Long-Term Dynamics of the Community Structure of Larks (Alaudidae, Aves) in the Northwestern Caspian Lowland

Resumo

Abstract—We studied the population structure and the number of larks in the steppe and semidesert zones of the Caspian Lowland (within the territories of the Alexandrov-Gai district of Saratov region, Russian Federation, and Dzhanybek and Bokey-Ordyn districts of the Western Kazakhstan region, Republic of Kazakhstan) in six key areas in 2011–2018. From the data obtained, dynamic series of the density dynamics were calculated for each lark species (T_gr, growth rate). The group statistical indicators were R, which is the fluctuation magnitude of the lark density, and u, the coefficient of variation, etc.; using Pearson’s χ² statistics, the normal type of lark distribution was checked in their habitats. A correlation analysis between the density of larks and values of the vegetation index (NDVI) was performed. It has been established that four species of lark (calandra lark, white-winged, black and lesser short-toed larks) show a tendency toward a decrease in their density in the Alexandrov-Gai district. The maximum decrease in abundance was observed for the white-winged lark (T_gr = –28.4%, R² = 0.785). In the Western Kazakhstan part of the habitat, the highest negative growth rate was recorded for the skylark (T_gr = –99.9%), while the maximum positive one was observed for the white-winged lark (T_gr = +25.2). It has been revealed that the lark density dynamics and the structure of their nesting population are influenced by the vegetation level in the previous year, as well as the vegetation structure associated with the soil and ground conditions of this mosaic landscape and the anthropogenic press, such as cattle pasture.