Indicator Specification

Abundance and distribution of selected species in Europe

Indicator Specification
  Indicator codes: SEBI 001 , CSI 050
Published 12 May 2021 Last modified 12 May 2021
16 min read
This indicator shows trends in the abundance of common birds and butterflies across their European ranges  over time . It is a composite of many species trend indices. A value of 100 is set for each species in the start year. If a species is added to the composite index after the start year, it is scaled to the index value of the year it was added to the indicator.  

Assessment versions

Published (reviewed and quality assured)


Justification for indicator selection

Main advantages of the indicator:

Policy relevant: this indicator contributes to the assessment of biodiversity conservation policies and targets, as well as other sectoral and thematic policies and strategies.

Biodiversity relevant: birds and butterflies can be excellent barometers of the health of the environment. They occur in many habitats, can reflect changes in other animal and plant populations, and are sensitive to environmental change.

Scientifically sound and methodologically well founded: the methods used have been harmonised (national systems may differ but indices are standardised before being combined), and are peer-reviewed and statistically robust.

Monitors progress towards targets: this indicator provides a tangible basis for measuring progress towards biodiversity targets.

Broad acceptance and understanding: this indicator reports on birds and butterflies. Both species groups resonate strongly with the public, illustrating how citizen science can be exploited through effective targeting.

Routinely collected data.

Scientific references

  • No rationale references available

Indicator definition

This indicator shows trends in the abundance of common birds and butterflies across their European ranges over time. It is a composite of many species trend indices. A value of 100 is set for each species in the start year. If a species is added to the composite index after the start year, it is scaled to the index value of the year it was added to the indicator.



An index of relative values is used, with the value for 1990 set to 100.


Policy context and targets

Context description

The EU has been taking action to protect biodiversity for a considerable number of years, for example by adopting the Birds Directive — Council Directive 79/409/EEC (updated by Directive 2009/147/EC) and the Habitats Directive — Council Directive 92/43/EEC (EU, 1992, 2009).

In 2011, the first EU biodiversity strategy, ‘Our life insurance, our natural capital: an EU biodiversity strategy to 2020’, was adopted by the European Commission in line with the results of the 10th meeting of the Conference of the Parties to the Convention on Biological Diversity (CBD), held in Nagoya, Japan (October 2010). This strategy provided a framework for the EU to meet its own biodiversity objectives and global commitments as a party to the CBD. It was built around six mutually supportive targets that address the main drivers of biodiversity loss and aimed to reduce the key pressures on nature and ecosystem services in the EU; however, the targets have not been reached.

The publication of the ‘EU biodiversity strategy for 2030: Bringing nature back into our lives’ in May 2020 reinforces the relevance of this indicator, in particular the commitments of the EU nature restoration plan.

This indicator also needs to be considered in the context of the CAP, in particular its rural development policy 2014-2020 and the new farm to fork strategy (EC, 2021b, 2021d, 2021e). Relevant policy measures under the rural development policy include agri-environment-climate schemes and payments to farmers in areas with natural constraints or for adapted farming in areas with environmental restrictions, such as Natura 2000 sites.

Related policy documents:

  • EU biodiversity strategy to 2020 (EC, 2021c): there were six main targets, and 20 actions to help Europe reach these targets. The six targets covered:
    • full implementation of EU nature legislation to protect biodiversity;
    • better protection for ecosystems, and more use of green infrastructure;
    • more sustainable agriculture and forestry;
    • better management of fish stocks;
    • tighter controls on invasive alien species;
    • a bigger EU contribution to averting global biodiversity loss.
  • EU biodiversity strategy for 2030 (EC, 2021a): the European Commission has adopted a new EU biodiversity strategy for 2030 and an associated action plan — a comprehensive, ambitious, long-term plan for protecting nature and reversing the degradation of ecosystems. It aims to put Europe’s biodiversity on a path to recovery by 2030, with benefits for people, the climate and the planet. It aims to build our societies’ resilience to future threats such as climate change impacts, forest fires, food insecurity and disease outbreaks, including by protecting wildlife and fighting illegal wildlife trade. A core part of the European Green Deal, the biodiversity strategy will also support a green recovery following the COVID-19 pandemic.


