The Eagle Owl is one of the rarest owls inhabiting Poland and despite a relatively good recognition of its distribution, there is lack of information about its population size in many refuges. The Białowieża Primeval Forest has long been known as a place of the Eagle Owl occurrence; however, no comprehensive assessment of its population size has been carried out there so far. The census of the Eagle Owl, conducted in 2017, was based on both bird listening in observation points and active search for the presence of the species traces. The results of the study indicate the possibility of nesting from 3 to 7 pairs of the Eagle Owl in the Polish part of the Białowieża Primeval Forest. Most of the territories inhabited by the studied species are located in the Białowieża Forest Districts and one in the Białowieża National Park. Presumably, the low density of the Eagle Owl in the Polish part of the Białowieża Primeval Forest is due to the lack of suitable feeding habitats.
Summer diets of two sympatric raptors Upland Buzzards (Buteo hemilasius Temminck et Schlegel) and Eurasian Eagle Owls (Bubo bubo L. subsp. Hemachalana Hume) were studied in an alpine meadow (3250 m a.s.l.) on Qinghai- Tibet Plateau, China. Root voles Microtus oeconomus Pallas, plateau pikas Ochotona curzoniae Hodgson, Gansu pikas O. cansus Lyon and plateau zokors Myospalax baileyi Thomas were the main diet components of Upland Buzzards as identified through the pellets analysis with the frequency of 57, 20, 19 and 4%, respectively. The four rodent species also were the main diet components of Eurasian Eagle Owls basing on the pellets and prey leftovers analysis with the frequency of 53, 26, 13 and 5%, respectively. The food niche breadth indexes of Upland Buzzards and Eurasian Eagle Owls were 1.60 and 1.77 respectively (higher value of the index means the food niche of the raptor is broader), and the diet overlap index of the two raptors was larger (Cue = 0.90) (the index range from 0 – no overlap – to 1 – complete overlap). It means that the diets of Upland Buzzards and Eurasian Eagle Owls were similar (Two Related Samples Test, Z = –0.752, P = 0.452). The classical resource partitioning theory can not explain the coexistence of Upland Buzzards and Eurasian Eagle Owls in alpine meadows of Qinghai-Tibet Plateau. However, differences in body size, predation mode and activity rhythm between Upland Buzzards and Eurasian Eagle Owls may explain the coexistence of these two sympatric raptors.