| Summary: | Present work is based on the original materials collected during the field investigations in the area of lower reaches of Sula River (Cherkasy and Poltava regions of Ukraine) in 1979 – 1992 and 2009 – 2010. Researches were being carried out during the whole year, so all the most important periods of the birds’ life (seasonal migrations, nesting and wintering) were under attention.In the article the results of multiyear study of 30 rare and threatened birds’ species of the region are presented. Osprey, Black Kite, White-tailed Eagle, Peregrine, Corncrake etc. are among them. Every description together with information about biology and dynamics of the species quantity includes a definition of its conservation status.Comparative analysis of the state of some species on the different stages of the avifauna formation in the Sula Bay of the Kremenchuh water reservoir was carried out. For some nesting species the reasons of their changes in number or disappearance were found out. Researches showed that the most significant influence on the rare and threatened component of avifauna had a worsening of conditions for nesting in the region and declining a trophic capacity of habitats which were caused both by the natural processes (successions) and by the changes in the economic use of the Sula Bay. In particular, a negative influence on some nesting and migratory species of the processes of swamping and overgrowing of shallow zones with high aquatic vegetation was ascertained. It was agreed that stoppage of the haying and the cattle pasturing on the islands worsens the conditions for breeding of majority of species nesting on ground (waders, gulls and others). Despite this, the region of lower reaches of Sula River undoubtedly continues to remain exclusively important place for support to diversity of not numerous, rare and threatened species of birds in the different seasons of year.
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