This animal tracking dataset is derived from Stienen et al. (2023, https://doi.org/10.5281/zenodo.10209521), a deposit of Movebank study 1258895879. Data have been standardized to Darwin Core using the movepub R package and are downsampled to the first GPS position per hour. The original dataset description follows. DELTATRACK - Herring gulls (Larus argentatus, Laridae) and Lesser black-backed gulls (Larus fuscus, Laridae) breeding at Neeltje Jans (Netherlands) is a bird tracking dataset published by the Research Institute for Nature and Forest (INBO). It contains animal tracking data for the project/study DELTATRACK, using trackers developed by Ornitela (https://www.ornitela.com). The study has been operational since 2020. In total 99 individuals of European herring gull (Larus argentatus) and lesser black-backed gull (Larus fuscus) have been tagged in the breeding colony at Neeltje Jans in the Netherlands, mainly to study their use of offshore waters near the Borssele windpark. Data are automatically synced with Movebank and from there periodically archived on Zenodo (see https://github.com/inbo/bird-tracking). This dataset was collected by the Research Institute for Nature and Forest (INBO), Waardenburg Ecology, Buijs Eco Consult and Deltamilieu Projecten. Funding was provided by the Wozep programme of Rijkswaterstaat on behalf of the Ministry of Economic Affairs of the Netherlands. All datasets from Wozep will be made publicly available, unless stated otherwise.