EN
In the years 1983 and 1984 inventory of Tawny Owl territories by the mapping method (Domaszewicz et al. 1984a), using vocal stimulation, was carried out on an area of 240 km² (areas Al and A2 in Fig. 1). Additionally data concerning occurrence of Strix aluco on area of 50 km² was obtained from other observers. Wooded areas comprised 7-10%, and built-up areas 50-60% of the total. In the central part of the city (Al = 100 km²) built-up areas covered 70-80%. Census results, literature data and that obtained from informers (Table 1) indicate, that the Tawny Owl was recorded to be permanently in 12 green areas during the last 20-30 years. It disappeared from 9 territories and was found in 19 others, where it was not recorded earlier. During the study period 26-31 pairs (Fig. 1) were recorded within the study area of 290 km² (l pair/10 km²). In the central zone Al the density was 1.2-1.6 pairs/10 km². The total number of population of Strix aluco in Warsaw (485 km²) was estimated to be 40-60 pairs. The data obtained concerning productivity of broods (x̅ = 3.1 juv. per successfull brood) confirm Wenland’s results (1980) who indicated the high number of offsprings of this species brought up in urban conditions.