<p>The article presents the materials of long-term studies of the ornithofauna of the floodplain of the middle reaches of the Zgar River within the limits of the zoological reserve of the national significance of "Zgarsky", located within the limits of the Litinsky and Zhmerinsky regions of the Vinnytsia oblaast. The study of the species structure, the nature of topical bonds, and the ecological groups of the avifauna, revealed the peculiarities of the dynamics of the population density of the bird sanctuary in the main types of biotopes during 2005-2017. The territory's avifauna structure comprises 169 species of birds, of which 86 species are nesting and migratory, 38 - settled, 31 – on passage, 12 - wintering, 2 – nomadic. The dominant species of bird communities were obligatory and optional zoophages (124 species), some fewer were phytophagous (38 species) and polyphagous (7 species). The trends in quantitative indices of the ornithofauna demonstrates the tendency to increase the role of dendrophiles species in the formation of nesting bird communities of all the habitats, including meadow and wetlands. We also registered that the ratio of camphoric species in meadow bird communities is decreased. This occurs due to the backdrop of reduced man-caused load and acceleration of natural successional processes, which are accompanied by overgrown shrub-tree phyto-associations of most habitats. The highest indexes of species similarity in the reproductive period are typical for the "Upper" and flooded peat quarries (Cj = 0,565), as well as flooded quarries and meadows (Cj = 0,301). In the latter case, the similarity is determined by common dendrophile species, which may indicate degradation of meadow bird communities. The floodplain of the middle reaches of the Zgar River inhabits 16 species of birds included in the Red Data Book of Ukraine, of which 7 were the nesting species or regularly registered in breeding period.</p>