Tendencies in the Dynamics of Bird Communities in Agricultural Landscapes of the Steppe Trans-Urals at the Turn of the Century

Аннотация

Abstract—This paper considers the dynamics of bird communities in agricultural landscapes of the Trans-Urals steppe from the period of heavy agricultural intensification (1988–1992) until the decline of agricultural production (2000–2008). In the conditions of intensive agriculture, the agrophytocenosis structure and features of the agricultural cultivation technology serve as key factors for the differentiation of bird communities in the steppe agricultural landscape. A relatively high specific richness characterizes bird communities of virgin pastures, while among field agrocenoses, i.e., in the areas seeded with perennial grass, the population is much poorer in the grain fields, which are prevalent in the area of agricultural landscapes and, especially, in fields of cultivated crops. During the period of agricultural stability, both the living conditions and the bird community structure in the agricultural landscape remained relatively constant from year to year. The economic crisis that took place at the end of the 20th century caused a deep decline in agricultural production, namely, a decrease in livestock and a reduction in the area of land sown. The restorative successions of vegetation in pastures and fallow lands led to significant changes in the conditions of bird habitats. For many species these changes meant an increase in the ecological capacity of the environment and contributed to the growth of their populations in the agricultural landscape (Alauda arvensis Linnaeus, 1758; Motacilla flava Linnaeus, 1758; Coturnix coturnix (Linnaeus, 1758); Tetrax tetrax (Linnaeus, 1758), etc.). The opposite tendency for reduction in numbers is demonstrated by species that avoid high closed grass stands (Melanocorypha leucoptera (Pallas, 1811), Oenanthe oenanthe (Linnaeus, 1758), and O. isabellina (Temminck, 1820), etc.). In general, the community density in the agricultural landscape increased by 2.3 times as compared to the precrisis period, and the number of nesting species increased by 1.3 times. For the species that had formed strong ecological connections with agriculture (primarily, the Corvidae family Рiса рiсa (Linnaeus, 1758); Corvus monedula Linnaeus, 1758; C. frugilegus Linnaeus, 1758; C. cornix Linnaeus, 1758), the decline in the agricultural production and the reduction of functioning agrocenoses had opposite consequences and caused the decline in their numbers in the agricultural landscape.