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Bird Study

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Developing a quantitative index as a pragmatic aid to assessing implementation of European

Union Birds Directive site protection measures for individual species

Gwyn Williams, David A. Stroud, Graham J. M. Hirons, Jeremy D. Wilson & on behalf of the UK SPA & Ramsar Scientific Working Group

To cite this article: Gwyn Williams, David A. Stroud, Graham J. M. Hirons, Jeremy D. Wilson & on behalf of the UK SPA & Ramsar Scientific Working Group (2016) Developing a quantitative index as a pragmatic aid to assessing implementation of European Union Birds Directive site protection measures for individual species, Bird Study, 63:4, 447-458, DOI: 10.1080/00063657.2016.1211089 To link to this article:

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Developing a quantitative index as a pragmatic aid to assessing implementation of European Union Birds Directive site protection measures for individual species

Gwyn Williamsa, David A. Stroudb, Graham J. M. Hironsaand Jeremy D. Wilsoncon behalf of the UK SPA & Ramsar Scientific Working Group

aRSPB Centre for Conservation Science, RSPB, Sandy, Bedfordshire, UK;bJoint Nature Conservation Committee, Peterborough, UK;

cRSPB Centre for Conservation Science, RSPB Scotland, Edinburgh, UK


Capsule: A multi-element index is developed to help support decisions with respect to the establishment and review of national networks of European Union (EU) Special Protection Areas (SPAs).

Aims: To develop an index based on biological criteria which can be used to assess the sufficiency of protected area network coverage for national populations of individual bird species.

Methods: A Site Provision Index (SPI) was derived from data on species’ national and international distribution, population size, habitat use and site-fidelity. It was tested against the results of past UK policy and independent expert judgement.

Results: Index values were calculated for all regularly occurring UK birds for which the EU Birds Directive indicates that SPA provision should be considered. Index values and expert opinion on the percentage of populations of species expected to be found in a national network of protected areas were highly correlated. Indices also strongly correlated with existing provision of SPA protection for populations. Residuals from this regression relationship highlight objectively those species where consideration of further SPA provision may be necessary.

Conclusion: The SPI can provide a decision-support tool, through a form of gap analysis, to help identify where there is a significant difference between current protected area provision for a species and the level of provision that might be expected relative to other species with similar distribution and ecology.

ARTICLE HISTORY Received 30 March 2016 Accepted 5 July 2016

Wildlife is unevenly distributed in space. This reflects natural variation in ecological conditions such as habitat, climate, topography and geology. Increasingly however, human use of the environment has modified species’

distributions, with a preponderance of reductions in species abundance and range in heavily human-modified regions (Millennium Ecosystem Assessment 2005). In response, the protection of places especially rich for wildlife, where habitats can be subject to appropriate directed management, has become a fundamental tool of contemporary biodiversity conservation (Ratcliffe 1977, Schafer1990, Holdgate1999, Lawton et al.2010).

In the UK, site protection measures have been promoted for well over a century, first through the acquisition of land as nature reserves and later through statutory protection (Sheail 1976, Marren 2009). In addition, over time, protected area science and policy has moved from consideration of specific sites for particular species to evaluating how sites function as a network, both for the species they protect and their wider ecosystem function (e.g. Langhammer et al.

2007, Romão et al. 2012). In many cases, such as migratory birds which are a shared international heritage, protected area networks thus extend far beyond the boundaries of an individual nation state.

The European Communities Council Directive on the Conservation of Wild Birds (Directive 79/409 of 2 April 19791— ‘the Birds Directive’) was one product of the growth of environmental awareness in Europe during the 1960s and 1970s (Temple-Lang 1982). It was designed to halt declines in bird populations through a combination of general habitat and species protection measures for all birds, supported by targeted special conservation measures. These latter measures apply to those listed on Annex I of the Directive, and cover both highly threatened species2 and regularly occurring migratory species, with particular attention paid to wetlands of international importance (a cross-reference to the 1971 Ramsar Convention on wetland conservation; Temple-Lang 1982). These special conservation measures were to include the classification of especially important habitats (‘the most suitable

© 2016 British Trust for Ornithology

CONTACT David A. Stroud Joint Nature Conservation Committee, Monkstone House, City Road, Peterborough PE1 1JY, UK Tables of data values are available at

VOL. 63, NO. 4, 447–458


territories’) as Special Protection Areas (SPAs) to the extent necessary to meet the‘protective requirements of the species’.

Three decades later, the Birds Directive has been of fundamental importance in stimulating the establishment of a functionally coherent network of protected sites for birds across Europe (Romão et al.

2012). Not only has it been a successful legal instrument in administrative terms (Dodd et al. 2010) but there is increasing evidence of its contribution to European bird conservation. For example, there is a positive association at a continental scale between mean species trends of Annex I and migratory species, and the proportion of land classified as SPAs (Donald et al.2007, Sanderson et al.2016).

