Coordinators of national monitoring schemes deliver their national data to the PECBMS coordination unit annually. For information on data and contributing countries see Box Participating countries.
The data delivered are: the national yearly indices per species, the all-sites yearly totals (= the sum of birds counted across all sites per year) and their standard errors, and the covariances between the yearly figures.
Specifically, national coordinators deliver two files per species – so called out and ocv files (see paper by Pannekoek & Van Strien, 2001 or also see website of Statistics Netherlands) – both produced by TRIM when calculating species indices at the national level. These TRIM output files are accompanied by a species list and by comments indicating any potential problems in the data. These comments are taken into account in further data analysis.
National data are checked for their quality using quantitative criteria (see Box Data checks).