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.

New TRIM – TRIM in R

New version of the programme TRIM which was rebuilt as a package for the freely available and widely used open source statistical program R.

RTRIM contains the same methods and models for nature monitoring data as the original versions of TRIM. It can still work with the same input data and produces exactly the same output data, but as a package in R it can easily be integrated in other R programming processes. As a result of this there is a wider choice in how input data is provided, in how options and settings are chosen and how and what output is provided. New in this version is also the in-built possibility to combine results from other TRIM runs, e.g. to combine results obtained from the analysis of regions of a country into a single new output with a combined trend, indices and standard errors.

Being developed as R-package TRIM is as good as new and is made available for further developments by the large R-society. A development Statistics Netherlands is already working on, is making TRIM suitable for the use of multiple data per year (such as monthly counts). The renewed TRIM is available as RTRIM package on CRAN (Comprehensive R Archive Network).

Users of BirdStats cannot yet use this in combination with RTRIM, but we are working on a solution for that too.

Manual, documentation and helpfiles in the R environment with several programming examples can be found on the CRAN website. For any questions about the use of RTRIM, please contact

Also, RTRIM shell documents have been developed by Statistics Netherlands, which provides calculation and outputs of national species indices in a standardized way. Using this shell makes it easier to process large batches of species with specific model parameters at once. The shell is a combination of several R scripts together with a short user guide and can be downloaded here. Note that the use of covariates in the models is not yet included in this new development, but will be in the future.

See more info about TRIM also on the website of the Statistics Netherlands

Old TRIM – TRIM in Delphi

Old version of the programme TRIM was originally developed some 25 years ago by Statistics Netherlands (Pannekoek and Van Strien, 1991) and was made available as a freeware stand-alone program. The program has had several updates since then, however, the original programming language (Delphi) has become outdated and rendered further developments.

The latest version is TRIM 3.54 (released in 2006) which is designed to run under 32-bits versions of Windows, as Windows98, Windows2000 and WindowsXP.

Warranty Disclaimer. This software and the accompanying documentation is provided “as is”. Statistics Netherlands disclaims all warranties, either expressed or implied.

TRIM can be downloaded from the EBCC website together with a manual, a powerpoint presentation explaining TRIM for first users, and papers using the TRIM method. Alternatively, you can download TRIM as a part of the program BirdSTATs which enables to calculate indices and trends in batch mode to perform the statistical analysis for series of bird counts in the dataset.