A recurrent problem, however, is the extent of land (or sea) which should be classified as SPA. The Directive itself provides no guidance on the selection of ‘most suitable territories’ or how to determine whether the ‘protective requirements of the species’ have been met. This is despite the fact that, depending on their ecology, species vary greatly in the extent to which protected area measures are likely to be an appropriate conservation response. For example, some species are so dispersed across the landscape that a very large area of land would have to be designated in order to embrace a substantial proportion of the population concerned. In such cases it may be more appropriate to deliver protective requirements by the promotion of special conservation measures in the wider countryside, with a reduced reliance on the classification of specific SPAs. Conversely, species which are aggregated persistently in the same few locations may be best served by the classification of SPAs which protect a high proportion of their populations. Conservation theory and practice (e.g. Schafer 1990) suggested that those species which should have the highest proportion of their population within a protected area network would be those which had more of the following characteristics:

occurring locally in high densities (congregatory species);

occurring to a large extent on natural or semi-natural habitats;3 showing predictable occurrence at particular sites regularly between years; having restricted national or international ranges; having small national4 or international population sizes.

In the UK, the statutory approach to this challenge has to date been based on a two-stage process (JNCC 1999) that makes only second-order use of some of the ecological and demographic characteristics of species suggested by Schafer (1990). The first stage identifies sites meeting internationally accepted numeric guidelines for designation intended to identify sites exceeding national importance thresholds for Annex I species (1% of national breeding or non-breeding

population), sites exceeding international importance thresholds for migratory species (1% of a biogeographic population) and sites supporting important assemblages of birds (over 20 000 individuals of all relevant species combined present at a site). A second stage then selects those considered as ‘most suitable territories’ (Stroud et al. 2001). Stage 2 evaluations are based on site- specific factors such as location in a species’ range, population size and density supported, breeding success, history of occupancy, naturalness (sensu Ratcliffe1977) and role as a severe weather refuge, and thus do take into account some of the characteristics suggested by Schafer (1990). Based on this approach, formal assessments of the scope and content of the national SPA network have been published periodically, the last in 2001, reflecting increasing knowledge of species’

distribution and ecology, and their key sites (Stroud et al. 1990, Pritchard et al. 1992, Way et al. 1993, Stroud et al.2001).

However, we do not know whether this site-by-site approach meets the protective requirements of the species concerned, as required by the Directive. When these sets of sites are compared with site inventories generated by BirdLife International (Important Bird Areas – IBAs – Heath & Evans 2000) based on biological criteria,5 the outcomes can differ. For example, Heath & Evans (2000) identify sites that, in combination, would cover 80% of the Chough Pyrrhocorax pyrrhocorax population in the UK. By 2001 however, SPAs had been classified for only 33% of the population (Stroud et al. 2001). Given that IBA inventories are accepted by the ECJ as a guide to national performance in SPA designation in the absence of national evaluations published by the Member State, then discrepancies like this generate debate between statutory and voluntary conservation bodies. This has slowed both the implementation of Birds Directive provisions, and agreement on when the network should be regarded as complete. At a European scale, the Ornis Committee’s Scientific Working Group (the technical advisory group to support the strategic development and implementation of the Directive) has been debating for significantly more than a decade, without resolution, European Union (EU)-wide approaches on a mechanism to test the extent to which a Member State’s protected area network might be determined as being complete.

An early contribution by Bezzel (1980) for the European Commission focused on the assessment of species range, evenness of distribution, population size and population trends, and was developed further in the UK by the then Nature Conservancy Council (Stroud et al. 1990). The resultant index scores were converted to five bands of target coverage within the UK SPA network, based on the proportion of a species’


population encompassed by the network. However, such a target driven approach to the establishment of the SPA network was not further developed by the statutory conservation agencies, in part because some considered it too deterministic.

Here we consider whether a more explicit consideration of the biological and demographic characteristics of species as suggested by Schafer (1990) might help to resolve debates over sufficiency of protected areas networks.

Specifically, we develop a simple quantitative approach to inform more objective judgements of sufficiency of SPA provision for individual bird species based on aspects of their distribution, ecology and life history characteristics.6It comprises four stages:

(i) calculation of a Site Provision Index (SPI) for each species;

(ii) testing the strength of correlation between SPI values and the judgement of ornithological experts of the proportion of species’ populations that should be contained within protected area networks;

(iii) modelling the form and strength of the relationship between SPI values and the proportion of species populations in SPAs in Great Britain (GB) at the time of the UK’s second SPA network Review (Stroud et al.2001) and

(iv) if this relationship is robust, using residuals from the best-fit relationship to inform reviews of the sufficiency of network provision for individual species.