EU 2020 Biodiversity Headline Target

Related policy documents

  • EU 2020 Biodiversity Strategy
    in the Communication: Our life insurance, our natural capital: an EU biodiversity strategy to 2020 (COM(2011) 244) the European Commission has adopted a new strategy to halt the loss of biodiversity and ecosystem services in the EU by 2020. There are six main targets, and 20 actions to help Europe reach its goal. The six targets cover: - Full implementation of EU nature legislation to protect biodiversity - Better protection for ecosystems, and more use of green infrastructure - More sustainable agriculture and forestry - Better management of fish stocks - Tighter controls on invasive alien species - A bigger EU contribution to averting global biodiversity loss
  • EU Biodiversity Strategy for 2030
    The European Commission has adopted the new  EU Biodiversity Strategy for 2030 and an associated Action Plan (annex)  - a comprehensive, ambitious, long-term plan for protecting nature and reversing the degradation of ecosystems. It aims to put Europe's biodiversity on a path to recovery by 2030 with benefits for people, the climate and the planet. It aims to build our societies’ resilience to future threats such as climate change impacts, forest fires, food insecurity or disease outbreaks, including by protecting wildlife and fighting illegal wildlife trade. A core part of the  European Green Deal , the Biodiversity Strategy will also support a green recovery following the COVID-19 pandemic.

Key policy question

Abundance and distribution of selected European species, aggregated assessment level

Specific policy question

Abundance and distribution of selected European species, disaggregated assessment level



Methodology for indicator calculation

Common birds

The data for this indicator originate from national monitoring data collected by the Pan-European Common Bird Monitoring Scheme (PECBMS). PECBMS is a partnership, involving the EBCC, the Royal Society for the Protection of Birds, BirdLife International and Statistics Netherlands, that aims to deliver policy-relevant biodiversity indicators for Europe. The PECBMS coordination unit is part of the Czech Society for Ornithology (CSO), based in Prague, Czechia. The unit collects national indices, produces European indices and indicators, prepares outputs for publication, and communicates outputs to the public, policymakers and scientists.

Trend information spanning different time periods is derived from annual national breeding bird surveys in 25 EU countries. Highly skilled volunteer ornithologists carry out counting and data collection. Data are collected nationally on an annual basis during the breeding season through common bird monitoring schemes. National bird monitoring data are gathered using several count methods (e.g. standardised point transects/line transects, territory mapping), using a variety of sampling strategies (from free choice of plots to stratified random sampling), and individual plot sizes vary within each country (from 1 × 1 km or 2 × 2 km squares or 2.5-degree grid squares to irregular polygons). 

Indicators (multi-species indices) are computed using the MSI-tool (R-script) for calculating multi-species indicators (MSIs) and trends in MSIs. The method of calculation is described in Soldaat et al. (2017). European, EU or regional species indices including standard errors are used as source data.

Country coverage (i.e. reflecting the availability of high-quality monitoring data from annually operated common bird monitoring schemes employing generic survey methods and producing reliable national trends): Austria (since 1998), Belgium (Brussels since 1992; Flanders since 2007; Wallonia since 1990), Bulgaria (since 2005), Cyprus (since 2006), Czechia (since 1982), Denmark (since 1976), Estonia (since 1983), Finland (since 1975), France (since 1989), Germany (since 1989), Greece (since 2007), Hungary (since 1999), Ireland (since 1998), Italy (since 2000), Latvia (since 1995), Lithuania (since 2011), Luxembourg (since 2009), the Netherlands (since 1984), Poland (since 2000), Portugal (since 2004), Romania (since 2007), Slovakia (since 2005), Slovenia (since 2008), Spain (since 1998) and Sweden (since 1975). 

The current population index of common birds was produced for the following 168 species:

