities. Relevant material was identified and
obtained and further references that were present in the material were then sourced. The
authors of this material were also used as search terms to search for grey literature and
potential further data sources. Where appropriate the authors of such material were contacted
to determine whether information on as yet unpublished studies might be made available for
incorporation into the review. As well as contacting authors of grey literature, Fera also
contacted key scientists and organisations (both government and NGO) associated with the
stakeholder interests in order to identify other potential sources of relevant information.
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All relevant references and data sourced were reviewed and information extracted (as far as
possible) in relation to the setting, nature, timing, extent and magnitude of any impact.
The review revealed, however, a general paucity of information on jay interactions with the
majority of the stakeholder interests, in particular game and poultry. The current review,
therefore, encompasses qualitative descriptions of jay associations with game and poultry,
with the available empirical data limited to relationships between jays and wild birds.
4. Results
4.1 Game birds
Information sources that provided evidence for the presence of predators and/or their impacts
on game birds included: (i) stakeholder surveys, (ii) diet studies, (iii) nest predation studies,
(iv) correlational studies and (v) predator removal experiments. The major limitation with
much of this data was that the studies often did not distinguish between the effects of
individual predator species. Generally, the studies focus on groups of species, which may
include all ‘predators’ (which can comprise both avian and mammal predators), or smaller
groupings, such as ‘corvids’. In these studies, therefore, any effect of jays could not be
separated from that of other predators.
4.1.1 Stakeholder survey
In February 2011, the National Gamekeepers’ Organisation (NGO) and the Scottish
Gamekeepers’ Association (SGA) commissioned a questionnaire survey to assess the quarry,
predator
and
wildlife
species
found
on
shooting
estates
throughout
the
UK
(http://www.nationalgamekeepers.org.uk/library/resource/132/. Returns were received from
941 gamekeepers (from 5,500 contacted) that were still involved in managing a shoot. Of
these, 823 (87.5%) reported the presence of jays, with 653 (79.3% where jays were present)
of these controlling them. No evaluation was presented on the relative impacts (perceived or
measured) of individual predator species.
Jays are listed amongst the potential predators of red grouse Lagopus lagopus nest contents
by
the
North
York
Moors
National
Park
(http://www.nationalparks.gov.uk/grouse_shooting_in_the_north_york_moors.pdf).
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Authority
4.1.2 Diet studies
Holyoak (1968) summarised the results of the analyses of gizzards from British corvids,
focussing on carrion crow, rook, jackdaw, magpie and jay. The birds originated from a
number of localities in lowland England and Wales, all in farming areas. For jays, 74
gizzards were examined. The most important food items for jays were acorns and beechmast,
woodland insects ‘passerine birds’ eggs’ and ‘passerine pulli’. Of 19 gizzards originating
from birds killed in March and April, 11% contained passerine eggs. Of 25 gizzards from
birds killed in May-June, 8% contained eggs and 8% contained pulli. The eggs of game birds
or livestock were not listed amongst the diet of jays, whereas ‘game bird eggs’ was listed for
magpies and ‘hen and duck eggs’ for carrion crow.
4.1.3 Correlational studies
A number of studies have investigated relationships between the relative abundance of
predators and the numbers of game birds or game bird breeding performance (e.g. nest
predation rate). In such an approach, if the data indicates that numbers of predators are
negatively correlated with prey numbers or performance it lends support to the hypothesis
that predators have caused the trend. However, it is not possible to demonstrate cause and
effect from correlational studies, prey numbers or breeding performance may be associated
with predator density, but this link can only be assumed and is not proven.
There are a number of problems with the interpretation of observations from correlational
studies. A negative relationship between predator and prey densities may have an alternative
explanation. For example, predators and prey may have different habitat requirements, so
that they tend to be relatively more abundant in different parts of the study area. In Britain,
differences in breeding densities and breeding success of black grouse Tetrao tetrix have
been related to the intensity of grazing on moorland and not solely predator management
(Baines 1996). Within years, densities and breeding success were higher on lightly grazed
moors, compared to those heavily grazed, irrespective of the presence of a gamekeeper.
Where the mechanism underpinning any effect of a treatment is complex, for example where
mesopredator release may lead to increases in smaller predators, then correlational studies
will be limited in their ability to understand or interpret the effects of any treatment.
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For corvids, in Sweden, across three study areas the rate of predation on artificial grouse
nests increased with increasing density of corvids (unspecified species) (Andren et al. 1985).
However, although earlier work had shown that corvids appeared to be the main predators of
artificial tetraonid (i.e. grouse, partridge, quail) nests the study did not present data on the
relative predation rates between corvids and other predators. Both the loss rate of artificial
nests and corvid density were positively related to the proportion of agricultural land and to
the degree of fragmentation of forest habitats.
Correlational studies involving corvid abundance have tended to focus on corvids as a group
rather than as individual species.
Any correlation between the abundance of jays and
predation rates on game bird nests, therefore, will have represented an unknown component
of the corresponding overall association with corvid abundance.
4.1.4 Nest predation studies
The fate of nests of radio-tagged hen pheasants were analysed from six sites between 1990
and 2003; the sites were located in East Anglia, Wiltshire, Dorset and Lower Austria
(Draycott et al. 2008).
Predation accounted for the failure of 43% of nests (n=444).
Characteristic field signs were used to identify the predators responsible. Of 191 predated
nests, corvid and fox were the most common predator taking 24% and 23% of nests
respectively (a further 31 nests failed due to foxes taking nesting hens while away from the
nest); in 33% of cases the identity of the nest predator could not be confirmed. There was no
data, however, on the relative predation rates of individual corvid species, including jay.
4.1.5 Predator removal experiments
Any effect of predators limiting their prey can be shown most convincingly by experiment,
