The article presents the results of the vitality structure analysis of 23 natural cenopopulations of Colchicum bulbocodium subsp. versicolor in the Lower Volga region in the years 2014–2019. The viability of cenopopulations within the studied region varied greatly over the years of monitoring, from 0.45 to 1.51. Cenopopulations in the northeast of the Lower Volga region, compared to southwestern cenopopulations, exhibited lower vitality index, greater instability and a wider range of variability of the latter parameter. Also, most morphological characters poorly correlated with one another. A high correlation was revealed only between two characters, and a medium correlation only in six pairs of characters. The largest number of significant-correlation relationships was registered for the plant height and diameter, the length and width of the lower leaf, and the length of the marigold. Based on the I_Q parameter and the Q criterion, the absolute majority of cenopopulations were prosperous in all the years of monitoring. The depressive state was found only in some cenopopulations and only in certain years of monitoring (mainly in 2018). Considering that, compared to other years of monitoring, in the spring of 2018, the average temperatures during the period of the subspecies’ active vegetation and flowering were extremely low, we suggested that it could have resulted in extreme growing conditions for the subspecies in the studied region and, consequently, a decrease in vitality of cenopopulations.

The paper attempts to link changes in quantitative characteristics of the community of free-living planktonic ciliates and the nature of their vertical distribution with the operation mode of the hydroelectric power station in the reservoir. Low values of the abundance (8–1,560 thousand cells / m³) and biomass (0.1–66.9 mg / m³) of ciliates in the water column, and a fairly wide range of their variation in the reservoir are probably due to the oscillatory nature of the hydrological regime in the regulated river conditions. The vertical distribution of free-living planktonic ciliates of the near-dam section of the Kuibyshev reservoir was studied at all times of the day on all days of the week. The species were distributed throughout the water column to the bottom with some preference for the surface (0–2 m) and medium (4–10 m) layers. There was no clear attachment of individual species to certain layers in the conditions of homothermy. The preference for certain horizons is due to some biological characteristics of the species (for example, peritriches on the coenobia of algae in the surface layers), departure from “blooming spots”, etc. No data in favor of vertical migrations or “turbulent transport” has yet been revealed. The influence of the weekly regime of regulation of the Zhigulevskaya HPS, in which at the end of the working week, the fluctuation amplitude of many hydrological parameters probably decreases, is manifested in an increase in the abundance and biomass of planktonic ciliates at this time.The nature of the daily change in the average ciliates abundance in the water column was the same for a variant of the community in working days and was in antiphase with the change in the community abundance on weekends, namely: the maximum number on working days and on weekends was recorded in the evening (20.00) and in the daytime (14.00), respectively.

Based on the results of our analysis, a classification of bird species of the Kyrgyz mountain ridge (Northern Tien Shan) was compiled according to their preference for habitats and occurrence throughout the year. The program of factorial classification used for this unites species according to the maximum similarity in their distribution and stay in an unspecified number of clusters. In total, 4 supertypes and 12 types of preferences have been identified along the Kyrgyz ridge. In the supertype of birds that prefer undeveloped areas, 6 types were distinguished, namely, the species choosing: 1 – high mountains, 2 – high and medium mountains, 3 – medium mountains, 4 – medium mountains and foothills, 5 – foothills, and 6 – found at all heights. The supertype of birds preferring built-up areas is represented by one type only: the species preferring foothill sheaths and villages, and the supertype of birds preferring rivers and their banks is represented by four types, namely, the species preferring: high-mountain rivers in the summer and autumn; high-altitude and mid-mountain rivers in the spring and summer; mid-mountain rivers in the autumn; and foothill rivers in the first half of the summer. The supertype uniting species found in all habitats is represented by one type of preference, namely, found throughout the whole year. It is shown that of the 154 recorded bird species, most were found in undeveloped habitats, and 6 and 12 times less were in built-up areas and rivers, including their banks. In undeveloped areas, most bird species prefer high- and mid-mountainous landscapes and half as many prefer foothill landscapes. In residential landscapes, most species tend to the foothills, and among rivers, they prefer high-altitude and mid-mountain areas. At to the seasons, the maximum number of species was recorded in the spring-summer and summer periods.