  • Common farmland birds: Alauda arvensis, Alectoris rufa, Anthus campestris, Anthus pratensis, Bubulcus ibis, Burhinus oedicnemus, Calandrella brachydactyla, Carduelis cannabina, Ciconia ciconia, Corvus frugilegus, Emberiza cirlus, Emberiza citronella, Emberiza hortulana, Emberiza malanocephala, Falco tinnunculus, Galerida cristata, Galerida theklae, Hirundo rustica, Lanius collurio, Lanius minor, Lanius senator, Limosa limosa, Melanocorypha calandra, Miliaria calandra, Motacilla flava, Oenanthe hispanica, Passer montanus, Perdix perdix, Petronia petronia, Saxicola rubetra, Saxicola torquata, Serinus serinus, Streptopelia turtur, Sturnus unicolor, Sturnus vulgaris, Sylvia communis, Tetrax tetrax, Upupa epops and Vanellus vanellus.
  • Common forest birds: Accipiter nisus, Anthus trivialis, Bombycilla garrulous, Bonasa bonasia, Carduelis spinus, Certhia brachydactyla, Certhia familiaris, Coccothraustes coccothraustes, Columba oenas, Cyanopica cyanus, Dendrocopos medius, Dendrocopos minor, Dryocopus martius, Emberiza rustica, Ficedula albicollis, Ficedula hypoleuca, Garrulus glandarius, Nucifraga caryocatactes, Parus ater, Parus cristatus, Parus montanus, Parus palustris, Phoenicurus phoenicurus, Phulloscopus bonelli, Phylloscopus collybita, Phylloscopus sibilatrix, Picus canus, Pyrrhula pyrrhula, Regulus ignicapilla, Regulus regulus, Serinus citrinella, Sitta europaea, Tringa ochropus and Turdus viscivorus.
  • Other common birds: Acrocephalus arundinaceus, Acrocephalus palustris, Acrocephalus schoenobaenus, Acrocephalus scirpaceus, Actitis hypoleucus, Aegithalos caudatus, Alcedo atthis, Anas platyrhynchos, Apus apus, Ardea cinerea, Buteo buteo, Carduelis chloris, Carduelis flammea, Cettia cetti, Circus aeruginosus, Cisticola juncidis, Clamator glandarius, Columba palumbus, Corvus corax, Corvus corone, Corvus monedula, Cuculus canorus, Cygnus olor, Delichon urbica, Dendrocopos major, Dendrocopos syriacus, Egretta garzetta, Emberiza cia, Emberiza schoeniclus, Erithacus rubecula, Fringilla coelebs, Fringilla montifringilla, Fulica atra, Gallinago gallinago, Gallinula chloropus, Grus grus, Haematopus ostralegus, Hippolais icterina, Hippolais polyglotta, Hirundo daurica, Hirundo rupestris, Jynx torquilla, Larus ridibundus, Locustella fluviatilis, Locustella naevia, Lullula arborea, Luscinia luscinia, Luscinia megarhynchos, Luscinia svecica svecica, Merops apiaster, Motacilla alba, Motacilla cinerea, Muscicapa striata, Numenius arquata, Numenius phaeopus, Oenanthe cypriaca, Oenanthe oenanthe, Oriolus oriolus, Parus caeruleus, Parus major, Passer domesticus, Phasianus colchicus, Phoenicurus ochruros, Phylloscopus trochilus, Pica pica, Picus viridis, Pluvialis apricaria, Podiceps cristatus, Prunella modularis, Pyrrhocorax pyrrhocorax, Streptopylia decaocto, Sylvia atricapilla, Sylvia borin, Sylvia cantillans, Sylvia curruca, Sylvia hortensis, Sylvia melanocephala, Sylvia melanothorax, Sylvia nisoria, Sylvia undata, Tachybaptus ruficollis, Tadorna tadorna, Tetrao tetrix, Tringa erythropus, Tringa glareola, Tringa nebularia, Tringa tetanus, Troglodytes troglodytes, Turdus iliacus, Turdus merula, Turdus philomelos, Turdus pilaris and Turdus torquatus.

More information about species indices and trends is available at:

The PECBMS European species classification (farmland, forest and other) has been developed over time as the indicators have been published and refined. The first publication was based on European trends for 47 common bird species, classified by national coordinators of monitoring schemes and other experts who met at the PECBMS workshop in Prague in 2001. For the second publication, based on an enlarged species sample, the classification was improved and was based on a publication by Tucker and Evans (1997), describing habitats and their importance for birds in Europe. Since 2007, when the third set of European indices and indicators was published, data on over 150 species have been used and the species classification has been based on assessments within bio-geographical regions in Europe (see the PECBMS website for further details on the historic classification (EBCC, 2021b)).


The data for this indicator originate from the European Butterfly Monitoring Scheme (eBMS) (a joint initiative of Butterfly Conservation Europe and the Centre for Ecology & Hydrology) and the Assessing Butterflies in Europe (ABLE) project.

The butterfly sampling method is based on butterfly transect counts (Pollard and Yates, 1993). The eBMS provides methodological support to volunteers and country/regional networks, e.g. via the manual for butterfly transect counts (Sevilleja et al., 2019).

The butterfly indicator is based on the fieldwork of thousands of trained professional and volunteer recorders, counting butterflies on more than 6 200 transects scattered widely across the EU under standardised conditions. National coordinators collect the data and perform the first quality control step. In 2017, more than 55 880 km of transect walks were made, more than 90 % of them by volunteers, monitoring each transect an average of 15 times per year (van Swaay et al., 2019).

