Differentiation in breeding habitats of the birds of prey in the State Biosphere Nature Reserve Kerzhensky, Russia
The paper presents the data on the birds of prey breeding in the Kerzhensky State Nature Reserve, which is located in the N. Novgorod district; there are the results of the authors surveyed carried out in 2006-2010, data of Chronicles of the Reserve Nature, 2006, and the data from the database of the Reserve for the period of 2005-2006. Distribution of 48 nests has been analyzed in 42 breeding territories of 6 raptor species: Goshawk (Accipiter gentilis), Common Buzzard (Buteo buteo), Sparrowhawk (Accipiter nisus), Honey Buzzard (Pernis apivorus), Black Kite (Milvus migrans), Greater Spotted Eagle (Aquila clanga). A total of 60 cases of breeding were registered in the monitored nests since 2005 to 2010. Ecological niches of those species have been described: habitat and landscape preferences, relationships with conspecifics and other species. To identify differences between niches the Discriminant Analysis is performed, which included 7 parameters of landscapes and breeding habitats and nesting trees of raptors. Besides, the distances between living nests and rivers and between nearest neighbours were analyzed. Among 7 parameters under consideration, an area of open landscapes an area of open space within a radius of 1 km from the nest and the age of tree canopy are of prime importance for the differentiation of ecological niches. All species, except the Sparrowhawk, prefer to nest in the river valleys. Now under conditions of the Kerzhensky Reserve the most part of raptors are forced to nest in the river valleys, where unlike watersheds old and middle-aged forests have remained after the greatest fire in 1972, and the growth rate of trees is higher than on watersheds. In the analyzed community of raptors the intraspecific competition seems to be more significant than interspecific, that proved by the overlap of the breeding territories of some species, as well as the fact, that the inter-nest distances of conspecifics is more than the distances to nests of other species. Discriminant analysis has shown the similarity of ecological niches of Goshawks, Common Buzzards and Honey Buzzards, niches of Sparrowhawks overlaps with niches of these three species, niches of Black Kites, Greater Spotted Eagles are separated from each other and from niches of other species.