ИСТИНА

Following the biological species concept and taking in to account such criteria for assignment species rank as 1) morphological segregation, 2) molecular philogenetic data, 3) ecological, ethological and distribution characteristics, 4) reproductive relationships we analyzed 8 categories of taxons with ambiguous species rank. We treat Acrocephalus orientalis and Sitta arctica as cryptic species but with big genetic differentiation. In complex closely related taxons of Motacilla flava sensu lato and Lanius excubitor sensu lato we allocate western and eastern polytypic forms which treated as independent species. As closely related forms with morphological and genetic differentiation and sympatric zone we treat Casmerodius albus and Casmerodius modestus. As alopatric pair of species with morphological and genetic differentiation, we tread Rallus aquaticus and Rallus indicus and Oriolus oriolus and Oriolus kundoo, the differences in vocalization between both Oriolus species are described. The complex of Phylloscopus borealis sensu lato is one are not well investigated case yet. We treat Japanese taxon P. xantodrias as full species, but Kamchatka’s form examinandus as subspecies of Ph. borealis because the relationships of these forms are not clear yet and remind the same situation with Ph. collybita abietinus and Ph. c. tristis. The most palearctic forms of «herring gull complex» we treat as independent species including such as Larus michahellis, L. armenicus, L. fuscus, L. heuglini, L. vegae, L. mongolicus. Taxonomic status the gulls from the Taimyr peninsula requires further detailed investigation.