Long-Term Changes in the Number of Birds of the Barguzin Range (Northeastern Baikal Region)

Studies of a 36-year dynamics of the number of bird species (1984-2020) have been carried out on permanent census routes from the shore of Lake Baikal to the Barguzin Range highlands (460-1700 m below sea level). A steady decrease in the total abundance of background bird species after 1997-1998 is revealed. The resulting long-term series (using the example of model groups of birds) makes it possible to identify the responses of the biota to climate change in the Lake Baikal region. Periods of high and low abundance in bird populations are probably associated with wet and dry climate phases. Positive trends of long-term changes in the abundance are found in eight background species (16.0%), and a steady decrease in the abundance is found in 18 species (36.0%). Negative trends in population changes in long-distance migrants prevail over growth trends (11 species against 3 species with positive trends). Some mechanisms of the formation of the local bird population are revealed, including using the redistribution of the nesting species density between the river valleys and habitats at the high-altitude profile. Current long-term climate change in the region has a positive impact on changes in the abundance of background bird species in the highlands when compared with the lower mountain forest belt.