ИСТИНА

Calidris Sandpipers are deeply adapted to arctic environment, which indicates their evolution in tundra or tundra-like landscapes subjected to large spatial and likely structural changes during the Quaternary period of history. I have found that closely related Calidris species of western and eastern ‘origin’ within Eurasia differ in many their characteristics. Sandpipers that have evolved or survived in Beringia are almost without exceptions monogamous, site faithful on breeding grounds, and their acoustics at least at display flights are to a large extent similar. On the contrary, these patterns of behavior of the species typical for the western Eurasia (Europe and West Siberia) are much deviated from each other as well as from the species of Beringia. It seems that during the recent glaciations the Beringian species survived in a rather stable environment, and their evolution turned to be relatively slow resulting in preserving both the common conservative ancestral traits of the species and large species diversity. In the western Eurasia subjected to several extensive glaciations, the number of arctic species is strongly reduced, and the survivors had to undergo major changes in their behavior, including social organization that has become opportunistic. The social organization of each of several circumpolar species bears traits that appear to have evolved earlier.