Abstract
In 2014‒2016 field seasons, bird censuses were conducted on 34 flyways in seven different types of open habitats of the Russian part of the Ishim River region. Ninety-five species from 72 genera from 10 orders were registered. It is established that the taxonomic composition and ecological structure of avifauna of the habitats under investigation comply with their biotopical characteristics; diversity of taxons and ecological groups show positive correlation with habitats’ heterogeneity. In natural habitats, the maximum total abundance of birds, highest species diversity within the habitat (α-diversity) and species sustainability are characteristic of river meadows ornithocenoses, mainly due to low-numbered species and a higher evenness index. In disturbed habitats, the maximum total abundance, species diversity, Shannon diversity index, Pielou’s evenness index, minimal index of diversity and highest indices of elastic and general sustainability are characteristic of abandoned fields ornithocenoses, due to a more complex structure of vegetation communities and habitat resource capacity, which increased in the course of secondary succession. Due to natural and historical unity, middle and northern forest steppe’s avifaunae are most similar. The southern taiga open habitats’ ornithocenoses are most heterogeneous, due to an increased amount of dendrophilous birds along with forest habitats’ increased area and diversity.