Construction of the SPI

The starting point is to ascribe numerical values to the ecological and demographic characteristics identified by Article 4 of the Birds Directive and/or by Schafer (1990) and Stroud et al. (2001). In contrast to Stroud et al. (1990), we do not also consider a separate parameter describing conservation status, as the typical elements of such status evaluations (e.g. population size, range and degree of localization) are already within the set of index variables. We do not consider population trend as a factor since, although this is an important element in assessing whether a species should be considered a priority for conservation action (e.g. Eaton et al.2015), it does not in itself inform the appropriate mechanisms through which conservation measures should be delivered.

The attributes used as the basis for the SPI were linked conceptually to factors either identified by Article 4 of the Directive, and/or previously identified by Stroud

et al. (2001), and are shown in Table 1, with further information on the data and scoring used to produce the SPI in Table 2. The data used were those already collated from the mid-1990s for the purposes of the second complete review of the UK SPA network, published in 2001 (Stroud et al. 2001). Each of the attributes was given a score ranging from zero to six, split into six categories for quantitative factors and three for qualitative factors. As shown in Table 2, the band widths used for population sizes and national distributions are smaller for the rarest populations.

SPI values for each species were calculated by summing attribute scores and then converting to a proportion of the maximum possible value (48). This was done for all regularly occurring migratory and Annex I species in GB.7 The list of migratory species assessed follows that given in Appendix 3 of Stroud et al. (2001). Migratory Annex I species were treated according to their Annex I status, and scores were calculated separately for the breeding and non-breeding seasons. It is important to note that the expression of the SPI as a percentage should not itself be interpreted as a percentage ‘target’

for representation of that population by the SPA network. We excluded only Scottish Crossbill Loxia scotica, because its population was not assessed reliably until very recently (Summers & Buckland2011), and the re-established Red Kite Milvus milvus (in Scotland and England) and White-tailed Eagle Haliaetus albicilla populations. For the latter it was decided that no SPAs should be selected for these species during the current dynamic phase of establishment of natural distributions following re-establishments (Stroud et al.2001).

Quantifying expert judgement

Fifty-three respondents were drawn from the community of ornithologists with either past or current UK expertise, mainly within the statutory and non-governmental sectors. Specifically, the survey asked respondents to:

indicate the proportion of the GB population of the following birds you would expect tofind in a national network of internationally important protected areas having regard to the ability of protected areas to contribute to delivery of the ecological requirements of each species.

They were asked to do this for each of 45 species (listed in the Appendix) selected to cover a range of Annex I and migratory species, breeding and non-breeding populations, and across the full range of SPI values.

The sequence of species presented to respondents was alphabetic within four categories (Annex I or migratory


and non-Annex I; breeding or non-breeding). The mean value across all respondents was used in further analysis.

Comparison of SPI values with expert judgement We calculated the Pearson correlation coefficient to test the degree to which the SPI accords with expert judgement of the percentages of populations of species that it was expected should be within the national

network of internationally important protected areas.

We did this separately for breeding and non-breeding populations.

Comparison of SPI values with species representation in the SPA network

There is no SPA provision for many species (5 of 42 Annex I species and 92 of 120 non-Annex I species).

Table 1.Birds Directive criteria, conceptual objectives and their relationship to index elements.

Criteria given in Article 4 of Birds Directive

Factor identified in 2001 SPA Review (Stroud et al.2001)

Factor from UK SPA selection guidelines

(JNCC1999) SPI element

Relevant underpinning conservation science

Species vulnerable to specific changes in their habitat

Local occurrence in high densities (congregatory species)

Stage 2: Population size and density

Local occurrence in high densities

High density presence increases the proportion of populations which may be impacted by loss or degradation of individual important sites, but conversely conservation of these areas facilitates protection of significant population components at these few locations: (Heath & Evans 2000; Langhammer et al.2007;

Ramsar Convention2012) Occurrence, to a large extent, on

natural or semi-natural habitats

Stage 2: Naturalness Occurrence on natural/

semi-natural habitats

Typically, many natural and semi-natural habitats have unfavourable conservation status cf. intensively managed agricultural or other highly modified habitats e.g. European Commission (2015)

Predictable and regular occurrence at particular sites between years (i.e. species that are not irregular or dispersive)

Stage 2: History of occupancy

Predictable occurrence Occurrence that is predicable at specific locations increases risk when that location is subject to adverse change (Gilpin & Soulé 1986) but facilitates the protection of populations that regularly use those sites. Regular (predictable) use is the basis of established criteria for identification of sites of international importance (Heath &

Evans2000for IBAs; Stroud et al.

