Description 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 from active or new trackers are periodically uploaded from the UvA-BiTS database to Movebank (see https://github.com/inbo/bird-tracking) and then Zenodo, but for this study none of the tracked birds have been observed in the vicinity of their known breeding grounds (and thus data retrieval points) since 2018. 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 README.txt, 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.