Cold wintering of coastal birds in the source and upper reaches of the Angara river: Changes in abundance and species structure in the conditions of a sharp climate warming

Abstract

Based on long-term research (1972-2023) and analysis of literature data, materials on the dynamics of the number and species structure of wintering shorebirds and waterfowl on cold wintering in the source and upper reaches of the Angara River (up to the town of Usolye-Sibirskoye) are presented. This is the largest cold wintering of coastal birds in Eastern Siberia – up to 55.0-60.0 thousand birds, the formation of which is due to very specific conditions of the upper reaches of the Angara River. This is the thermal refugium of the Upper Angara region, which ensures the accumulation of birds at the end of migration in more favorable areas of this region. It is divided into two sections: the first stretches from the source of the Angara River to the village of Taltsy, the second from the Irkutsk hydroelectric dam to the town of Usolye-Sibirskoye, and in warm winters slightly below it. On the basis of special works on the study of the dynamics of the number and species structure of birds, special methods have been developed: accounting on ice holes, accounting during the evening flight of birds to the lake Baikal (during cold periods) and accounting using a hovercraft (SVP) (during periods of severe climate warming). The basis of wintering birds is the Goldeneye Bucephala clangula (from 95.0% to 98.5% of their total species structure). However, the structure of secondary species can increase dramatically and we have noted new species that have never been found here before. The collected materials allow us to understand the reasons that determine the dynamics of the number and species structure of coastal birds in the “cold” wintering grounds of Inner Asia in the conditions of a sharp warming of the climate