such that removal of predators should be followed by an increase in prey numbers (Newton
1998).
Predator removal experiments fall into three design categories: (i) paired-site
experiments, (ii) cross-over experiments and (iii) before-and-after experiments.
Reviews of predator removal experiments (Cote & Sutherland 1997; Newton 1998;
Nordstrom 2003; Gibbons et al. 2007; Smith et al. 2010) indicate that in the majority of
studies removal of predators resulted in an increase in one or more breeding parameters of
birds, i.e. nesting success, post-breeding numbers or breeding numbers. However, although
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removal of predators often increases numbers of prey alive at the end of the breeding season,
different reviews drew different conclusions as to whether there is a consistent increase in
numbers of breeders in subsequent years.
The impact of predators (and the effects of their removal) has also been shown to be context
specific. The effects of a reduction in predation pressure interacting with other factors
affecting bird productivity and survival, such as land management and environmental
stressors (e.g. temperature, rainfall) (Evans 2004).
Jays are likely to contribute to the predation of the eggs of wild game birds that inhabit areas
of woodland and adjacent farmland, albeit to some unknown extent. There are no known
predator removal experiments that have investigated the effect of the removal of jays alone
on game bird nesting success.
4.1.6 Impacts on game birds
Data on the extent and magnitude of jay nest predation on game birds was not available.
Studies have tended to focus on predators as a group (e.g. corvids or all predators) rather than
as individual species. Any predation by jays, therefore, represents an unknown component of
overall predation by corvids or all predators.
In terms of the relative UK abundance of the three main corvid nest-predators, jays are less
numerous than carrion crows and magpies (see section 2). Also, in terms of long-term trends
(1966-2009), the UK populations of carrion crow and magpie have increased whilst the jay
has fluctuated with no long-term trend.
Jays are primarily found in woodland and prey on nests within woods or on woodland edges
(Moller 1989; Andren 1992) and have been recognised as important predators of the nests of
a number of species of woodland birds (Fuller et al. 2005; Stevens et al. 2007, 2008;
Weidinger 2009). Jays however, can also predate nests in farmland and gardens (Stevens
2008).
In a study of radio-tagged hen pheasants, 43% of nests were in woodland, 30% in arable
fields, 13% in field margins, 7% in set-aside, 6% in grassland and 1% in other habitat types
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(Draycott et al. 2008). Therefore, around 43% of pheasant nests were in habitat that placed
them at the greatest potential risk of predation by jays. In Draycott et al.’s (2008) study, 51%
(n=159) of pheasant nests in woodland were predated (in comparison 40-52% were predated
in other habitats). Elsewhere in Draycott et al. (2008) 24% of 191 predated nests were
attributed to corvids, across all habitats (the rate of corvid predation on nests in woodland
was not presented).
Grey and red-legged partridges locate their nests along field boundaries and on rough ground
rather than in woodland (Rands 1988). As described by the GWCT (2009) nest sites tend to
be on free-draining soil on a slope preferably facing south and with shelter from the
prevailing wet weather. Nests are a shallow scrape concealed in dense vegetation such as
rank tussocky grass, herbaceous perennials and the crops themselves. As a consequence
partridge nests are likely to be at less risk of predation by jays compared to pheasant nests.
Although a proportion of game bird nests are potentially at risk from predation by jays, in the
absence of the relevant empirical studies it is not possible to attempt an evaluation of the
extent and magnitude of predation, or its relative importance in comparison to predation by
other predators, including other corvids.
4.2 Outdoor poultry
Poultry units can range from free range smallholdings containing just one or two birds
through to enclosed battery farms and broiler houses containing many thousands of birds
(Defra 2006; BBC 2007). Units may be utilised for hatcheries, meat or egg production, or a
combination of the three. Sites may offer a variety of attractions to different wild bird
species. This could include opportunities for scavenging or predating food in the form of
poultry feed, insects, rodents, eggs, chicks and potentially adult birds.
4.2.1 Empirical studies
In France, a field study to quantify the overall levels of free-range poultry (producer flocks)
losses to predators and to identify which species were involved in depredation did not record
the jay amongst the list of predators that took chickens aged five weeks and above (chickens
began to leave the hen house at five weeks of age) (Stahl et al. 2002). In 276 depredation
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events, 52% were caused by avian predators with crows attributed to 9% of events and 4% of
chickens killed.
4.2.2 Reviews
Baxter et al. (2007) (Appendix 2 Defra Project SE4206) reviewed the available published
literature to identify knowledge that could be used to assist with modelling the potential
spread of Avian Influenza (AI) by UK birds. As part of this review, corvids were identified
as species utilising outdoor poultry units. Ravens have been reported scavenging chicken
waste, crows depredating young chickens, ducklings and eggs, rooks depredating ducklings,
and magpies taking eggs and hatchlings. In contrast, however, the review found no reference
in the literature to jays being present at or using poultry farms.
At small back-garden poultry units, however, there are a number of anecdotal reports on the
internet of jays predating eggs; including eggs laid in the garden and in nest boxes
(www.thepoultrykeeper.co.uk; www.thepoultrygarden.com).
4.2.3 Impact on poultry
For poultry, there were no empirical estimates of predation by jays on eggs or chicks.
Problems with jays appeared to be limited to small back-garden poultry units rather than
large-scale commercial units.
4.3 Birds of conservation concern
In the case of wild birds, predation is a major cause of nest failure (Ricklefs 1969; O’Connor
1991; Martin 1993) and may be an important factor influencing the composition and
conservation of avian communities (Newton 1998).
Evidence for the role of jays in the nest-predation of passerines has been investigated using:
(i) correlational studies, and (ii) direct observation of predation events.
In addition to nest predation, jays have also been recorded killing adult passerines (e.g. house
sparrow) and taking newly fledged young outside the nest (reviewed in Cramp and Perrins
1994).
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4.3.1 Correlational studies
A number of correlational studies have involved the use of long-term national bird survey
datasets, investigating, for example, whether spatial or temporal change in prey abundance is
inversely related to changes in predator abundance.

