ИСТИНА

Cis-Caucasia steppes of Southern Russia were actively afforested throughout the 20th century. The result of such a deep anthropogenic change of steppes has become the emergences of a unique zone within the conditions contribute to resettlement of different taxa of birds towards each other from the European deciduous forest and the Caucasus forests to the north and south respectively. Our study focuses on the abundance, distribution and interaction between two closely related species of nightingales, the Common Nightingale (Luscinia megarhynchos) and the Thrush Nightingale (L. luscinia) in Cis-Caucasia steppes of Southern Russia. These species have subsequently come into secondary contact in Central and Eastern Europe and Cis-Caucasia steppes. Interspecific hybridization has proven for mixed population of nightingales in Europe. Analysed data were gathered during May and June 2017 in Cis-Caucasia steppes. Within each population ecologically important traits were measured in each male and a blood sample was collected for genetic analysis. The zone of secondary contact of nightingales in Cis-Caucasia steppes was located in the north-eastern part of the Krasnodar region and in the western part of Republic of Kalmykia according to study of this region conducted 30 years ago. At present, mixed populations have found only in the Kalmykia. Several individuals have identified by morphological characters as interspecies hybrids, so we assume hybridization in this population. In the investigated areas of Krasnodar region, the Common Nightingale has not found, although it was erstwhile common in these areas. The number of the Thrush nightingale, on the contrary, has increased and the obtained date shows the further spreading the species to the south. These results characterize Cis-Caucasia zone of repeated contact of the Thrush and the Common nightingales as a sufficiently dynamic area, the reason of which is probably the fact that the origin is relatively young and anthropogenic.