The history of avifauna of the South of Eastern Europe during the last 48 Ma was traced by the results of determination of fossil bird remains and taxonomic revision. In total, four main paleoecological stages were allocated for the studied region: middle Eocene stage (47,8-41,2 Ma); Oligocene - middle Miocene stage (41,2-11,0 Ma); late Neogene stage (11,0-1,81 Ma); Quaternary stage (1,81 Ma-our time). The version of palaeoecological scale was proposed for the Eocene-Holocene paleoecosystems of the South of Eastern Europe.
It has been observed that during middle Eocene the studied territory consisted of islands in the epicontinental sea. The climate at that time was warm, terrestrial mammals were probably absent, thus top levels of the trophic pyramid was occupied by birds of different ecological specialization. The islands were overgrown with wooden vegetation: paratropical forests without expressed seasonality. During Oligocene, as the result of marine transgression, terrestrial ecosystems were submerged.
Terrestrial ecosystems, whose species diversity is independent of earlier avifaunas, have emerged in the South of Eastern Europe during late Neogene (ca. 11,0 Ma). At least four great subsequent changes of palaeoecological conditions occurred at that time. It was displayed in consistency of avifaunal assemblages: 1) 11,0-9,8 Ma, 2) 9,8-8,2 Ma, 3) 8,2-4,2 Ma and 4) 4,2-1,81 Ma. The climate was dry between 8,2-7,1 Ma, and between 1,8-0,52 Ma. During the period of 7,1-1,8 Ma, the climate was more humid, however it became slightly drier between 4,2-3,6 Ma. The rotation of avifaunas occurred in the periods of decreasing humidity which points to impact of aridification on changes in faunal composition.
It was found that recent avifauna of the South of Eastern Europe had begun to emerge during early Pleistocene, nearly 1,81 Ma. The main factors of this process were: 1) changes in temperature and humidity leading to increase the geographical ranges of birds (except for Willow ptarmigan (Lagopus lagopus), Grey partridge (Perdix perdix) and Great bustard (Otis tarda)); 2) changes in sea level and catchment area of rivers. Impact of changes in sea area are more ambivalent than temperature influence. Marine transgression has contributed to increasing the number of piscivorous birds and decreasing the number of birds nesting in the islands. Marine regression contributes to opposite process. The influence of inter-species competition on number of bird species was not observed.
The obtained data show positive correlation for the trends in number within five groups of bird species during the Holocene: 1) ducks; 2) species of dry landscape with cool or temperate climate; 3) birds nesting on islands; 4) piscivorous birds; 5) synanthropic species.
Increasing of the area of forest ecosystems at the stage of seral community has taken place at the end of Pleistocene. That happened in three main ways: from Carpathian Mountains, from Central Russian Upland and from Crimean Mountains. Nearly 8,4 – 4,6 Ka forest ecosystems of this type have spread southwards to 49,6° north latitude. Later, the southern edge of these forests has been reduced. Forest ecosystems at the climax stage were distributed on the north part of the modern territory of Ukraine ca. 4,6 Ka. Their area declined nearly 2,4 Ka, however began to increase 1,0 – 0,7 Ka. During the little Ice Age, 0,7 – 0,1 Ka, forest ecosystems at the climax stage have prevailed over those at the stage of seral community. Obtained data are agreed with climax pattern theory after R. H. Whittaker and are contrary with other climax theories.
The study has also found that numbers of certain species recently involving into the Red Data Book of Ukraine were higher during the Holocene than nowadays: Dalmatian pelican (Pelecanus crispus), Gadwall (Anas strepera), Ferruginous duck (Aythya nyroca), Red-crested pochard (Netta rufina), Common goldeneye (Bucephala clangula), Ruddy shelduck (Tadorna ferruginea), White-tailed eagle (Haliaeetus albicilla), Common crane (Grus grus). The numbers of such species as Pygmy cormorant (Phalacrocorax pygmaeus), European shag (Phalacrocorax aristotelis), Lesser white-fronted goose (Anser erythropus) and Demoiselle crane (Anthropoides virgo) was considerably less than numbers of closely related species throughout the Holocene. The numbers of Great bustard (Otis tarda) at the territory of the South of Eastern Europe was fluctuating in a wide range: increasing in arid periods and decreasing in warm, humid phase of the Holocene. The numbers of Red-breasted goose (Branta ruficollis) was increased in warm phase of the Holocene.
