Beskrivelse: Note the short and shallowly forked tail compared to nominate, giving a more compact impression. White on rump extends to upper tail coverts (black on nominate). In general darker, more ashy grey underwings than nominate. This central and eastern asian form breeds from Yenisey basin, Altai mountains, and northern Mongolia east to Manchuria, Sea of Okhotsk and Anadyrland (ref: Birds of the Western Palearctic 2.0.1).