2001for SPAs in UK; Ramsar Convention2012for Ramsar Sites;

Langhammer et al.2007for IUCN’s Key Biodiversity Areas)

Species considered rare because of restricted local distribution

Restricted national or international ranges

Restricted national and international ranges

Restricted range is a well- established extinction risk factor:

Mace & Lande (1991); Committee on Scientific Issues in the Endangered Species Act (1995);

Soulé (1987); IUCN (2001) and others

Species in danger of extinction

Species considered rare because of small populations

Small national or international population sizes

Restricted national and international population sizes

Small population size is a well- established extinction risk factor:

Mace & Lande (1991); Mace (1994);

Committee on Scientific Issues in the Endangered Species Act (1995); Soulé (1987); IUCN (2001) and others

Article 4.2 specifically highlights the importance of staging areas for migratory species

Flyway scale connectivity of site networks: the degree to which species depend on linked networks of definable sites along an internationalflyway

Predictable occurrence Local occurrence in

high densities

The sequential use of key sites through the annual cycle is critical to the conservation of many migratory birds, for example, Piersma & Lindström (2004); Boere et al. (2006); Delany et al. (2009) and others. Predictable occurrence of a species at a location is important if that site is to be subject to conservation measures


Table 2.Attributes which comprise the SPI.

Local occurrence in high densities Occurrence on natural/semi-natural habitats

Attribute Score Attribute Score

>50% of GB breeding or non-breeding population at <ten sites (= respectively, localized in the breeding season (BL) or non-breeding season (WL) of Gregory et al.2002)

6 Occurrence exclusively on natural habitats, or on semi-natural habitats with high naturalness, high nature conservation values and limited management inputs


>50% of GB breeding or non-breeding population at <20 sites (expert assessment of moderately aggregating species)

Not as above

Evaluation data: Total number of GB 10 km sqs with breeding occupancy or total number of British & Irish 10 km sqs occupied in winter

Data sources: Lack (1986) and Gibbons et al. (1993)

3 0

Not exclusively occurring on natural or semi-natural habitats, with significant use of managed habitats (including low intensity farmland of high nature conservation value)

Not occurring on natural or semi-natural habitats to any great extent.

Occurrence largely on habitats that are either man-made (e.g. urban) or subject to major and/or artificial management inputs (e.g. intensive cereal/grass crops) with low nature conservation values

Evaluation data: Expert assessment based on literature sources Data sources: BWP (19771994); Tucker & Evans (1997); Snow & Perrins

(1998) and Baker & Stroud (2007)



Predictable occurrence

Attribute Score

Sites of importance for species well defined (sometimes with traditional nest structures) with annual predictable occurrence

6 Sites of importance for species less well defined with occurrence more


3 Population essentially labile, settling annually where suitable habitat

occurs, with largely unpredictable occurrence

0 Evaluation data: Expert assessment based on literature sources

Data sources: BWP (19771994) and Snow & Perrins (1998)

Restricted national range: breeding season Restricted national range: non-breeding season

<99 sqs 6 Attribute (%) Score

100–299 5 <16 6

300–599 4 17–33 5

600–999 3 34–50 4

1000–1499 2 51–66 3

1500–2099 1 67–83 2

>2100 sqs 0 84–100 1

Evaluation data: Total number of 10 km sqs with breeding occupancy during 1988 91 BTO Atlas (maximum potential no. 10 km sqs in GB = 2780), allocated to ranks as above

Evaluation data: Proportion of 10 km squares in Britain and Ireland with records during the 1981/2–83/4 BTO Winter Atlas period allocated to ranks as above Data source: Lack (1986)

Data source: Gibbons et al. (1993)

Restricted international range: breeding season Restricted international range: non-breeding

Attribute Score Attribute (%) Score

1–6 countries 6 <16 6

7–12 5 17–33 5

13–18 4 34–50 4

19–24 3 51–66 3

25–30 2 67–83 2

31–36 1 84–100 1

>37 0

Evaluation data: Numbers of European countries where breeding occurs drawn from EBCC Atlas of European breeding birds

Evaluation data: Estimated proportion of Europe where species occurs in the non- breeding season (excluding Russia, Ukraine and Belarus)

Data source: Hagemeijer & Blair (1997) Data source: From Snow & Perrins (1998). Range extent estimated by eye relative to total possible occurrence (= 100%).

Size of national population Size of international population

Population size Score Population size Score

1–99 6 1–99 6

100–999 5 100–999 5

1000–9999 4 1000–9999 4

10 000–99 999 3 10 000–99 999 3

100 000–999 999 2 100 000–999 999 2

1 000 000–9 999 999 1 1 000 000–9 999 999 1

>10 000 000 0 >10 000 000 0

Evaluation data: Population numbers in both breeding and non-breeding seasons.

Mid-point of ranges taken. Units are pairs in breeding season and individuals in non-breeding season. Ranks are orders of magnitude

Data sources: As given by Stroud et al. (2001)

Evaluation data: Biogeographic population sizes are for Europe excluding European Russia and Turkey. Units are pairs in breeding season and individuals in non-breeding season. Ranks are orders of magnitude. Minimum of population ranges were taken

Data sources: Taken from Stroud et al. (2001); Lloyd et al. (1991); Hagemeijer & Blair (1997) for breeding species, and Wetlands International (2002) for non-breeding species

Notes: Data and information used to construct the SPI elements used the most complete data sources as contemporary as possible to the mid-1990s. For some elements, such as European breeding, or UK non-breeding distributions, the sources used (Hagemeijer & Blair1997, and Lack1986, respectively) were necessarily from earlier periods in the absence of more contemporary evaluations for the mid-1990s.