Paradis et al. (2000) studied large-scale spatial variation (10-km squares) in
reproductive output of two declining species, the song thrush Turdus philomelos and the
blackbird Turdus merula. The study utilised the British Trust for Ornithology’s (BTO) Nest
Records Scheme and related environmental variables to reproductive output; the
environmental variables included the combined frequencies of occurrence of the corvids
magpies and jays. Nest failure rate during incubation increased significantly where corvids
were most abundant. There was no evidence however, that high failure rates were actually
caused by jays and/or magpies (or the relative involvement of each species) as data on the
identity of nest predators was unavailable.

Siriwardena (2004) analysed the BTO’s long-term national datasets on bird abundance
(Common Bird Census) and annual capture frequencies from the Constant Effort Sites (CES)
ringing scheme to investigate potential causes for the population decline of the British willow
tit Parus montanus population. There was no evidence for any negative correlation with the
abundance of any predator (including jay), other than with great spotted woodpecker
Denrocopus major on farmland.

Newson et al. (2010) applied novel analytical methods to national bird datasets
(BTO/JNCC/RSPB Breeding Bird Survey and BTO/JNCC Common Birds Census) to
examine whether the populations of 29 English birds may have been depressed by increases
in abundance of two broad categories of predators.
The two categories comprised: (i)
sparrowhawk Accipiter nisus, kestrel Falco tinunculus and buzzard Buteo buteo (predators of
juvenile and adult birds), and (ii) carrion crow, black-billed magpie, jay, great spotted
woodpecker and grey squirrel Sciurus carolinensis (predators of nests). For 22 of the prey
species there was no statistical evidence that increases in common avian predators in recent
years have resulted in population declines. Further, prey species with declining populations
were no more likely to be negatively associated with an increase in predators than prey
species with stable or increasing populations.
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For corvids, including jays, there were no statistically significant negative
associations with any prey species; in fact there were a large number of positive associations.
Overall, Newson et al.’s (2010) analysis provided little underlying evidence for largescale impacts of widespread avian predators on avian prey populations. It could not be
excluded, however, that the small number of negative associations between particular
predator and prey species reflect causal relationships or impacts at smaller spatial scales.
4.3.2 Nest predation studies
Advances in digital camera/video technology have made studies on the direct observation of
nest-predation increasingly practical.
This approach allows both the identification of
individual predator species and their relative contribution to the overall rate of nest-predation.
Nest predation studies have used both natural and artificial nests.
Natural nests
A number of nest-predation studies have revealed jays to be involved in the predation of the
nests of passerine species.

Schaefer (2004) used video-recording to investigate the predation on natural blackcap
Sylvia atricapilla nests in Germany. The main predator was the jay, which took eggs or
young from 21% of all nests monitored (n=126) and represented 60% of all nest predation
events (n=40).

Remote monitoring using digital cameras was used to record predation events at the
nests of ground-nesting lapwings Vanellus vanellus (40 nests in North Wales) and treenesting spotted flycatchers Musicapa striata (17 nests in south Devon) (Bolton et al. 2007).
For lapwings four predators were recorded taking eggs at 10 nests: fox Vulpes vulpes (6
nests), badger Meles meles (2 nests), carrion crow (1 nest) and sheep Ovis aries (1 nest). For
spotted flycatcher, four predators were recorded at 7 nests: Jays (four nests), buzzard (1 nest),
great spotted woodpecker (1 nest) and domestic cat Felis catus (1 nest). Jays, therefore, were
the main predator of spotted flycatcher nests, responsible for predating 24% of all spotted
flycatcher nests (n=17) and 57% of all predation events (n=7).
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
Predation on natural spotted flycatcher nests was investigated in three habitats
(woodland, farmland, gardens) in two study areas (Devon and Bedfordshire/Cambridgeshire)
in England (Stevens et al. 2007, 2008). Nests in gardens were more successful than those in
farmland and woodland (at both egg and chick stages) (Stevens et al. 2007). Estimates of
productivity per nesting attempt were also lower in farmland and woodland than in gardens.
The most frequent cause of nest failure was predation.
The identity of predators was
investigated using remote digital nest-cameras (Stevens et al. 2008). The exact fate of eggs
and nestlings was determined for 63 of the 65 nests monitored by camera. The jay was the
main nest predator, responsible for predating 12 nests representing 19% of all nests (n = 63)
and 60% of all predation events (n = 20). Other predators were domestic cat (3 nests), great
spotted woodpecker (2 nests), buzzard (1 nest) sparrowhawk (1 nest) and jackdaw (1 nest).
Predation rates by jays varied between different habitats: woodland (42-47%) > farmland (1416%) > gardens (4%).

