Based on long-term (1964–2015) research results the characteristics of migrations of Long-tailed Duck Clangula hyemalis (Linnaeus, 1758) are considered and number changes of species on «cold» wintering grounds of Eastern Siberia (predominantly in the headwaters of the Angara River) are shown. For the initial period of observations (1972–1992) rare and non-annual recordings of this species were characteristic though the number of birds registered has a little increased (with 2–5 to 25 individuals) by the end of period. At the second stage (2000–2015) gradual and stable increase of an abundance of a species on wintering grounds is traced. In the same time recordings during vernal and autumn migrations, as well as in former years, are quite accidental and, as a whole, are singular. The possible causes of growth of number of this species on «cold» wintering grounds in Eastern Siberia are considered. One of most change agents is the general warming in the region, reflected on the rate of climatic severity of «cold» wintering grounds. These sites became more comfortable for birds, compared to the end of the 20-th century.