In part, this reflects previous generic policy decisions to regard some categories of species (e.g. widely dispersed migrants; species in a dynamic phase of colonization or re-establishment after re-introduction) as unsuited to site protection mechanisms, thus fixing the proportion of the populations of those species in SPAs designated for those species at zero. We therefore first tested, using a one-way ANOVA whether SPI values were higher for species for which a proportion of the population is explicitly protected by the SPA network than those without SPA provision. For those species with SPA provision, we then used least squares linear regression to test whether variation in the proportion of species’ GB populations found in SPAs selected for that species (hereafter referred to as the SPA population8) is explained by the SPI, and the form of that relationship. These analyses were carried out separately for breeding and non-breeding seasons, and Annex I and non-Annex I species (four tests in total) and drew data from Stroud et al. (2001). The data used here therefore take no account of more recent (post- 2001) classifications of additional SPAs for some species such as Golden Eagle, Capercaillie and Chough (Stroud et al.2016). In all models, we sought tofit Family nested within Order as a random effect to account for any non-independence between closely related species (Jiguet et al.2010, Sanderson et al. 2016). For some of the models of SPA population coverage as a function of SPI value for species with SPA provision, covariance patterns allowed us to simplify this random effect to fit only Order (non-breeding populations of Annex I species) or to remove the random effect completely (non- breeding populations of non-Annex I species). Models were fitted using the GLIMMIX procedure in SAS 9.4, and degrees of freedom were calculated using the Kenward–Roger method.

Results SPI values

SPI values (percentage of maximum) for non- breeding Annex I species range from 0.4 (Kingfisher) to 0.88 (Greenland White-fronted Goose, Greenland and Svalbard populations of Barnacle Goose and Fair Isle Wren Troglodytes troglodytes fridariensis), whilst for breeding Annex I species they ranged from 0.38 (Short-eared Owl) to 0.88 (Fair Isle Wren). For non-breeding, non-Annex I migratory species values range from 0.04 (Chaffinch Fringilla coelebs) to 0.93 (Svalbard population of Light-bellied Brent Goose Branta bernicla hrota) and for breeding migratory species

from 0.04 (Woodpigeon Columba palumbus, Robin, Blackbird Turdus merula, Starling Sturnus vulgaris and Chaffinch) to 0.83 (Whimbrel). Annex I species had significantly higher SPI values than non-Annex I migratory species both in the breeding season (Annex I mean = 0.68 ± (se) 0.02, non-Annex I mean = 0.39 ± (se) 0.02, P < 0.001), and non-breeding season (Annex I mean = 0.63 ± (se) 0.03, non-Annex I mean = 0.42 ± (se) 0.03, P < 0.001).

Comparison with expert judgement

Fifty-three respondents completed the survey. Not all respondents provided evaluations for all species, based on lack of personal knowledge of some species. Sample sizes for different species’ evaluations therefore ranged from 38 to 53. Most respondents (81%) were currently professionally employed in bird conservation with more employed in the UK non-government sector (53%) than the statutory sector (28%). Nearly all respondents had background expertise in either the identification and/or classification of protected areas for birds (47%), and/or protected area management (41%), and/or other aspects of bird conservation such as policy or research (78%).

SPI values and the mean percentage of the GB population of species that respondents expected tofind protected by the national SPA network were very highly positively correlated (breeding populations, Pearson r = 0.9, n = 45, P < 0.001; non-breeding populations Pearson r = 0.91, n = 45, P < 0.001. There were no systematic differences in scores between respondents from governmental (GO) or non-governmental (NGO) organizations (mean for all scores for GO respondents

= 0.43 ± (se) 0.08; NGO = 0.41 ± (se) 0.04; paired t = 0.24; P = 0.813).

Comparison with species representation in the SPA network

Species with SPA provision have higher SPI values than species without such provision for Annex I breeding populations (t = 2.87, df = 39.8, P = 0.007) but not for non-breeding populations (t = 1.25, df = 17.9, P = 0.23) and for both breeding (t = 6.51, df = 63 P < 0.001) and non-breeding (t = 8.3, df = 33, P < 0.001) populations of non-Annex I species.Figure 1 shows the relationships between SPI value and SPA population for Annex I and non-Annex I species with SPA provision in the breeding season and non-breeding season. There is a highly significant positive relationship between the proportion of the population protected by SPAs (%SPA) and SPI. This is true for both Annex I and


non-Annex I breeding populations (Annex I %SPA

=−0.467 + 1.512*SPI; t = 4.62, df = 32.9, P < 0.001;

non-Annex I %SPA =−0.541 + 1.646*SPI; t = 4.26, df = 26.0, P = 0.002), and Annex I and non-Annex I non-breeding populations (Annex I %SPA =−0.67 + 1.695*SPI; t = 3.34, df = 16.7, P = 0.004; non-Annex I

%SPA =−0.161 + 0.942*SPI; t = 4.82, df = 86, P < 0.001).