Jays and buzzards were recorded predating open songbird nests in fragmented
deciduous woodland in the Czech Republic (Weidinger 2009). Over a five year period, a
total of 178 predation events at 168 nests were videotaped. Jay and buzzard were responsible
for 29% (52 events) and 7% (13 events) of these predation events, respectively. Species
depredated by jays were: blackcap (40% of all depredated nests), song thrush (15%),
blackbird (14%), yellowhammer Emberiza citrinella (56%), chaffinch Fringilla coelebs
(37%), chiffchaff Phylloscopus collybita (7%), dunnock Prunella modularis (38%). The jay
was the main predator of blackcap, yellowhammer and chaffinch.
Artificial nests
Many studies that have investigated nest predation have used artificial nests (Angelstam
1986) or artificial eggs within real nests (Remes 2005). Results from such studies have been
used to infer how a range of ecological and anthropogenic factors are likely to influence
avian populations. Reviews of artificial nest studies, however, have shown that predation of
artificial nests is a weak indicator of predation of real nests (Major & Kendal 1996; Moore &
Robinson 2004). Therefore, care must be taken in extrapolating findings to natural nest sites.

The identity of the predators of ground-nesting birds was investigated in a
farmland/forest mosaic in Sweden (Angelstam 1986). Artificial nests that recorded the foot15
WM0415 Annex A Final Report
10 December 2012
prints of predators allowed the identification of the predator in 76 events. The main predator
was the jay and was responsible for 47% of predation events.

In Denmark, Moller (1989) investigated nest predation by corvids (hooded crow
corvus cornix, magpie and jay) on open and closed artificial nests relative to distance from a
field-woodland ecotone (boundary). Nest predation intensity for each corvid species was
proportional to their local abundance; jays were primarily found in woodland. The different
corvid species preyed on nests at different distances from the field-woodland boundary; jay
preyed primarily on nests within the woodland – 93% of predated nests were within or on the
woodland edge.

In Sweden, Andren (1992) investigated the abundance and distribution of corvids and
predation rates on dummy nests, in relation to forest fragmentation, in a series of 4km2 study
plots across a landscape gradient from an agricultural land dominated landscape to a forest
dominated landscape.
Jays were absent from small forest fragments in a matrix of
agricultural land and mainly preyed upon dummy nests inside the large forest fragments.
Predation in forests accounted for 10% of all nests (n=258) and 12% of all predation events.
The jay predated less nests than all other corvids studied (hooded crow, jackdaw/magpie and
raven).
4.3.3 Reviews
A number of studies have reviewed the evidence for the role of predation on wild birds and
on declining species in particular. There is, however, very limited reference specifically to
jays in these reviews.

Newton (1993) stated that of the species that have been studied those who’s breeding
numbers appear most likely to be depressed by predators are ground-nesting game birds and
waterfowl.

Cote and Sutherland (1997) in a review of 110 studies of nest predation concluded
that ground-nesting species were not more susceptible to nest predation than species nesting
off the ground in open or closed nests; although cavity nesters experienced significantly
lower predation than species using any other nest type.
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WM0415 Annex A Final Report
10 December 2012

Fuller et al. (2005) examined possible causes for the large declines in breeding
populations and breeding range of several woodland birds in Britain. Jays were recognised as
especially important predators of birds’ nests but there was little evidence for a long-term
increase in jay populations in Britain. More generally little evidence was found of clear links
between numbers of woodland songbirds and the abundance of avian predators. It was
recognised, however, that predation could have an important secondary effect when
populations are already under pressure from other factors.

Gibbons et al. (2007) reviewed the conservation impact and management of predation
on wild birds in the UK. The review drew a number of conclusions: (i) the populations of
many UK predators have increased in recent decades, (ii) there is growing evidence that for
some ground-nesting birds breeding populations are limited by predation, and (iii) in contrast,
there is little evidence that songbird numbers are limited by predation.

