Structural dynamics of the breeding population of larks (Alaudidae, Aves) in the semidesert of the Saratov Trans-Volga region

Resumo

According to our data on the density of breeding pairs of five lark species obtained from route censuses, the dynamics of their population in the Mezhuzenskii and Uzensko-Dyurinskii landscapes of the semidesert in the Caspian lowland is considered. Our five-year census work was carried out on key sites 25 km² in area, with mapping and description of the soils and vegetation using remote sensing techniques. Our comprehensive studies of these key areas have revealed the dynamics of the individual lark species characteristic of the northwestern part of the Trans-Volga region of the Caspian lowland and the changes in the level of vegetation of the plant component of individual landscape tracts depending on the moisture level in certain years. It is shown that, in the monotonous plain conditions, an important role in the distribution of the specific population of larks is played by the meso- and micro-relief, which determines the soil salinity, and the distribution of moisture and vegetation groups (which predetermine the features of bird habitats). The interannual variability of the population structure of larks is shown, which, in the modern conditions of consistently low anthropogenic pressure, is determined by the weather in specific years, which determines the level of vegetation and, therefore, changes in the nesting conditions of birds in specific habitats.