These results confirm a strong, positive relationship between the SPI and the proportion of a species’

population protected by the SPA network in 2001, and the scatter of individual species points around this relationship may be a useful pragmatic tool to inform periodic reviews of sufficiency of SPA coverage across the national bird fauna. For example, simply ranking the respective sets of species in each analysis according to raw residuals (yobserved–yfitted) (Table 3) allows attention to be focused on those species where coverage of the population by SPA at the time of the 2001 Review is low relative to the biological suitability of the species for conservation through protected area mechanisms, as reflected by the SPI. Similarly, this approach also recognizes those species where the SPA coverage of the population is greater than expected from the statistical relationship with SPI, and thus

much more likely to be sufficient to meet the conservation needs of the species.


The SPI developed by this project was strongly correlated both with population coverage by SPAs in GB, and with the expert assessment of population coverage expected from the species’ ecological and demographic characteristics. The residuals for individual species derived from the relationship between SPI and SPA population coverage, for both Annex I and non-Annex I species, and both in and outside the breeding season, provide a pragmatic resource for identifying those species where sufficiency of SPA coverage needs particular scrutiny during periodic reviews of the SPA network. Species with no SPA provision should always be scrutinized first, perhaps especially in the case of non-breeding populations of Annex I species where there is no significant tendency for species without SPA provision to have lower SPI values than those with SPA provision.

A weakness of our pragmatic approach to development of the SPI is that the effects of non- Figure 1.Relationships between SPI values and (non-zero) proportions of populations held within SPA designated for species, for (a) Annex I species in the breeding season, (b) non-Annex I species in the breeding season, (c) Annex I species in the non-breeding season and (d) non-Annex I species in the non-breeding season. Thefitted regression lines are described in more detail in Results section.


independence and alternative weightings of SPI attributes, and the informed but subjective assignment of scores within attributes (Table 2) have not been formally assessed via sensitivity analyses. There is also scope to further refine elements such as assessment of habitat use and occurrence. However, the fact that SPI is very strongly correlated with expert judgement suggests that it is robust in generating a simple quantitative framework to inform practical judgements regarding sufficiency of SPA provision made on a species-by-species basis.

The interpretation of SPI values for some speciesfits well with current implementation of SPAs, whilst for others it raises issues worthy of further exploration.

For example, amongst breeding species, the Whimbrel Numenius phaeopus is a boreal breeding species with large numbers occurring north of Britain in the Faeroes, Iceland, Scandinavia and Russia (Delany et al.

2009). Although it has a very high SPI (0.83), reflecting its limited breeding distribution and population size in the UK, and occurrence on semi-natural wet heath habitats, SPA provision is low with the single SPA of Fetlar containing just 12% of the British population in the 1990s. The disparity between SPA provision and SPI (Table 3) suggests review of the SPA suite would be opportune, especially given the current population decline (Eaton et al. 2015). Similarly, amongst non- breeding species, Purple Sandpiper Calidris maritima has a SPI of 0.72, yet only 9% of the population occur in just three SPAs. Stroud et al. (2001) recognized this low provision, and noted the need for further review of the SPA suite for this species.

Many abundant and widespread, migratory, non-Annex I species (e.g. Sky Lark Alauda arvensis and Goldcrest Regulus regulus) have very low SPI values (0.1 and 0.2, respectively, in these cases) and have no SPA provision, Table 3.Species with SPA provision where the proportion of the population protected by the SPA network is smaller than expected from the regression relationship with SPI. The species with the largest negative residual values have SPA provision which is furthest below the average for species of similar distribution and ecology and thus would be priority for attention in any review. Note that the data describe the situation in the 1990s and for several of the species (e.g. Capercaillie, Golden Eagle) there have been significant new SPA classifications since 2001.

Rank Breeding Annex I Residual Breeding non-Annex I Residual Non-breeding Annex I Residual


non-Annex I Residual 1 Storm Petrel

Hydrobates pelagicus −0.35 Whimbrel

Numenius phaeopus −0.68 Slavonian Grebe

Podiceps auritus −0.35 Long-tailed Duck

Clangula hyemalis −0.49 2 Spotted Crake

Porzana porzana −0.28 Arctic Skua

Stercorarius parasiticus −0.33 Whooper Swan

Cygnus cygnus −0.23 Purple Sandpiper

Calidris maritima −0.45 3 Golden Eagle

Aquila chrysaetos −0.20 Greenshank

Tringa nebularia −0.31 Chough

Pyrrhocorax pyrrhocorax −0.21 Turnstone

Arenaria interpres −0.39

4 Chough

P. pyrrhocorax −0.18 Redshank

Tringa totanus −0.27 Ruff

Philomachus pugnax −0.17 Common Scoter

Melanitta nigra −0.38 5 Red Kite (native)

