The monograph is devoted the bird communities of the ecotone zones in the South of Eastern Siberia. The representations about ecotone territory as to a border between adjacent natural zones and landscapes in taiga and steppe contact are dilated. The South of Eastern Siberia is as model ecotone systems to take. The features of the structure and modern trends of regional ornithofauna changes are revealed. Some questions of the history of formation of the ornithofauna are considered and the possible ways of its heterogeneous structure are proved. The generalisation of the collected materials has allowed to reveal in the Baikal Lake basin a network of the Impotend birds areas, perspective for conservation of a species diversity of birds of the region, and also to develop a recommendations on the protection of vulnerable species of birds.