Characteristics of the great bustard (Otis tarda) (Otididae, Aves) habitats in the Trans-Volga region according to food availability during the chick rearing period

Abstract

The results of our studies of potential nesting sites for bustards in the Saratov Trans-Volga region are presented. Characteristics of plant communities, as well as the quantitative and qualitative composition of arthropods in these areas, are given. Specific materials obtained in 2017–2021 at 6 plots are given, namely: crops of winter wheat, millet, and sunflower; fallows of various ages; and young (2nd stage) and old virgin lands. The obtained results are compared with the data of previous years. The obtained results on the state of the forage base of bustards allow us to conclude that loss of nesting habitats by birds of this species has actually occurred. Those areas, where, despite the decrease in the abundance of insects, there are still enough of them to feed the chicks, are not used by bustards as nesting stations. These are fallows of various ages and virgin lands. The lack of a sufficient number of arthropods necessary for feeding chicks in those places where bustards prefer to nest, namely, cereals crops, leads to catastrophic consequences for reproduction, and, consequently, the survival of the species. The numbers of large orthoptera and beetles in winter crops, reflecting biomass indicators, have decreased by 10 times compared to 2000, during the period of extensive agriculture. The intensification of agricultural production, the use of pesticides on various crops, as well as the change in the structure of crop rotation are the main causes for the insufficient food supply during the period of rearing chicks. The results obtained give grounds to believe that the number of bustards will continue to decline due to the inability to raise their offspring as a result of the lack of food supply.