The structure and spatial distribution of picoseston in the Saratov reservoir in July 2011 and August 2014 are described. On average, the total abundance of cells and particles forming picoseston was 1.87±0.73×10⁶ cells (part.)/mL; and the total biomass of picoseston was 43.8±19.4 µg C/L. During the study period, solitary heterotrophic bacteria and phototrophic picocyanobacteria prevailed in the picoseston of the Saratov reservoir, amounting to 77–100% of its total abundance and biomass. The proportion of picodetrital particles was extremely small (on average, 4.1% of the total biomass of picoseston). The high heterogeneity of picoceston distribution (Cv is 130% and 110% for abundance and biomass, respectively) was found in the Saratov reservoir during the study period. On average, the abundance and biomass of heterotrophic bacterioplaknton and picodetritus at stations of the tributary estuaries were slightly higher than in the riverbed. At the same time, the abundance of picocyanobacteria was higher, and the biomass was lower at the estuarine stations compared to the riverbed ones. The total number of bacterioplankton and autotrophic picoplankton in the Saratov reservoir in 2011 and 2014 corresponded to the mesotrophic level of productivity. Picodetrital particles, in contrast to the Upper Volga and Kama reservoirs, make no significant contribution to the planktonic food webs of the Saratov reservoir, at least during the study period.

Birdsong is one of the most complex signals in the animal world, as it may consist of many different sounds grouped according to certain rules. Singing acts as a distant signal, indicating, e.g., the species and gender identity of the singer. However, territorial songbirds also use singing as an interactive social signal during territorial disputes, as well while interacting with female. In these contexts, males vary the type and timing of their songs to convey graded information about their motivational state, and those variations can play a role in communication. In this review, we considered how male songbirds vary their singing in territorial context. To study such variations, researchers usually simulated territorial intrusion by broadcasting conspecific singing in territories, including singing modified in a manner necessary for the researcher. For comparison, we considered briefly how singing vary in intersexual context. The author of the paper focuses on the role of singing complexity in communication. Therefore, not all known context-dependent changes in singing are considered, but only those related to “complexity”: the diversity of song/sound types and the transitional patterns of different song/sound types in the course of singing. Our review has shown that males change their singing when they detect environmental changes such as the appearance of a female or a competitor as follows: 1) song rate increases, 2) syllable rate increases, 3) song-type switching rate increases, 4) song-type diversity increases (i.e., the observed repertoire size), and 5) longer and more complex songs are predominantly used. In some species, the song bout organization may also change, but the data is still scarce. Typically, one or more, but not all the aforementioned acoustic behaviors have been found in a given song-bird species. All these behaviors (tactics) come down to a single strategy, namely: maximizing the acoustic diversity over a short period of time (e.g., several minutes), that is, increasing the number of different song and/or note types. The proximate causes of how the increased acoustic diversity work in the territorial competition context might lie in a sensory, or perceptual bias of the receiver. Namely, habituation should occur to repeated presentation of the same song type faster than to presentation of different song types. Therefore, by vocalizing more diversely, males more effectively influence the signal recipient’s behavior.

The dynamics of the numbers of larks inhabiting several areas differing in physical and geographical (landscape) conditions and the level of anthropogenic impact (pasture) on the natural environment is considered. Four key sites (“Akhmat”, “Zhdanov”, “Baiguzha”, and “Vetelki”) are located on the Priuzenskaya plain in the Aleksandrovo-Gaysky district of the Saratov region. The described territory is characterized by a high mosaicity of the facial structure of landscapes and, consequently, plant communities. This habitat diversity forms the structure of the communities as well as the population density of the individual lark species at the key sites surveyed. Our study of the dynamics of the numbers of species inhabiting the named key areas was carried out using calculations of logarithmic trends in the bird densities by the years of our study. In total, there were five species of larks (Alauda arvensis, Calandrella rufescens, Melanocorypha calandra, M. leucoptera, and M. yeltoniensis). As a result of our statistical processing of the obtained materials, significant differences were found in the dynamics of the numbers of individual lark species nesting in the key areas differing in landscape-ecological conditions and the level of anthropogenic load on ecosystems. In all likelihood, the dynamics of the density of the nesting lark population in the semi-desert of the Trans-Volga region is associated with both changes in the structure of habitats and, apparently, with the dynamics of the abundance of these species in the main part of their habitats, and with a number of other factors.