H_GRONINGEN - Western marsh harriers (Circus aeruginosus, Accipitridae) breeding in Groningen (the Netherlands) is a bird tracking dataset collected by the Grauwe kiekendief - Kenniscentrum Akkervogels (GKA) / Dutch Montagu’s Harrier Foundation and published by the Research Institute for Nature and Forest (INBO) . It contains animal tracking data collected for the project/study H_GRONINGEN , using trackers developed by the University of Amsterdam Bird Tracking System (UvA-BiTS, http://www.uva-bits.nl ). The study was operational from 2012 until 2018. In total 4 individuals of western marsh harriers ( Circus aeruginosus ) have been tagged in their breeding area in the province Groningen (the Netherlands) close to the Netherlands-Germany border, mainly to study their habitat use and migration behaviour. Data are uploaded from the UvA-BiTS database to Movebank and from there archived on Zenodo (see https://github.com/inbo/bird-tracking ). No new data are expected. See Milotic et al. (2020, https://doi.org/10.3897/zookeys.947.52570 ) for a more detailed description of this dataset. Data in this package are exported from Movebank study H_GRONINGEN - Western marsh harriers (Circus aeruginosus, Accipitridae) breeding in Groningen (the Netherlands) (Movebank Study ID 922263102), which can be viewed at https://www.movebank.org/cms/webapp?gwt_fragment=page=studies,path=study922263102 . Attributes in the data files are defined in the <code>README.txt</code>, in the NERC Vocabulary Server at http://vocab.nerc.ac.uk/collection/MVB and in the Movebank Attribute Dictionary at www.movebank.org/node/2381 . Files README.txt : information regarding the terms of use and data attributes. H_GRONINGEN-reference-data.csv : reference data about the animals, tags and deployments. H_GRONINGEN-gps-yyyy.csv : GPS data recorded by the tags, grouped by year. H_GRONINGEN-acceleration-yyyy.csv : acceleration data recorded by the tags, grouped by year.