Density of Larks (Alaudidae, Aves) of the Semi-desert of the Trans-Volga Region in Connection with the Landscape Wetting Dynamics

Abstract

The dynamics of the density of nesting pairs of five lark species (Alaudidae) living on the territories of the Mezhuzenskii and Uzeno-Dyurinskii Plains, on the northwestern tip of the Caspian Lowland, and in the semi-desert of the Aleksandrovo-Gayskii district of Saratov oblast, and its relationship with Selyaninov’s hydrothermal coefficient (HTC) are considered. This research was carried out annually on 40 fixed routes of 1 km each in the breeding period of the annual lark cycle from 2011 to 2019. It was established that the abundance dynamics trends were negative in four lark species, namely, the Calandra Lark (Melanocorypha calandra), the White-winged Lark (M. leucoptera), the Black Lark (M. yeltoniensis), and the Lesser Short-toed Lark (Calandrella rufescens); and were positive in the Skylark (Alauda arvensis). The calculated trend of HTC indicators for these territories demonstrates a 5.4% annual increase in the moistening of the semi-desert zone of our survey area. To assess the relationship of the density of different lark species to the values of the HTC, we calculated the Spearman correlation coefficients. When analyzing the data obtained, it was found that a high positive correlation of density with the HTC was observed for the Skylark, Calandra Lark, and Black Lark; no such relationship was found in the White-winged Lark, and a high negative correlation of the density of nesting pairs with the HTC was found in the Lesser Short-toed Lark. Based on our research, it can be assumed that moistening of the semi-desert territory is one of the main factors determining the abundance dynamics of larks. The heat–moisture ratio determines the level of vegetation and, accordingly, the quality of habitats for these land-nesting birds.