Features of the population dynamics of larks (Alaudidae, Aves) in the semi-desert zone of the Saratov Trans-Volga region

The paper presents the results of our long-term monitoring of the family of larks (Alauda arvensis L., Melanocorypha calandra L., M. leucoptera Pallas, M. yeltoniensis J. R. Forster and Calandrella rufescens Vieillot) in the semi-desert zone of the Saratov Trans-Volga region. Bird censuses were carried out at 4 key sites on permanent routes during the nesting period, the total length of the census transects was 792 km. Statistical indicators of population dynamics were calculated, namely: the growth rates (Tnp.) and average density values (ind. / 100 ha) of each lark species. A statistical multivariate factor analysis (F-test) was carried out, with the help of which we were able to reveal the influence of a whole range of factors on the lark density dynamics. Changes in habitat conditions at the key areas (Fcrit. = 1.30, p = 0.003), as well as weather factors (Fcrit. = 1.39, p = 0.004) of particular years, have a significant impact on the density dynamics of larks. Evaluation of the variance showed heterogeneity of the sample (St = 0.119, p = 0.006), therefore, the average densities of larks differs significantly from each other. Thus, the structure of the lark community and the annual density of each species are the result of the environmental conditions of the habitats at each key site, and the weather conditions of particular years.