Abstract
We determined the population density and number of Eurasian Eagle-Owl in one of the regions of Russia (Republic of Mordovia). The work was carried out over sixteen years (2009–2024). The studies were conducted using methods of direction finding of vocalizing birds with subsequent search for nests and with the use of digital voice recorders. The Eurasian Eagle-Owl reliably lives in 16 out of 22 districts (72.7%). During our research, we built more than 60 artificial nests, in which Eurasian Eagle-Owls subsequently settled. In total, during the research period, 89 Eurasian Eagle-Owl habitats (of which 38 in four stationary sites), 125 nesting cases, and 214 chicks were identified. Over the entire period, the birds laid 282 eggs. Productivity for couples was 76%. The most successful years in terms of the number of eggs and chicks in nests were 2014, 2018, 2022, 2023. The density of the Eurasian Eagle-Owl population ranges from 3.1 to 5 pairs per 100 km2. The total population density in the open spaces of the region can reach 583 habitats. The presence of a large number of ravines with stands determines the high population density of Eurasian Eagle-Owl in Mordovia. Making artificial nesting boxes in ravines improves the suitability of breeding sites and promotes better survival of young individuals.