Understanding EBBA2 50-km distribution maps

Yes, they all show exactly the same set of squares for each species. They just differ in the type of information provided, occurrence, breeding evidence and abundance, respectively.

50-km occurrence maps simply show the presence or absence of the species in a given square according to field observations either in the EBBA2 period (mainly 2013–17) or EBBA1 period (mainly 1980s). Presence data refer to either possible, probable or confirmed breeders (see next question).

Birds are mobile species and can be observed far from the areas where they reproduce, e.g. as visitors during migration or post-breeding dispersal. 50-km breeding evidence maps show the maximum observed likelihood that the species breeds in every square. Three standardised categories are used to determine this likelihood: possible, probable or confirmed breeder. These categories are based on the type of observation done in the field, which is standardised in 16 atlas codes.

Abundance is a key parameter to complement the distribution of bird occurrence and breeding likelihood, and as such is widely used in research and conservation. Abundance maps show the information on the number of breeding pairs per square reported by national coordinators. Depending on the characteristics of the species and the available data, three main approaches were essentially used to collect these data, namely direct counts, statistical inference and expert assessment. The first was mainly used for scarce but conspicuous species for which counts were available, the second was often used for widespread and common species, and the third if other methods were not possible.

Breeding evidence maps show the highest category reported by any of the countries. For abundance the information from the countries concerned was pooled.

Understanding the EBBA2 10-km modelled maps

Modelled maps show patterns of probability of breeding occurrence in Europe at 10-km resolution. These maps should be mainly interpreted at European scale and treated with caution at more restricted spatial levels, where other, local sources of information are likely to be more reliable. Despite these limitations, EBBA2 modelled maps very likely represent the best maps of breeding occurrence ever developed for Europe as a whole, and also for many parts of the continent where information at this level of detail has not been available so far.

Modelled maps show relative rather than absolute values of probability, so values can be compared within a single map but not necessarily between modelled maps of different species. Patterns of occurrence are better compared between species by means of the 50-km abundance maps (although the details of the modelled map are lost).

Abundance maps show estimations of the number of breeding pairs per 50-km square, and modelled maps show probability of occurrence per 10-km square. For many species, in particular widespread passerines, modelled maps can be interpreted as gradients of relative abundance. This is why the geographical patterns of abundance maps and modelled maps are often similar. However, some caution is required here, because probability of occurrence may remain constant above certain thresholds of abundance. On the other hand, modelled maps may not reflect abundance well, e.g. for species with a clumped occurrence. Finally, it should be taken into account that modelled maps were generated for the whole of Europe at once, while values in the abundance maps were provided country by country.

Understanding the EBBA1-EBBA2 change maps

No. EBBA2 change maps only show changes in the species presence between the two atlases. They basically show squares where the species was found in one or the other atlas, or in both.

Overlaying the maps of EBBA1 and EBBA2 can give you a rough idea about change but we do not advise you to make these comparisons, because important information regarding the quality of the data will be lacking. Please use the change maps instead, for which the data have been controlled for effort in data collection.

Change maps are restricted to the continuous geographical area that was well covered in both atlas periods. Since the coverage was far more complete in EBBA2 than in EBBA1, this means that the area analysed in change maps includes areas homogeneously covered in EBBA1. Thus, Cyprus, the Asian part of Turkey, the Canary Islands, most of the European parts of Russia and Kazakhstan, Georgia, Armenia and Azerbaijan were excluded from the change maps.

Not exactly. Although the basis of the change map are the data from these two atlases, the squares used for the comparison and the calculation of the change index are a subset of the total number of surveyed squares. The set of squares selected for its inclusion in the change maps are those that we consider that better approach the real changes on species occurrence within the 30-year study period. Information on completeness of coverage, species richness plus a few less important criteria were used to determine the set of squares qualifying for robust comparison between the two atlases. We recommend the use of the data underlying the change maps for further analyses of change in species occurrence. See further information in the Methodology and the book.

Change maps give an impression of the spatial pattern of gains and losses in the distribution of a species but do not show the magnitude of change. We quantified the change in distribution by calculating a change index as: Change index = 100 * (N2–N1)/(N2+N1), where N1 and N2 are the number of occupied squares for a given species in the EBBA1 and EBBA2 periods, respectively. Positive and negative values of the change index indicate the extent to which distribution has increased or decreased: 0 indicates no change, –100 extinction and +100 colonisation. This index has the advantage of keeping increases and decreases symmetrical in magnitude, which facilitates comparisons between species. However, the index should not be interpreted as a percentage change from a past reference. See further information in the Methodology and the book.