As part of the government’s Natural Environment Public Service Agreement to
safeguard, value and enhance biodiversity, an indicator of wild birds has been adopted. This
indicator comprises an aggregate of sub-indices for breeding farmland, woodland and
wetland birds.
The woodland indicator includes 35 species, 19 of which are showing
population trends below the baseline year estimate. For 18 of these species (considered to be
priorities) (including nine BAP species) Charman et al. (2009) reviewed the evidence base
for the causes of declining populations in England. The review recognised that the problem
of declining populations is multi-factorial and that establishing the relative importance of
species-specific drivers of decline is extremely difficult. Although predation is recognised as
a common cause of nest failure there is little evidence that songbird numbers are limited by
predation.
4.3.4 Predator removal studies
Predator removal studies that have investigated the effect of corvid removal on passerines
have focussed either on corvids as a group, or on species other than jay, e.g. crow and
magpie. Different studies have shown contrasting effects associated with corvid removal.
For example:
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WM0415 Annex A Final Report
10 December 2012

Stoate and Szczur (2001) monitored changes in numbers of passerines over six years
in a 200km2 area of mixed arable and livestock farms in Leicestershire.
The area
encompassed arable fields, grassland, hedges and numerous small woods. The abundance of
nationally declining breeding passerines increased during periods when crows and magpies
were removed as part of wider game management practices. The precise mechanism by
which the game management package contributed to increased breeding numbers is not
understood.

Chiron and Julliard (2007) tested the role of magpies in the limitation in post-
fledgling and adult numbers of ten common songbird species, in suburbs near Paris, France,
using a controlled, replicated trial. Magpies had very limited effect on songbird productivity.

