Specificity of Studying Spatial and Typological Variations in Bird Assemblages across Certain Species Groups and Their Distribution (Using the Example of Corvidae)

The average numbers of birds recorded over the first half of summer (May 16–July 15) from 1880 to 2019 (with intervals predominantly since 1960) have been analyzed to identify the spatial typological structures and organization of bird assemblages in northern Eurasia. Overall, 352 researchers have been involved in collecting this material for 110 years. Data processing is carried out with multivariate statistics methods, including cluster analyses, qualitative linear approximation to the connectivity matrices, and the gradient and expert approaches. Therefore, the main spatial trends in corvid communities and the natural and anthropogenic regimes correlating with them have been identified. The relationship between the spatial variability of the assemblages of these birds and the heterogeneity of habitats has been assessed. The quasi-fractal patterns of spatial differentiation of communities are shown. The analysis of corvid groups based on factor classification give unsatisfactory results on approximation for spatial and typological variability in their assemblage abundance at the confined-landscape scale level, while it shows rather high informativity of classification of species abundance across all 8144 habitats. A satisfactory explanation of heterogeneity in communities of Corvidae was achieved only after averaging the values for abundances of bird species associated with landcover types. It is impossible to get an idea about them based on cluster analysis, while the gradient and expert (speculative) approaches followed by estimating the informativity of concepts may be considered acceptable for such generalizations. The techniques indicated above contribute to a higher informativity score incorporating representiveness by the average abundance values, which had sevenfold and threefold increases in terms of the explained dispersion and the multiple coefficients of correlation, respectively. In addition, structural classifications of species and, especially, territorial communities acquire a two-dimensional reticular (grid-based) structure. The formalized classification of corvid species is seven times and two times more informative about distribution similarity and assemblages, respectively, than the expert and speculative ideas.