Pleistocene gaps in the areas of birds of Eastern Siberia and their filling in the modern period of climate warming

Abstract

Based on long-term studies (1968-2022), materials are presented on the change in the areas of birds in Eastern Siberia, caused by pronounced climate warming in the second half of the 20th - early 21st centuries. During the period of the last strong Pleistocene cooling, this territory was characterized by mountain-valley icing. As a result, the common areas of many bird species were torn apart. Subsequently, in isolated groups, evolution followed different paths, which led to the emergence of new closely related species. At present, due to the strong warming of the climate in Eastern Siberia (1.9°/100 years on average) and the change in the area boundaries of many bird species, the former gaps in their areas are being filled. For many bird species, secondary contact has been recorded with the formation of vast transitional zones in which their areas overlap to some extent. So far, there are relatively few of them, but the general trend towards overlapping areas of a number of bird species can be seen quite clearly. Among the species with area gaps without further speciation, shorebirds sharply predominate. However, among the species whose area gap ended in speciation, their number is significantly reduced. The current period of sharp climate warming and a significant change in the areas of birds in Eastern Siberia is characterized by a sharp increase in their biodiversity. However, it is combined with the low population density of many species, especially those new to the ecosystems of the region. Such a situation requires increased attention to the existing structure of the bird population and its dynamics, since it is observed extremely rarely - the shortest duration of the known centuries-old climate cycle is about 2000 years.