Using meta-analysis to summarise results from 83 predator removal studies, Smith et
al. (2010) concluded that removing predators increased hatching success, fledgling success
and breeding populations. The study did not investigate predator taxa.
4.3.5 Impact on birds of conservation concern
A number of empirical studies utilising digital cameras at nests have shown some passerine
species to suffer high rates of nest predation with the jay as the main predator (Bolton et al.
2007; Stevens et al. 2008; Weidinger 2009). The predation rate of jays has been shown to
range from 0-36% of all nests within a study (all prey species), and to account for 1-60% of
all predation events recorded (Table 4.1).
The list of species whose nests jays predate include a number of species that are on the UK
Red List and UK BAP list – song thrush, yellowhammer and spotted flycatcher (Table 4.2).
Although jays can exert a high predation pressure on some passerines, how this may translate
into a population level effect is not clear (Charman et al. 2009). High levels of predation in
themselves are not sufficient to demonstrate that predation is driving declines in prey species
populations, or causing populations to be sustained at low levels. Jays (or other predators)
may be taking similar numbers of eggs and nestlings that may have died anyway from other
causes (Gibbons et al. 2007).
Predation should be considered a contributory driver to
population declines but not at the exclusion of other factors (Charman et al. 2009) and may
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WM0415 Annex A Final Report
10 December 2012
represent an important secondary effect when populations are already under pressure from
other factors (Fuller et al. 2005). Amar et al. (2006), reporting an investigation into changes
in breeding populations of woodland birds, concluded that a range factors may operate in a
species- and/or region-specific manner, and that interactions between factors may be critical.
Evans (2004) reviewed the mechanisms through which habitat change and predation could
interact and how these may have contributed to population declines of farmland birds.
Examples of interaction mechanisms mediated through habitat change include increased
densities of predator or prey leading to increased encounter rates and increased nest predation
rates due to increased nest visibility.
In the case of the spotted flycatcher, Charman et al. (2009) considered that there was slightly
stronger evidence that predation may be an important driver of recent population declines in
some areas. The species suffers a high rate of nest predation with the jay the principal
predator (Schaefer 2004; Stevens et al; 2008, Weidinger 2009). The Breeding Bird Survey
records declines of 47% in the UK and 52% in England during 1995-2009 (Risely et al.
2011). The BBS, however, is a national monitoring scheme which is based on data from all
habitats in which species are recorded, rather than from the species preferred habitat, which
in the case of spotted flycatcher (and jay) is woodland. Population trends from BBS (and
other similar national surveys) may therefore not be representative of changes to populations
in woodland per se.
The Repeat Woodland Bird Survey (RWBS), however, which investigated trends in breeding
bird populations in British broadleaved and mixed woods between the mid-1980s and 200304, reported comparable large declines of spotted flycatchers - 70% decrease in territories per
hectare and 36% decrease in the number of birds recorded per survey point (Amar et al.
2006). Population modelling suggested that the decline may have been driven by a decrease
in the annual survival rate of fledged birds, either shortly after fledging or within the
subsequent first year of life (Freeman and Crick 2003). Jays are known to take newlyfledged young. In one long-term study in Germany, jays were said to take up to 85% of
newly-fledged young (Henze 1979 cited in Cramp and Perrins 1994).
Despite evidence that the jay is the primary nest-predator of spotted flycatchers there appears
to be no clear association between the abundance of jays and numbers of spotted flycatchers
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WM0415 Annex A Final Report
10 December 2012
in the UK. There has been regional variation in changes in jay populations across the UK.
Between the mid-1980s and 2003-04 declines were detected in all English regions except the
north (i.e. North West, North East and Scotland) (Amar et al. 2006). In the more recent
period 1995-2009, there have been regional increases in the North West and East England
(Risely et al. 2011). For spotted flycatcher the RWBS confirmed large declines in woodland
in most regions (Amar et al. 2006). Fuller et al. (2005) suggested that declines of spotted
flycatcher may be due to pressures during migration or on the wintering ground. The large
population increase in the South West (though the BBS records a regional decrease for the
period 1995-2009; Risely et al. 2011), however, suggests that factors in the breeding grounds
may also be involved (Amar et al. 2011). Declines in populations have occurred for all longdistance migrants (Amar et al. 2011).
5. Conclusions
There was a paucity of information on predation by jays on game bird and poultry. Jay
predation on woodland passerines was more documented but still relatively lightly studied.
This lack of information prevented any quantitative assessment of the impacts of jays on any
of the stakeholder interests.
For game birds, jays are likely to predate nests of wild populations, such as pheasants, with
this concentrated on those nests within or on the edges of woodland. The relative occurrence
of jay predation on the nests of game birds and its potential significance is unknown.
For poultry, problems with jays appeared to be limited to small back-garden poultry units
rather than large-scale commercial units.
In order to provide robust estimates of the potential impacts of jays on game and poultry the
appropriate studies would need to be undertaken to provide the required data on which such
estimates would be based.
For wild birds of conservation concern, a number of studies have implicated the jay as the
principal nest-predator for a number of UK red and BAP list passerine species. The predation
rate of jays has been shown to range from 0-36% of all prey species study nests, and from 120
WM0415 Annex A Final Report
10 December 2012
60% of all predation events. Although some passerine species suffer an apparently high nest
predation pressure, the relative importance of any effect of jay predation in declines in the
breeding populations remains unknown. Numerous factors including changes in woodland