Milvus milvus −0.16 Cormorant

Phalacrocorax carbo −0.25 Greenland White-fronted Goose

Anser albifrons

−0.17 Scaup

Aythya marila −0.37

6 Osprey

Pandion haliaetus

−0.16 Common Gull Larus canus

−0.19 Golden Eagle Aquila chrysaetos

−0.16 Velvet Scoter Melanitta fusca

−0.37 7 Slavonian Grebe

Podiceps auritus

−0.15 Great Black-backed Gull Larus marinus

−0.19 Bittern

Botaurus stellaris

−0.14 Eider

Somateria mollissima

−0.37 8 Dotterel

Charadrius morinellus

−0.13 Common Scoter Melanitta nigra

−0.16 Bar-tailed Godwit Limosa lapponica

−0.10 Whimbrel

Numenius phaeopus

−0.31 9 Red-throated Diver

Gavia stellata

−0.12 Gadwall Anas strepera

−0.13 Greenland Barnacle Goose Branta leucopsis

−0.07 Goosander Mergus merganser

−0.25 10 Merlin

Falco columbarius

−0.11 Shag

Phalacrocorax aristotelis

−0.09 Capercaillie Tetrao urogallus

−0.07 Goldeneye Bucephala clangula

−0.20 11 Red-necked Phalarope

Phalaropus lobatus

−0.10 Black-headed Gull Chroicocephalus ridibundus

−0.07 Little Egret Egretta garzetta

−0.05 Ringed Plover Charadrius hiaticula


12 Arctic Tern

Sterna paradisaea −0.08 Ringed Plover

Charadrius hiaticula −0.05 Pochard

Aythya ferina −0.13

13 Peregrine

Falco peregrinus −0.07 Snipe

Gallinago gallinago −0.13 14 Honey Buzzard

Pernis apivorus −0.06 Tufted Duck

Aythya fuligula −0.10 15 Capercaillie

Tetrao urogallus −0.05 Great Crested Grebe

Podiceps cristatus −0.07 16 Nightjar

Caprimulgus europaeus

−0.03 Bean Goose

Anser fabalis −0.07

17 Sandwich Tern Sterna sandvicensis

−0.03 Red-breasted Merganser

Mergus serrator

−0.02 18 Mediterranean Gull

Larus melanocephalus

−0.00 Mallard

Anas platyrhynchos



reflecting a belief that conservation provision is better delivered through wide-scale policy instruments rather than site protection. For many farmland species there has been much research-driven development of agri-environment policy and provision in recent years which supports that view (Wilson et al.2009). However, it should be noted that levels of funding for agri-environment measures have so far only succeeded in reversing declines of species that had become rare and range-restricted such as Corncrake and Stone-curlew Burhinus oedicnemus, and have yet to do the same for species which remain more widespread such as Lapwing Vanellus vanellus or Sky Lark (Wilson & Bradbury2015).

With Common Agricultural Policy budgets coming under increasing scrutiny and pressure, it may be necessary to re-visit long-held policy assumptions that there exist good alternatives to site protection mechanisms to secure the conservation of species with low SPI values.


We consider that the approach presented here is promising in terms of meeting our stated purpose – providing a pragmatic approach to help assess the sufficiency of a protected area network for individual bird species. We believe that it meets the standards originally suggested by Bezzel (1980) in that it summarizes ecological information succinctly; makes it more, rather than less, accessible to decision makers; is capable of being deployed at differing geographical scales, and can be supplemented in extremis by expert judgement in cases of data deficiency.

We suggest that the SPI should not be used deterministically, but is best used as a part of a decision-support tool to help identify where there are significant differences between current site provision for a species, and the level of provision that might be expected relative to other species. It should be used to facilitate a more objective, biological foundation for discussions of the sufficiency of species’ SPA suites.

Residuals from regression analysis of SPA provision on SPI for specified groups of species in effect provide a gap analysis to assist assessments of the sufficiency of SPA suites as part of periodic SPA review processes. Of course, in such reviews, all relevant species should be considered as part of the process of assessing the overall coherence of the network in the face of change (e.g. Johnston et al. 2013). However, for a species whose SPA population is high relative to its SPI value, we would expect such an assessment process to be less detailed than, say for a species with low SPA provision relative to its SPI value or no SPA provision at all. In such cases, there may be a range of valid reasons for

low or zero SPA provision (e.g. irregular occurrence across multiple sites), but where this is not the case we would generally expect significant deficiencies to be addressed through the identification and classification of additional sites as SPAs. The only exception might be where a Member State has identified and is implementing a robust package of special conservation measures that would be considered by the European Communities to be a valid accompaniment to SPA classification within the meaning of Article 4.1 of the Birds Directive.