For each species and year, flight periods were estimated (Dennis et al., 2016) based on climate zones as defined in Metzger et al. (2013), but with further geographical stratification to represent major geographical units (e.g. Ireland was treated as a separate unit to continental Europe). Site-level indices were produced by estimating the missing counts, and species’ collated indices were produced for each monitoring scheme using a Poisson general linear model (GLM) with site and year effects, as well as the proportion of the flight period surveyed as a weighting. A collated index for the EU was produced for each species by fitting a Poisson GLM to the scheme-level collated indices with scheme and year effects as well as a weighting. The EU indices for the 17 species were combined by taking the geometric mean of the indices using the Biological Records Centre (BRC) indicators R package (GitHub, 2021). This indicator is a unified measure of biodiversity following the bird indicators as described by Gregory et al. (2005), by averaging indices of species rather than abundances to give each species an equal weight in the resulting indicators. If positive and negative changes of indices are in balance, their mean would be expected to remain stable. If more species decline than increase, the mean should go down, and vice versa. Thus, the index mean is considered a measure of biodiversity change.

For this updated indicator, data were used from 19 EU countries: Austria (since 2013), Belgium (since 1991), Czech Republic (since 2010), Estonia (since 2004), Finland (since 1999), France (since 2005), Germany (since 2005), Hungary (since 2016), Ireland (since 2007), Latvia (since 2015), Lithuania (since 2009), Luxembourg (since 2010), the Netherlands (since 1991), Romania (since 2013), Spain (since 1994), Slovenia (since 2007) and Sweden (since 2009).

The indicator is based on the following 17 species:

  • Widespread species: Anthocharis cardamines, Coenonympha pamphilus, Lasiommata megera, Lycaena phlaeas, Maniola jurtina, Ochlodes sylvanus and Polyommatus icarus.
  • Specialist species: Cupido minimus, Cyaniris semiargus, Erynnis tages, Euphydryas aurinia, Lysandra bellargus, Lysandra coridon, Phengaris arion, Phengaris nausithous, Spialia sertorius and Thymelicus acteon.

European butterfly experts selected 17 species that they considered to be characteristic of European grassland and that occurred in a large part of Europe, covered by the majority of the butterfly monitoring schemes, and with grasslands as their main habitat (van Swaay et al., 2006).



Brlík, V., et al., 2021, ‘Long-term and large-scale multispecies dataset tracking population changes of common European breeding birds’,Scientific Data8, 21 (DOI: 10.1038/s41597-021-00804-2).

Butchart, S. H. M., et al., 2010, ‘Global biodiversity: indicators of recent declines’,Science328(5982), pp. 1164-1168 (DOI: 10.1126/science.1187512).

Dennis, E. B., et al., 2016, ‘A generalized abundance index for seasonal invertebrates’,Biometrics72(4), pp. 1305-1314.

Donald, P. F., et al., 2001, ‘Agricultural intensification and the collapse of Europe’s farmland bird populations’,Proceedings of the Royal Society. B, Biological Sciences268(1462), pp. 25-29 (DOI: 10.1098/rspb.2000.1325).

EBCC, 2021a, ‘Pan-European Common Bird Monitoring Scheme — Trends and indicators’, European Bird Census Council ( accessed 15 April 2021.

EBCC, 2021b, ‘PECBMS’, European Bird Census Council ( accessed 15 April 2021.

EC, 2021a, ‘Biodiversity strategy for 2030 — concrete actions’, European Commission ( accessed 18 February 2021.

EC, 2021b, ‘Common agricultural policy’, European Commission ( accessed 14 April 2021.

EC, 2021c, ‘EU biodiversity strategy to 2020’, European Commission ( accessed 18 February 2021.

EC, 2021d, ‘From farm to fork’, European Commission ( accessed 15 April 2021.

EC, 2021e, ‘Rural development’, European Commission ( accessed 15 April 2021.

EU, 1992, Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora (OJ L 206, 22.7.1992, p. 7-50).

EU, 2000, Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for community action in the field of water policy (OJ L 327, 22.12.2000, p. 1-73).

EU, 2009, Directive 2009/147/EC of the European Parliament and of the Council of 30 November 2009 on the conservation of wild birds (OJ L 20, 26.1.2010, pp. 7-25).

Fraixedas, S., et al., 2015, ‘Population trends of common breeding forest birds in southern Finland are consistent with trends in forest management and climate change’,Ornis Fennica92, pp. 187-203.

GitHub, 2021, ‘BRCindicators’, Biological Records Centre ( accessed 22 April 2021.

Gregory, R. D., et al., 2005, ‘Developing indicators for European birds’,Philisophical Transactions of the Royal Society B360, pp. 269-288.

