Spatial-typological structure and organization of the bird population of the Prealtai plain in the second half of the summer

The paper presents information on the spatial heterogeneity of the bird population of the Prealtay plain in the second half of the summer. We compiled the classification and the spatial-typological structure of the ornithocomplexe heterogeneity and assessed the strength of the connection between environmental factors and heterogeneity of communities. We conducted bird counting in 2003-2005 and from 2014 to 2016 at four key sections of the Prealtai plain. The first section was located in the eastern part of the Prealtay plain within moderately moist meadow-steppe and forest-steppe landscapes, and the second site included the residential habitats of Biysk (Biysk and Krasnogorsk districts of Altai Krai). The third and fourth key sections were located in the central and western part of the Prealtay plain within arid and the moderately arid steppe landscapes (Petropavlovsk and Kur'inskiy districts of Altai Krai). 42 variants of bird population were analyzed and 158 species were counted for all years. Birds were counted on permanent routes, without limitation of the transect width. The recalculation for the area was conducted over average detection distances (Ravkin, 1967). The total length of the main registration routes was 795 km. The results of all bird counts are given as the number of individuals per 1 km2. We classified the bird population using one of the methods of cluster analysis (factor classification) (Trofimov, Ravkin, 1980). All the considered variants of ornithocomplexes were divided into an unspecified number of groups according to the degree of similarity of each sample with all the others. The Jacquard coefficient was used as a measure of similarity (Jaccard, 1902; Naumov, 1964). The spatial-typological structure was constructed on the matrix of average coefficients of similarity at the level of the bird community subtype. In the second half of the summer, the maximum total abundance of birds was recorded in built-up habitats (1793-1873 individuals per km³). The number of birds was 1.7 times less in floodplain meadows with bushes, and also in wet meadows outside the floodplain with coppices and in lowland swamps (1103). There were 3-3.5 times fewer birds in field, meadow-steppe and forest ornithocomplexes (505-599). More than five times fewer birds were in stubble fields of forage grasses and meadow-pastures adjoining them (322), and the minimum was observed in fallow lands (84). In the group of aquatic communities, the greatest number of birds was on small rivers with open banks (1284-1607), and significantly fewer were with increasing bushiness of banks and watercourse areas (140-409). The greatest number of species was noted in the subtype of floodplain meadows with shrubs, wet meadows outside the floodplain with coppices and lowland swamps (105/64), which is due to high patchiness of habitats, moistening, bushiness and food capacity. A decrease in the total number of encountered and background species was observed in forest and residential ornithocomplexes (71/46 and 72/32). In residential ornithocomplexes, the total number of species is the highest in the areas of urban multi-storey buildings, industrial zones and settlements (69/31) and much less in urban one-storey buildings and gardens (23/20). Then, the species richness decreases in the ornithocomplexes of fields, steppe meadows and meadow steppes (55/29), in stubble fields of forage grasses (34/24), in feather-grass steppes (19/15) and in fallow lands (9/7), that is, as plowing, grazing, haymaking and steppification increase. In aquatic communities, the species richness of birds is the highest in the population subtype of large and medium-sized rivers (32/16), and also on small rivers with open pebble-silt banks (21/19). With an increase in bank bushiness and, correspondingly, with a decrease in the food availability for birds, the number of species reduces (10/9). In the spatial-typological structure of the bird population, we examined subtype groups: undeveloped and build-up areas and aquatic communities. On the structural graph, the main trends in the change in the bird population are associated with afforestation, moistening, plowing, degree of development, haymaking, watering, watercourse size and the nature of small river banks (See Fig.). In forest habitats, the willow tit (Parus montanus Conrad von Baldenstein, 1827), the great tit (Parus major Linnaeus, 1758) and the chaffinch (Fringilla coelebs Linnaeus, 1758) prevail. With a decrease in afforestation and an increase in habitat patchiness and bushiness, the blyth's reed-warbler (Acrocephalus dumetorum Blyth, 1849), the common whitethroat (Sylvia communis Latham, 1787) and the black-crowned goldfinch (Carduelis carduelis Linnaeus, 1758) appear among the dominants, and as plowing and steppification increase, inhabitants of open spaces (the Eurasian skylark (Alauda arvensis Linnaeus, 1758), the Siberian stonechat (Saxicola maurus Pallas, 1773) and the booted warbler (Iduna caligata Lichtenstein, 1823)) begin to dominate. Under the influence of haymaking on fields of forage grasses and reduction in productivity in fallow lands, the population density of birds decreases two and seven times, respectively, in comparison with other field communities. Besides the Eurasian skylark, in the ornithocomplexes of stubble fields of forage grasses, the rook (Corvus frugilegus Linnaeus, 1758) and the Richard's pipit (Anthus richardi Vieillot, 1818) prevail, and in fallow lands it is the collared sand martin (Riparia riparia Linnaeus, 1758) and the common raven (Corvus corax Linnaeus, 1758). An increase in the total abundance of birds with the expansion of built-up areas and anthropogenic food capacity is mainly determined by synanthropic species, i.e. the house sparrow (Passer domesticus Linnaeus, 1758), the Eurasian tree sparrow (Passer montanus Linnaeus, 1758) and the rock pigeon (Columba livia J.F. Gmelin, 1789). Thus, the highest bird population density on the Prealtay plain was recorded mainly in residential habitats. Within undeveloped territories, an increase in the total abundance of birds correlates mainly with the growth of moistening and habitat patchiness and bushiness. The heterogeneity of bird population in the second half of the summer mostly depends on anthropogenic factors (64%), primarily on the degree of development (60%) and plowing (18%) (See Table). To a lesser extent, the heterogeneity of bird distribution depends on food capacity of the habitats (34%). The impact of forest-forming species composition, afforestation, moistening and bushiness is much less significant (12-20%). Thus, on the Prealtay plain the territorial heterogeneity of the bird population depends more on anthropogenic factors than on natural ones. This is due to a much smaller area of forests, arid climate and widespread agricultural and residential landscape degradation. The paper contains 1 Figure, 1 Table and 38 References. Acknowledgments: We are sincerely grateful to Professor YuS Ravkin, Dr. Sci. (Biol.) (Institute of Animal Systematics and Ecology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk) for comments and editing of the manuscript, as well IN Bogomolova and MI Lyalina (Institute of Animal Systematics and Ecology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk) for help with calculations. We express our special gratitude to AA Odintseva, Cand. Sci. (Biol.) (Institute of Animal Systematics and Ecology, Siberian Branch of the Russian Academy of Sciences, Novosibirsk) for assistance in conducting bird counts in 2014.

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