Regularities of altitudinal belt differentiation of the summer bird community in the Barguzin Nature Reserve

The research presents the results of investigating the ecological regularities of altitudinal-belt differentiation of the bird population in the Barguzin reserve. Studying the formation of bird fauna and population in the conditions of altitudinal zoning, as well as the factors influencing it, is one of the promising research areas in the Baikal region. The results of such work carried out in undisturbed reference areas can serve as a basis for assessing the size and direction of the natural structure variability of bird communities. The Barguzin State Natural Biosphere Reserve is located in the Northeast Baikal region. It is the oldest Nature Reserve in Russia, created in 1916. Located in undisturbed natural systems, this reserve reflects best global environmental changes. We collected data during expeditions in the summer 2014 on the territory of the reserve within the western slope of the Barguzin Range. The studies were conducted at key sites of the reserve in 5 altitudes: riverside plain (460-520 m asl and higher), foothill (520-630 m asl and higher), forest (630-1200 m asl and higher), subalpine (1200-1400 m asl and higher) and alpine (1400-2800 m asl and higher) in the valleys of three rivers. Ornithological surveys were carried out in the first half of summer, which corresponds to the nesting population of birds. When carrying out the research, we used the method of route counting of birds without limitation of the counting strip width, followed by recalculation to the area in terms of the bird detection range by the interval method (Ravkin Yu.S., 1967). The total length of the routes was 221 km, including the permanent route along the Davsha river valley - 62 km, along the Ezovka river valley - 69 km and the Bolshaya river valley- 90 km. We analyzed the bird population in selected areas using indices of diversity, domination and sustainability of bird communities (Odum Y, 1986; Gashev SN, 2000). We revealed dominant and subdominant species of high altitude belts of the investigated areas. Species whose number was 10% of the total population density of all species of the high-altitude belt were considered dominant (Kuzyakin AP, 1962). In the nomenclature and when compiling lists of birds, we followed L.S Stepanyan (Stepanyan LS, 2003). The names of some species were taken from The List of Birds of the Russian Federation (Koblik EA. et al, 2006). The fauna of nesting bird species was analyzed by their belonging to the faunal groups (Shtegman BK, 1938). The distribution of birds according to the types of food and nesting was carried out taking into account the data presented in the ornithological reports "Birds of the Soviet Union" and "Birds of Siberia". Using cluster analysis, we determined the similarity of the bird community of the high-altitude belts of the Barguzin Range. As a result of the conducted research, we registered 85 species of birds from 9 orders on the territory of the Barguzin Reserve. The main part of the bird population of all high-altitude areas of the reserve is Passeriformes (69% of the total number of species), followed by Charadriiformes (7% of the nesting fauna of the reserve) and Falconiformes (6%). The average density of birds varies from 65 individuals/km² in the alpine belt (the key section of the Davsha River valley) to 242 individuals/km2 in the riverside-flat high-altitude area (the key section of the Bolshaya River) (See Tables 1 and 2). The species diversity of the avifauna of the Barguzin reserve reduces from the foot to the top of the mountains and it is confirmed by the abundance of birds, the parameters of the stability of communities and a complex of information-statistical indices (See Table 3). The overall sustainability of bird communities of the investigated key areas of the reserve takes high values. Bird communities are affected by abiotic and biotic environmental factors. The influence of the heat supply level is clearly traced. A rather low value of the overall stability of bird communities is characteristic of the riverside-flat and alpine high-altitude areas of the Davsha River. The lowest indicator of the overall stability of bird communities is characteristic of the Baikal terraces of the Bolshaya river valley (See Table 3). Probably, the factors that reduce the system stability in the research area can be the radiation balance and moisture conditions. The characteristic of the ecological and faunal structure indicated that the majority of bird species in the reserve belong to the Siberian fauna type (44%), in the trophic bird structure the most widely represented group is insectivorous bird species (45%), and tree nesting birds predominate in researched high-altitude areas during nesting process (35%). The maximum similarity of the avifauna within the Barguzin reserve is observed in the mountain-forest and sub-glacier-subalpine belts, which are distinguished by similar temperature conditions, vegetation composition and the most favorable moistening conditions for birds (See Fig. 1). The paper contains 1 Figure, 3 Tables and 29 References.

Keywords

Authors

References