Ecology of Eurasian Bittern (Botaurus Stellaris) in the Ryazan Region, European Russia

The natural history of the Eurasian Bittern (Botaurus stellaris) was studied in the Ryazan Region in 19812024 when the species was common widespread. During the dry seasons of 2015, 2019 and 2020, the number of great bitterns decreased significantly. The main habitats are thickets of coastal aquatic vegetation - Phragmites sp., Typha angustifolia, T. latifolia, Schoenoplectus lacustris and some other plants. First birds within the region arrive from March 23 to April 29, on average - April 14. The start of reproduction was noted from April 26 to June 19; first eggs in most nests were laid during May. A complete clutch consists of 3-6 eggs, on average 4.7 ± 0.78 (n = 33), brood consists of 2-5 chicks, on average 4.2 ± 0.90 (n = 17). Both survival of nests till fledging (81.8%) and breeding success expressed as the proportion of chicks that left their nests relative to the total number of laid eggs (70.5%) were high. Birds leave their breeding area during September and October, with November 3, 1963 being the latest date of the species observation.