On the basis of many years of research (1972-2019), the peculiarities of the formation of “cold” wintering of near-water and waterfowl in the source and upper reaches of the Angara river are considered. Despite the fact that it has been for a very long time studied, this issue has not yet received proper coverage in the scientific literature. Until now, there are different opinions about the reasons for its formation - sometimes very controversial, which requires a more complete analysis of the available materials. We found out that the formation of wintering is associated with delays in the departure of birds that have not accumulated a sufficient amount of plastic substances necessary for the continuation of migration. Late freezing source and upper course of the Angara river (mid-January - early February) allow birds to stay for a long time. Here, due to the huge mass of water heated in summer, which increases the temperature of the surface air layer in the late autumn and early winter periods, a thermal is refugium formed. However, by the time the birds are able to continue their migration, it becomes impossible. Permanent snow cover and very low air temperatures are in the surrounding areas established, and all lake systems freeze. This thermal refugium, into which birds, delayed with flight, gradually move, becomes an ecological trap, and the “cold” wintering itself is forced.

On the basis of many years of work by ornithologists covering the entire second half of the past and the beginning of the current century, the features of the dynamics of the bird fauna of Inner Asia as a result of climate warming are considered. The central position of Eastern Siberia caused its stronger warming, which makes it possible to consider in detail various aspects of this process. Severe droughts, followed by long dry periods, observed in the arid regions of Central Asia in the second half of the 20th century, caused massive migrations of birds to the north. Strong changes in habitats were found in birds using intrazonal wetlands ecosystems for nesting. Native steppe and desert birds inhabited areas within their natural zone. They are characterized by occasional flights to the northern boundaries of their ranges towards the end of the second half of the study period. As a result of mass evictions, the diversity of birds in Eastern Siberia increased by 22.6% (110 species), but their abundance remained almost at the initial level. At present, the number of coastal birds in the south of Eastern Siberia, as well as in Central Asia, has greatly decreased, as a result of a shift in the optimum range to the north.

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