habitat and migratory pressures will interact with predation, with the relative importance of
individual factors as species-specific drivers of population declines unclear.
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WM0415 Annex A Final Report
10 December 2012
Table 4.1 Summary of studies that have measured predation rates by jays using remote monitoring.
Predation rates by jays relative to all study nests
Study
Country
Type
Nests
Video-monitoring
Nest cameras
Digital nest cameras
Digital nest cameras
Track plates
Track plates
Germany
UK
UK
UK
Sweden
Sweden
Natural
Natural
Natural
Natural
Artificial
Artificial
126
63
17
40
101
181-258c
Jay
(n)
24
12
4
0
36b
28c
Jay
(%)
19
19
24
0
36b
1-10c
Predator
Rank
1st
1st
1st
NA
1st
4th (of 6)
Prey speciesa
BC
SF
SF
L
Dummy ground-nesters
Dummy prey
Eggs Nest
Y
Y
Y
y
Y
Y
?
N
NA
NA
Reference
Schaefer 2004
Stevens et al. 2008
Bolton et al. 2007
Bolton et al. 2007
Angelstam 1986
Andren 1992
a
BC = blackcap Sylvia atricapilla; ST = song thrush Turdus philomelos; B = blackbird Turdus merula; Y = yellowhammer Emberiza citrinella; CH = chaffinch Fringilla
coelebs; CC = chiffchaff Phylloscopus collybita; DN = dunnock Prunella modularis; SF = spotted flycatcher Muscicapa striata; L = lapwing Vanellus vanellus.
b
minimum number of all nests (n=150) predated by jay as at some nests the predator was unidentified.
c
varied by habitat: forest (n=258) = 26 nests (10%), agricultural land (n=181) = 2 nests (1%).
Predation rates by jays relative to all predated nests (all predators)
Study
Country
Type
Events
Jay
Jay
(n)
(%)
Time-lapse video
Czech Rep.
Natural
178
52
29
Predator
Rank
2nd
Time-lapse video
Video-monitoring
Nest cameras
Digital nest cameras
Track plates
Track plates
1st
1st
1st
1st
1st
4th (of 6)
d
Czech Rep.
Germany
UK
UK
Sweden
Sweden
Natural
Natural
Natural
Natural
Artificial
Artificial
55
40
20
7
76
176-218d
22
24
12
4
36
28d
40
60
60
57
47
1-12 d
varied by habitat: forest (n=218) = 26 nests (12%), agricultural land (n=176) = 2 nests (1%).
22
WM0415 Annex A Final Report
10 December 2012
Prey species
BC (22), ST (5), B (4), Y
(9), CH (8), CC (1), DN (3)
BC
BC
SF
SF
Dummy ground-nesters
Dummy prey
Eggs Nest
Reference
25
27
Weidinger 2009
Y
Y
y
Y
Y
?
NA
NA
Weidinger 2009
Schaefer 2004
Stevens et al. 2008
Bolton et al. 2007
Angelstam 1986
Andren 1992
Table 4.2 Summary of avian species predated by jays (from remote monitoring studies) and their conservation status.
Species
song thrush
Turdus philomelos
yellowhammer
Emberiza citrinella
spotted flycatcher
Muscicapa striata
dunnock
Prunella modularis
black cap
Sylvia atricapilla;
blackbird
Turdus merula
chaffinch
Fringilla coelebs
chiffchaff
Phylloscopus collybita
Status
Red List
Red List
Red List
Amber List
Green List
Green List
Green List
Green List
UK BAP species
Yes
Yes
Yes
No
No
No
No
No
See appendix I for red/amber/green listing criteria
23
WM0415 Annex A Final Report
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Reference
Weidinger 2009
Weidinger 2009
Bolton et al. 2007; Stevens et al. 2008
Weidinger 2009
Schaefer 2004; Weidinger 2009
Weidinger 2009
Weidinger 2009
Weidinger 2009
6. References
Amar A, Hewson CM, Thewlis RM, Smith KW, Fuller RJ, Lindsell JA, Conway G, Butler S,
MacDonald MA. 2006. What’s happening to our woodland birds? Long-term changes in
the populations of woodland birds. RSPB Research Report no. 19 and BTO Research
Report no. 169.
Andren H. 1992. Corvid density and nest predation in relation to forest fragmentation: a
landscape perspective. Ecology 73(3): 794-804.
Andren H, Angelstam P, Lindstrom E, Widen P. 1985. Differences in predation pressure in
relation to habitat fragmentation: an experiment. Oikos 45: 273-277.
Angelstam P. 1986. Predation on ground-nesting birds’ nests in relation to predator densities
and habitat edge. Oikos 47: 365-373.
Baines D. 1996. The implications of grazing and predator management on the habitats and
breeding success of black grouse Tetra tetrix. Journal of Applied Ecology 33: 54-62.
Baxter A, Bone S, Pringle H, Eassom A, Dennis N. 2007. Appendix 2: CSL Wild birds as
Vectors for the spread of AIV from poultry units in: Network Simualtions of Disease
Transmission in the Poultry Industry in GB. Defra Project SE4206.
BBC 2007. Farmers tense as avian flu nears. http://news.bbc.co.uk/1/hi/uk/4730020.stm
Bolton M, Butcher N, Sharp, F, Stevens D, Fisher G. 2007. Remote monitoring of nests using
digital camera technology. Journal of Field Ornithology 78(2): 213-220.
Charman E, Carpenter J, Gruar D. 2009. Understanding the causes of decline in breeding bird
numbers in England: a review of the evidence base for declining species in the woodland
indicator for England. RSPB Research Report No. 37.
Chiron F, Juillard R. 2007. Responses of songbirds to magpie reduction in an urban habitat.
Journal of Wildlife Management 71(8): 2624-2631.
Cote IM, Sutherland WJ. 1997. The effectiveness of removing predators to protect bird
populations. Conservation Biology, 11:395-405.
Cramp S, Perrins C. 1994. The Birds of the Western Palearctic, Volume 8: Crows to Finches.
Oxford University Press.
Defra (2006) http://www.defra.gov.uk/animalh/diseases/notifiable/ai/index.htm#history
Draycott RAH, Hoodless AN, Woodburn MIA, Sage RB. 2008. Nest predation of common
pheasants Phasianus colclicus. Ibis 150 (Suppl. 1): 37-44.
Eaton MA, Brown AF, Noble DG, Musgrove AJ, Hearn R, Aebischer NJ, Gibbons DW,
Evans A, Gregory RD (2009) Birds of Conservation Concern 3: the population status of
birds in the United Kingdom, Channel Islands and the Isle of Man. British Birds 102,
pp296-341. http://www.bto.org/sites/default/files/u12/bocc3.pdf
Evans KL. 2004. The potential for interactions between predation and habitat change to cause
population declines of farmland birds. Ibis 146: 1-13.
Freeman SN, Crick HQP. 2003. The decline of the spotted flycatcher Muscicapa striata in the
UK: an integrated population model. Ibis 145: 400-412.
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Fuller RJ, Noble DG, Smith KW, Vanhinsbergh D. 2005. Recent declines in populations of
woodland birds in Britain: a review of possible causes. British Birds 98: 116-143.
Gibbons DW, Amar A, Anderson GQA, Bolton M, Bradbury RB, Eaton MA, Evans AD,
Grant MC, Gregory RD, Hilton GM, Hirons GJM, Hughes J, Johnstone I, Newberry P,
Preach WJ, Ratcliffe N, Smith KW, Summers RW, Walton P, Wilson JD. 2007. The
predation of wild birds in the UK: a review of its conservation impact and management.
RSPB Research Report No. 23, RSPB, Sandy.
Goodwin D. 1955. Jays and Carrion Crows recovering hidden food. British Birds 48: 181-183.
Gregory RD, Marchant JH. 1995. Population trends of Jays, Magpies, Jackdaws and Carrion
