The ABV (Common Breeding Birds in Flanders) project is based on a monitoring network developed by INBO’s BMK (Biometrics and Quality Assurance) service, and consisting of 1200 random stratified kilometre grid squares throughout Flanders. INBO is responsible for the coordination of the project and for reporting to regional, national and international authorities, while Natuurpunt is responsible for coordinating the volunteer network and distributing the sampling grid squares among these volunteers. Every year, the project delivers indices for about 100 general and scarce breeding birds in Flanders.