The paper presents the results of a 5-year study on the population size of the white stork (Ciconia ciconia L.) as one of the indicator species used to assess a biodiversity level in agricultural areas. The study was carried out in Masurian Landscape Park situated in Warmińsko-Mazurskie Voivodeship. The results demonstrated that the white stork population size was closely linked to agricultural areas, in particular, the extensively managed permanent grassland. In the years 2014–2018, even if

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... or changes were observed in the land use structure, the white stork population size showed a slight upward trend within the study area. In order to maintain this status, efforts should be made to preserve open landscapes (first and foremost – meadows and pastures), which are preferred feeding grounds of white stork. Consequently, potential decision as regards afforestation and housing should be made considerately.