The spatial distribution of corvid nests in the urbanized environmental components (using the example of the Kirovsky district of Saratov)

Abstract

This study is dedicated to the nest placement peculiarities of four species of the Corvidae family: the Jackdaw, Rook, Hooded Crow, and Eurasian Magpie – in the urbanized environmental components on the territory of the Kirovsky district of Saratov. The following methods were used in the work: route and areal accounting, cartographic modelling, plotting isolines based on cartographic data, assessing the reliability of differences in the number of corvid nests using Pearson’s chi-squared test, determining the rate of urbanization of various areas of the model area based on the method used by E. L. Lykov, assessing the dependence of the number of nests on the rate of the territory urbanization using Spearman’s correlation coefficient. The distribution of 652 nests according to the biotopes was analyzed, the assessment of the corvid nesting density in various urban environmental habitats was carried out. The nest placement density reaches its maximum in the areas with abundant green places, a large number of nesting sites, both of natural and anthropogenic origin and low rate of human disturbance, being in the areas with low-rise buildings, in the forest belts, in the natural park “ Kumysnaya polyana”and in the old Voskresenskoe cemetery. The Jackdaw and the Rook are the most selective for breeding sites species, their nests being located in human buildings and on closely placed tall trees. The Hooded Crow nests most evenly and successfully occupied the habitats of Saratov. The Magpie’s nesting areas are more associated to large groups of woody vegetation, the highest density of its nest placement was observed in the natural and natural-anthropogenic components of the urban environment. The negative relation between the quantity of nests of the two species – the Hooded Crow and the Magpie – and the rate of the territory urbanization was revealed. The nesting of the Jackdaw and the Rook are affected mostly not by the urbanization rate, but the availability of breeding sites.