I requested information from my friend Sergei Morozov, a Chukchi
Peninsula-based birder, on the status of Sandhill and Demoiselle
Cranes in NE Siberia. Here's a translation of what he wrote:
"Sandhill cranes have nested in Chukchi Peninsula since at least the
19th century. In recent decades, they colonized Northern Kamchatka,
Wrangell Island, and parts of Northern and Eastern Yakutia. It is
difficult to keep track of their expansion, because these areas are
very sparsely populated. As far as I know, all of them still migrate
to America. They came into contact with Yakutian populations of
Common and Siberian Cranes. That might explain recent sightings of
Sandhills in Southern Siberia (and China - V.D.) It is possible that
a new migration route to China will be eventually established.
Currently, Sandhills from Yakutia have to fly almost 2000 km to the
Northeast just to get to the Bering Strait.
Demoiselle Crane have never been registered within current Sandhill's
breeding range. However, "overshooting" birds have been recorded in
spring in Northern Russia, and in Central Yakutia.
In the Northeastern Yakutia, Common Cranes inhabit bogs and marshes.
Sandhills breed in more dry and open areas, such as upland
tundras and "tundrosteppes" (a relict type of Arctic grasslands
believed to be the dominant vegetation type in Siberia during the Ice
Age, now existing in small patches in Yakutia and some other
locations - V.D.) These tundrosteppes sometimes look very much like
Mongolian Steppes. It is entirely possible that an "overshooting"
Demoiselle Crane could sucsessfully oversummer in such a place, and
then join a flock of Sandhills. It would be less likely to join
Common Cranes, because they prefer different habitats."