Waterfowl and Shorebirds: Formation and evolution of “cold” wintering grounds in Inner Asia (Baikal Siberia)

Abstract

Despite the widespread occurrence of “cold” wintering of waterfowl, the causes of their formation have been studied very poorly. Very harsh winter conditions are typical for Eastern Siberia, but wintering grounds with a high number of 55.0-60.0 thousand birds are also formed here. Such wintering grounds include the source and upper course of the Angara River (thermal refugium). The high death rate of nests in the summer due to the unstable mountain floodplain water regime of the rivers of the region is compensated by the repeated nesting of birds. As a result, their total breeding season is greatly increased. By the time of migration, the late broods do not have time to accumulate enough plastic substances (fat) necessary for migration to the southern wintering grounds. Favorable conditions at the beginning of winter in thermal refugiums contribute to long delays of birds in feeding and resting places. However, by the time they are able to continue migration, it becomes impossible. Snow falls in the adjacent territories, reservoirs are covered with ice and a constant negative air temperature is established. Consequently, the “cold” wintering of shorebirds and waterfowl is forced. The basis of their species composition is formed by the animal-eating diving duck species. In this regard, their protection and maintenance of numbers in extreme years are difficult and expensive tasks.