Crows in the United Kingdom. Bird Study 43: 28–37.
GWCT 2009. Conserving the grey partridge: A practical guide produced by the Game and
Wildlife Conservation Trust for farmers, landowners and local Biodiversity Action Plan
groups.
Holyoak D. 1968. A comparative study of the food of some British Corvidae. Bird Study
15(3): 147-153.
Major RE, Kendal CE. 1996. The contribution of artificial nest experiments to understanding
avian reproductive success: a review of methods and conclusions. Ibis 138: 298-307.
Martin TE. 1993. Nest predation among vegetation layers and habitat types: revising the
dogmas. American Naturalist 141: 897-913.
Moller AP. 1989. Nest site selection across field-woodland ecotones: the effect of nest
predation. Oikos 56: 240-246.
Moore RP, Robinson WD. 2004. Artificial bird nests, external validity, and bias in ecological
field studies. Ecology 85(6): 1562-1567.
Newson SE, Rexstad EA, Baillie SR, Buckland ST, Aebischer NJ. 2010. Population change of
avian predators and grey squirrels in England: is there evidence for an impact on avian
prey populations. Journal of Applied Ecology 47: 244-252.
Newton I. 1993. Predation and limitation of bird numbers. In: Current Ornithology (ed. D.M.
Power), pp. 143-198. Plenum Press, New York.
Newton I. 1998. Population Limitation in Birds. Academic Press, London.
Nordstrom M. 2003. Introduced predator in Baltic sea archipelagos: variable effects of feral
mink on bird and small mammal populations. 118 p. Turun Yliopisto, Turku.
O’Connor RJ. 1991. Long-term bird population studies in the US. Ibis, 133: s30-s48.
Paradis E, Baillie SR, Sutherland WJ, Dudley C, Crick HQP, Gregory RD. 2000. Large-scale
spatial variation in the breeding performance of song thrushes Turdus philomelos and
blackbirds T. Merula in Britain. Journal of Applied Ecology 37 (Suppl. 1): 73-87.
Rands MRW. 1988. The effect of nest site selection on nest predation in Grey Partridge
Perdix perdix and Red-legged Partridge Alectoris rufa. Ornis Scandinavica 19:35-40.
Remes V. 2005. Birds and rodents destroy different nests: a case study of Blackcap Sylvia
atricapilla using the removal of nest concealment. Ibis 147: 213-216.
Ricklefs R. 1969. An analysis of nesting mortality in birds. Smithsonian Contributions to
Zoology 9: 1-48.
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Risely K, Renwick AR, Dadam D, Eaton MA, Johnston A, Baillie SR, Musgrove AJ, Noble
DG. 2011. The Breeding Bird Survey 2010. BTO Research 597. Britisih Trust for
Ornithology, Thetford.
Robertson P. 1997. A Natural History of the Pheasant. Swan Hill Press.
Schaefer T. 2004. Video monitoring of shrub-nests reveals nest predators. Bird Study 51: 170177.
Sirawardena GM. 2004. Possible roles of habitat, competition and avian nest predation in the
decline of the Willow Tit Parus montanus. Bird Study 51: 193-202.
Smith RK, Pullin AS, Stewart GB, Sutherland WJ. 2010. Effectiveness of predator removal
for enhancing bird populations. Conservation Biology 24(3): 820-829.
Stahl P, Ruette S, Gros L. 2002. Predation on free-ranging poultry by mammalian and avian
predators: field loss estimates in a French rural area. Mammal Review 32(3): 227-234.
Stevens DK, Anderson GQA, Grice PV, Norris K. 2007. Breeding success of Spotted
Flycatchers Muscicapa striata in southern England – is woodland a good habitat for this
species? Ibis 149 (Suppl. 2): 214-223.
Stevens DK, Anderson GQA, Grice PV, Norris K, Butcher N. 2008. Predators of spotted
flycatcher Muscicapa striata nests in southern England as determined by digital nestcameras. Bird Study 55: 170-187.
Stoate C, Szczur J. 2001. Could game management have a role in the conservation of
farmland passerines? A case study from a Leicestershire farm. Bird Study 48: 279-292.
Weidinger K. 2009. Nest predators of woodland open-nesting songbirds in central Europe.
Ibis 151: 352-360.
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7. Appendix I
Birds of conservation concern
Eaton et al. 2009 (http://www.rspb.org.uk/Images/BoCC_tcm9-217852.pdf)
The UK's birds can be split in to three categories of conservation importance - red, amber and
green. Red (52 species) is the highest conservation priority, with species needing urgent
action. Amber (126 species) is the next most critical group, followed by green (68 species).
The criteria used in assessments are intended to ensure that Birds of Conservation Concern
(BoCC) listings reflect each species’ global and European status as well as that within the
UK, and additionally measure the importance of the UK population in international terms.
Red listing criteria:
 IUCN Global Conservation Status. Species listed by BirdLife International as being
Globally Threatened using IUCN criteria.
 Historical Decline. A severe decline in the UK between 1800 and 1995, without
substantial recent recovery.
 Breeding Population Decline. Severe decline in the UK breeding population size, of more
than 50%, over 25 years or the entire period used for assessments since the first BoCC
review, starting in 1969 (“longer-term”).
 Non-breeding Population Decline. Severe decline in the UK non-breeding population
size, of more than 50%, over 25 years or the longer-term.
 Breeding Range Decline. Severe decline in the UK range, of more than 50%, as measured
by number of 10 km squares occupied by breeding birds, over 25 years or the longerterm.
Amber listing criteria:
 SPEC European Conservation status. Categorised as a Species of European Conservation
Concern (SPEC 1, 2 or 3).
 Historical Decline – Recovery. Red listed for Historical Decline in a previous review but
with substantial recent recovery (more than doubled in the last 25 years).
 Breeding Population Decline. As for red list criteria, but with moderate decline (by more
than 25% but less than 50%).
 Non-breeding Population Decline. As for red list criteria, but with moderate decline (by
more than 25% but less than 50%).
 Breeding Range Decline. As for red list criteria, but with moderate decline (by more than
25% but less than 50%).
 Rarity. UK breeding population of less than 300 pairs, or non-breeding population of less
than 900 individuals.
 Localisation. At least 50% of the UK breeding or non-breeding population found in 10 or
fewer sites.
 International Importance. At least 20% of the European breeding or non-breeding
population found in the UK.
All regularly occurring species that do not qualify under any of the red or amber criteria are
green listed. The green list also includes those species listed as recovering from Historical
Decline in the last review that have continued to recover and do not qualify under any of the
other criteria.
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