Guerrero, I., et al., 2012, ‘Response of ground-nesting farmland birds to agricultural intensification across Europe: landscape and field level management factors’,Biological Conservation152, pp. 74-80 (DOI: 10.1016/j.biocon.2012.04.001).

Metzger, M. J., et al., 2013, ‘A high‐resolution bioclimate map of the world: a unifying framework for global biodiversity research and monitoring’,Global Ecology and Biogeography22(5), pp. 630-638.

Musitelli, F., et al., 2016, ‘Effects of livestock farming on birds of rural areas in Europe’,Biodiversity and Conservation25(4), pp. 615-631 (DOI: 10.1007/s10531-016-1087-9).

Nilsson, S. G., et al., 2013, ‘Land-use changes, farm management and the decline of butterflies associated with semi-natural grasslands in southern Sweden’,Nature Conservation6, pp. 31-48 (DOI: 10.3897/natureconservation.6.5205).

Owens, A. C. S., et al., 2020, ‘Light pollution is a driver of insect declines’,Biological Conservation241, 108259 (DOI: 10.1016/j.biocon.2019.108259).

Pollard, E. and Yates, T. J., 1993,Monitoring butterflies for ecology and conservation, Springer Netherlands.

Sevilleja, C. G., et al., 2019,Butterfly transect counts: Manual to monitor butterflies, Report No VS2019.016, Butterfly Conservation Europe and De Vlinderstichting/Dutch Butterfly Conservation, Wageningen, the Netherlands ( accessed 15 April 2021.

Soldaat, L. L., et al., 2017, ‘A Monte Carlo method to account for sampling error in multi-species indicators’,Ecological Indicators81, pp. 340-347.

Tucker, G. M. and Evans, M. I., 1997,Habitats for birds in Europe: a conservation strategy for the wider environment, BirdLife International, Cambridge.

Van Dyck, H., et al., 2009, ‘Declines in common, widespread butterflies in a landscape under intense human use’,Conservation Biology23(4), pp. 957-965 (DOI: 10.1111/j.1523-1739.2009.01175.x).

van Strien, A. J., et al., 2019, ‘Over a century of data reveal more than 80% decline in butterflies in the Netherlands’,Biological Conservation234, pp. 116-122.

van Swaay, C., et al., 2006, ‘Biotope use and trends of European butterflies’,Journal of Insect Conservation10, pp. 189-209.

van Swaay, C. A. M., et al., 2019,The EU butterfly indicator for grassland species: 1990-2017 — Technical report, Butterfly Conservation Europe and ABLE/eBMS ( accessed 15 April 2021.

van Swaay, C. A. M., et al., 2020,Assessing butterflies in Europe — butterfly indicators 1990-2018: technical report, Butterfly Conservation Europe and ABLE/eBMS ( accessed 22 April 2021.

Vickery, J. A., et al., 2009, ‘Arable field margins managed for biodiversity conservation: a review of food resource provision for farmland birds’,Agriculture, Ecosystems and Environment133(1), pp. 1-13 (DOI: 10.1016/j.agee.2009.05.012).

Virkkala, R., 2016, ‘Long-term decline of southern boreal forest birds: consequence of habitat alteration or climate change?’,Biodiversity and Conservation25(1), pp. 151-167 (DOI: 10.1007/s10531-015-1043-0).

Methodology for gap filling

A Monte Carlo method is used to account for sampling error and when not all yearly index numbers for all species are available. The MSI-tool (R-script) is used to calculate Multi Species Indicators and trends in MSIs.

Methodology references

No methodology references available.


Data specifications

EEA data references

  • No datasets have been specified here.

External data references

Data sources in latest figures



Methodology uncertainty

The indicator is accompanied by measures of uncertainty, including smoothed trends and confidence limits (at 95 % level).

Data sets uncertainty

Data on population development of a species are assessed by calculating yearly indices and standard errors using the TRIM software (Pannekoek and Van Strien, 2005,

Rationale uncertainty


a. Common birds

  • Temporal coverage: until the early 1990s, rather few European countries had common bird monitoring schemes in place, which restricts how far back in time representative trends can be calculated.
  • No coherent and structured data breakdown at country level is currently available

b. Butterflies

  • Limited geographical coverage.

Further work

Short term work

Work specified here requires to be completed within 1 year from now.

Long term work

Work specified here will require more than 1 year (from now) to be completed.

General metadata


Indicator code
SEBI 001
CSI 050
Version id: 5

Frequency of updates

Updates are scheduled once per year


DPSIR: State
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
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