Spatial distribution of Corvidae in transformed landscapes of Zhytomyr region

The spatial distribution and abundance of Corvidae species was studied in Zhytomyr region with a focus on rural and urban differences in the studied parameters. We selected Rook ( Corvus frugilegus L.), Western Jackdaw ( C. monedula L.), Hooded Crow ( C. cornix L.), Eurasian Magpie ( Pica pica L.), Eurasian Jay ( Garrulus glandarius L.), and Common Raven ( Corvus corax L.). All observations were made during 2009–2012. During the study period some 38 survey paths of more than 8,000 km were surveyed in 21 settlements of Zhytomyr region, among them 13 were in Zhytomyr city. The aim of our study was to establish the number and density of Corvidae in different seasons in the settlements of Zhytomyr region along a rural-urban gradient. The average density of Rooks was 55.9 ind. /km 2 . We also found a strong correlation between Rook density and the rural-urban gradient and observed that the number of Rooks wintering in cities significantly increased due to the influx from villages. The peak number of Rooks in villages was registered in the breeding and post-breeding season while in the cities it was high in winter and during the spring migration. The average density of Eurasian Magpie in the study area was 8.7 ind. /km 2 and had a weak correlation with the urban-rural gradient. The density of Eurasian Magpies in urban areas differs significantly only from the density of birds in villages with a population of ca. 1,000 people. The density of Magpies varied insignificantly within a narrow range during the three years of research, remaining relatively stable, which suggests that the species successfully adjusts to conditions in transformed landscapes. The urban-rural gradient significantly affects the density of Hooded Crows. The average density of birds in towns was 6.6 ind. /km 2 . In breeding period the urban birds had a low density and rural crows, on the contrary, had a high density, the density of birds in the nesting period was greater than in autumn and winter, due to the distribution of birds in their breeding territories and the start of the reproductive cycle. The average density of Eurasian Jackdaw was 9.7 ind. /km 2 and the rural-urban gradient significantly affected the number of birds. For jackdaws we registered high annual population dynamics. The peak number of birds was observed in the winter period in cities and small towns while in villages it was registered in the breeding and post-breeding season. The average density of Eurasian Jay was 2.4 ind. /km 2 and varied significantly in different settlements, although the fluctuation range was small (0.1–9.3 ind./km 2 ). The number of this species naturally decreases along the gradient of landscape transformation. The highest average density was typical in small villages (4.9 ind./km 2 ) and the lowest was found in medium-sized cities (1.5 ind./km 2 ). We have identified certain patterns in the seasonal dynamic of Eurasian Jays relative to the type of settlement. In urban areas the birds’ density was much higher in winter compared to the nesting period, and in villages we observed the reverse situation. The average density of Common Raven was 1.3 ind. /km 2 . The highest density was registered in small villages and was 2.2 ind. /km 2 , and the smallest in the villages of urban type (0.6 ind./km 2 ). The urban-rural gradient significantly affected the spatial distribution of Common Raven, but we cannot state that this bird increased or decreased its number along the gradient of urbanization, since the value of this indicator also depended on habitat conditions in specific settlements. The spatial distribution of Common Ravens varied seasonally and the highest density was typical in winter due to food migrations to human settlements.