Around fifteen thousand fieldworkers annually count breeding birds using standardized protocols in 30 European countries. The observations are collected by using country-specific and standardized protocols, validated, summarized and finally used for the production of continent-wide annual and long-term indices of population size changes of 170 species. Here, we present the database and provide a detailed summary of the methodology used for fieldwork and calculation of the relative population size change estimates. We also provide a brief overview of how the data are used in research, conservation and policy. We believe this unique database, based on decades of bird monitoring alongside the comprehensive summary of its methodology, will facilitate and encourage further use of the Pan-European Common Bird Monitoring Scheme results. The Pan-European Common Bird Monitoring Scheme database is organised into five datasets: (1) European species indices, (2) European species trends, (3) European species trends for three short periods, (4) a list of details on the national monitoring schemes and (5) a matrix of countries providing data for population size estimates of individual species. Moreover, national-level species indices and uncertainty estimates are also available in the PECBMS database. Due to specific privacy ownership rights, the most recent (2016-2017) data from Spain (10.5281/zenodo.4590140) and Cyprus (10.5281/zenodo.4590189) are under Restricted Access and researchers interested in these most recent updates are required to provide a brief description of the data use. The Austrian and Portuguese datasets are publicly available but researchers using these datasets are kindly requested to notify the national scheme coordinators of their use. A list of regularly updated contacts to all national scheme coordinators is provided at the PECBMS website (https://pecbms.info/country/). We aim to maintain the PECBMS database with annual updates. The annual updates will be available through the PECBMS database deposited at this Zenodo repository to ensure long-term public availability of the data. Updates on data acquisiton and data processing in the dataset released in 2021 are available from: https://pecbms.info/what-is-new-in-2021-data-update/ Updates on data acquisiton and data processing in the dataset released in 2022 are available from: https://pecbms.info/what-is-new-in-2022-data-update/ Updates on data acquisiton and data processing in the dataset released in 2023 are available from: https://pecbms.info/what-is-new-in-2023-data-update/ Updates on data acquisiton and data processing in the dataset released in 2024 are available from: https://pecbms.info/what-is-new-in-2024-data-update/ Updates on data acquisiton and data processing in the dataset released in 2025 are available from: https://pecbms.info/european-wild-bird-indices-2025-update/ Disclaimers (update 2025): PECBMS uses data from separate parts of Germany and Belgium. Therefore, it is possible either to follow the PECBMS division or to contact national scheme coordinators for the official index calculated for the entire country. Germany is divided into Western and Eastern parts in the PECBMS dataset. Contact German national coordinator Sven Trautman (trautmann@dda-web.de) for the indices and trends calculated for the entire Germany. Belgium is divided into Belgium-Wallonia, Belgium-Flanders and Belgium-Brussels in the PECBMS dataset. Contact Belgian national coordinator Antoine Derouax (antoine.derouaux@aves.be) for the indices and trends calculated for the entire Belgium. A regularly updated list of all national scheme coordinators is available on the PECBMs website (https://pecbms.info/country/). Disclaimers (update 2024): Beware the exceptional species with a new start year compared to the original time period. If the new start year equals some of the short trend year, thenew start year is deleted from trends_short (because such trends are in the table trends). The exceptional species and new start trends are 70+90+5820 (new start year 1990 deleted) and 1190+18470 (new start year 2000 deleted). For data updates until 2023, the scientific species names follow the latest HBV-BirdLife checklist released in October 2024, https://datazone.birdlife.org/species/taxonomyChanges are:Bonasa bonasia - Tetrastes bonasiaCyanecula svecica - Luscinia svecicaSylvia undata - Curruca undataSylvia cantillans / Sylvia subalpina - Curruca cantillans / Curruca subalpinaSylvia melanocephala - Curruca melanocephalaSylvia melanothorax - Curruca melanothoraxSylvia hortensis - Curruca hortensisSylvia nisoria - Curruca nisoriaSylvia curruca - Curruca currucaSylvia communis - Curruca communis