Тенденции динамики населения птиц агроландшафтов степного Зауралья на рубеже столетий

Abstract

The dynamics of the bird community 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) is considered. In the conditions of intensive agriculture, the agrophytocenosis structure and features of the agricultural cultivation technology serve as the key factors for the differentiation of bird communities in the steppe agricultural landscape. A relatively high specific richness characterizes the bird community 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 prevalent in the area of agricultural landscape and, especially, in the cultivated crop fields. 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, livestock and sown land area reduction. 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 ( Alauda arvensis Linnaeus, 1758; Motacilla flava Linnaeus, 1758; Coturnix coturnix (Linnaeus, 1758); Tetrax tetrax (Linnaeus, 1758) et al). The opposite tendency for reduction in numbers is demonstrated by such species that avoid high closed grass stands ( Melanocorypha leucoptera (Pallas, 1811), Oenanthe oenanthe (Linnaeus, 1758), O. isabellina (Temminck, 1820) et al.). In general, the community density in the agricultural landscape increased by 2.3 times as compared to the pre-crisis period, the number of nesting species increased by 1.3 times. For the species that had formed strong ecological connectionswith agriculture (primarily, Corvidae family – Р iса р iс a (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.