TRIM (TRends and Indices for Monitoring data) is a program used to determine species‘ population trends. It allows for missing counts using estimation, and yields yearly indices and standard errors using Poisson regression. TRIM is a freeware program developed by Statistics Netherlands in the framework of wildlife statistics. Read more.


BirdSTATs (The Species Trends Analysis Tool for birds) is an open source Microsoft Access database for the preparation and statistical analysis of bird counts data in a standardised way. The BirdSTATs tool is programmed to use and automatically run the program TRIM (TRends and Indices for Monitoring data) in batch mode to perform the statistical analysis for series of bird counts in the dataset. In this way it is suitable for use in all European countries participating in the Pan European Common Bird Monitoring Scheme (PECBMS). Using the BirdSTATs tool results in standardised indices that are used as subsets by the PECBMS for the calculation of overarching European wild bird indicators. Read more.

Updated version of the BirdSTATs (including TRIM 3.54) which was released in March 2016 can be downloaded here (3.2 MB).


The software and further information to undertake these analyses are freely available at:

Distance sampling takes account of the fact that the number of birds seen or heard declines with distance from the observer. The shape of this decline, the distance function, differs among species, among observers and, importantly, among habitats. Distance sampling models the ‘distance function’ and estimates density taking into account both the birds that were observed, plus those that were present but not detected.

More advanced software

More advanced software, such as the programs MARK, BROWNIE, CAPTURE, ESTIMATE, OREMARK, RELEASE and radio-tracking programs are available at the page of professor Gary C. White, Colorado State University.