In a UK context we are applying the approach described here, with updated index values and contemporary assessments of SPA provision, in a current, third review of the UK SPA network (Stroud et al.2016).


1. Now replaced by the codified Directive 2009/147/EC which contains identical provisions.

2. Defined in Article 4(1) of the Directive as (i) species in danger of extinction; (ii) species vulnerable to specific changes in their habitat; (iii) species considered rare because of small populations or restricted local distribution and (iv) other species requiring particular attention for reasons for the specific nature of their habitat.

3. Since species dependant on natural or semi-natural habitat tend to be those vulnerable to loss or sensitive to management in contrast to those using more widely available and easy replaceable man-made habitats.

However, the European Court of Justice (ECJ) draws no distinction between man-made and natural habitats in the context of SPA classification.

4. And from a legal perspective, in Case C-418/04, the ECJ noted that a small national population (of Corncrake Crex crex in Ireland) ‘justifies a high level of site protection’.

5. BirdLife International has published regularly updated inventories of sites (IBAs) that meet objective criteria for SPA classification. These criteria include species of global conservation concern; species with restricted ranges or which occur in biomes that are themselves restricted; different types of congregatory species and species with unfavourable conservation status (Heath

& Evans2000).

6. Indeed in the specific context of Chough (above), the application of the approach described here led to the classification of three further SPAs for the species in 2006 and 2007 holding over 5% of the British population.

7. UK was not used as traditionally, assessment of SPAs in Northern Ireland has been undertaken in an All-Ireland biogeographic context (Way et al.1993). Stroud et al.

(2001) list these regularly occurring Annex I and migratory species.

8. Proportions of national populations with the SPA network vary according to diurnal movements between different sites. For some species, especially Anser geese, night-time roost sites have typically been classified as SPAs, whilst day-time feeding areas


generally have not. Different SPI values were calculated for some goose species on the basis on their day or night occurrence within SPAs, although for this paper we present just the occurrence values given by Stroud et al. (2001), that is, as related to currently classified SPAs which are mainly roost sites.


This work was undertaken in support of DEFRA’s SPA and Ramsar Scientific Working Group which advises on scientific issues related to the strategic development of the UK SPA network and in the specific context of the third network Review. We are grateful to all members of the Working Group for their help and advice in guiding this work, and especially to Sarah Anthony, Ian Bainbridge, Helen Baker, Nigel Buxton, Ben Fraser, Kate Jennings, Ant Maddock, Ed Mountford, Siân Whitehead and Andy Webb. We particularly thank Helen Baker for her support and discussion over many years. We are also grateful to those individuals who responded to the questionnaire and colleagues who assisted in its dissemination. We thank Ken Smith and Malcolm Ausden for earlier input and discussions of this work and also to Nigel Buxton, Andrew Dodd, Kate Jennings, Rachel Stroud and Siân Whitehead who kindly provided comments on a draft of this paper. The opinions of the authors presented here do not necessarily reflect the official positions of their supporting organizations.

Disclosure statement

No potential conflict of interest was reported by the authors.


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Appendix. The 45 bird species considered by the expert panel

White-fronted Goose Anser albifrons (Greenland and European populations separately), Barnacle Goose Branta leucopsis, Dark-bellied Brent Goose Branta bernicla bernicla, Mallard Anas platyrhynchos, Shoveler Anas clypeata, Capercaillie Tetrao urogallus, Manx Shearwater Puffinus puffinus, Storm Petrel Hydrobates pelagicus, Cormorant Phalacrocorax carbo, Bittern* Botaurus stellaris, Golden Eagle Aquila chrysaetos, Kestrel Falco tinnunculus, Merlin F. columbarius, Peregrine F. peregrinus, Corncrake Crex crex, Moorhen Gallinula chloropus, Oystercatcher Haematopus ostralegus, Avocet Recurvirostra avocetta, Ringed Plover Charadrius hiaticula, Golden Plover Pluvialis apricaria, Lapwing Vanellus vanellus, Knot Calidris canutus, Ruff Philomachus pugnax, Common Snipe Gallinago gallinago, Woodcock Scolopax rusticola,


Black-tailed Godwit* Limosa limosa, Bar-tailed Godwit L. lapponica, Whimbrel Numenius phaeopus, Redshank*

Tringa totanus, Red-necked Phalarope Phalaropus lobatus, Herring Gull Larus argentatus, Roseate Tern Sterna dougallii, Guillemot Uria aalge, Short-eared Owl Asio flammeus, Kingfisher* Alcedo atthis, Chough*, Woodlark Lullula

arborea, Blackcap Sylvia atricapilla, Dartford Warbler S. undata, Robin Erithacus rubecula, Pied Flycatcher Ficedula hypoleuca, Stonechat Saxicola rubicola and Snow Bunting Plectrophenax nivalis. For the five species marked with an asterix, assessments were made for both breeding and non-breeding seasons giving a total of 50 assessments.




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