Not a straightforward manner. At large scales such as Europe, distribution expansions are often related (actually favoured) to population increases. And the opposite is also often true, i.e. distribution shrinking is linked to an overall population loss. However, this is not always the case. In some cases distribution and population size can change in a divergent manner. For example, this happens when a species becomes concentrated in particular areas in which habitat quality has increased over time. For changes in population size please consult trends reported by the PECBMS project and European Red List of Birds.

Atlas work is not an easy task and it takes years (10 in the case of EBBA2) to accomplish such a huge project. A total of 30 years have passed between the EBBA1 and EBBA2 fieldwork periods. However, the EBCC is fully conscious of the interest of potential updates in the near future.

How to get/use/contribute

Yes, all maps can be downloaded directly from the map viewer (not through data request) and used under the following Creative Common license. Please do not crop the source information which is shown on the maps.

However, any commercial use of atlas maps or information will have to be preceded by a data request to EBCC. Downloaded maps are in png format and show the source information (EBBA2 project), with either Creative Common License (50-km occurrence maps) or EBCC copyright (the rest of maps) being prominently indicated.

Downloaded maps include a short information on the source. Do not remove this information. When you use maps and data in publications (scientific publications, reports, online publications) EBBA2 should always be cited using both the website and the original book citations:

EBBA2 website citation

EBCC (2022). European Breeding Bird Atlas 2 website. European Bird Census Council. Accessed from: http://ebba2.info (Day/Month/Year).

EBBA2 book citation

Keller, V., Herrando, S., Voříšek, P., Franch, M., Kipson, M., Milanesi, P., Martí, D., Anton, M., Klvaňová, A., Kalyakin, M.V., Bauer, H.-G. & Foppen, R.P.B. (2020). European Breeding Bird Atlas 2: Distribution, Abundance and Change. European Bird Census Council & Lynx Edicions, Barcelona.

Data from EBBA2 and EBBA2 are available for further analyses following the data access policy agreed by the EBCC network of national coordinators. Please consult the data access page for further information. 50-km occurrence data for all species and for all of the EBBA2 study area are open access under a Creative Commons License. For the other types of data, the EBCC retains the copyright and a request should be done. Data are downloaded in csv format.

No. Illustration copyright belongs to the artists, not to the EBCC, which has only the right to use them for the publication of EBBA2 results.

Yes. The EBCC partner organisations usually base their atlas and monitoring work on the contribution of volunteer ornithologists. Please contact national coordinators in your country to find out the best possible manner to participate in bird atlas and monitoring projects.

Yes, donations to support the EBCC activities are welcome. The vast majority of funding to keep bird monitoring projects in Europe running currently lies on the shoulders of the thousands of volunteer fieldworkers and the coordinators in the EBCC network and on the efforts done by organisations at national level. In many countries these projects lack adequate funding. You can contribute to improving this situation with voluntary contributions to the EBCC. Please consider this to help bird monitoring programmes running in Europe and contact us to discuss how this could be made and how this would be recognised.


Maps, either at species or multispecies levels, often need additional information for correct interpretation. Such information can be found in the species accounts and the general chapters of the EBBA2 book.

Yes. You may request advice by the EBCC, which will be happy to provide it, if capacities allow. For a general overview on the use of EBBA1 data for research, you may consult a manuscript that analysed it.

No. The EBBA1 and EBBA2 projects studied distribution in the breeding season, which is basically spring and early summer for most of European birds, but can extend also to winter and autumn in very particular cases. The EuroBirdPortal (EBP) project collects information on species occurrence in the non-breeding period as well. Several countries have also produced year-round, wintering or migration atlases.

The EBCC is responsible for the information for birds only. Similar projects are running for other taxa, such as the 2nd European Mammal Atlas (EMMA2), or an atlas for amphibians and reptiles.

Although EBBA2 data may be useful at continental scale, the detail of the information usually needed for environmental impact assessments often needs local data. We recommend to check availability of national atlas data first. National atlases were often produced in parallel with EBBA2, but often at finer scale, therefore may be better for specialised targeted studies. If EBBA2 data seem the most appropriate, the data access rules apply.

EBBA2 was based on the data provided by national partners from 48 European countries. You can find information on who provided the data in your country in Organization.

If you have questions on the information in particular squares or countries, please contact the national coordinators.

We are grateful for information on errors in the EBBA2 maps. Please note that the maps only refer to evidence from the time period covered in the atlas. A species may have bred a few years before or after this period, in which case it is not shown on the map. We also advise you to consult the texts in the EBBA2 book before reporting suspected errors.

Please contact us and report the error. We will fix it as soon as possible. Despite we do everything possible to check whether the links at the web site are up to date, it could happen that the links change and we don’t notice it. Reporting the error will be very helpful to us and other users of the web site.