Radde's warbler 
(Phylloscopus schwarzi)

Radde's warbler (Phylloscopus schwarzi) is a leaf warbler which breeds in Siberia.
This warbler is strongly migratory and winters in Southeast Asia. 
Radde's warbler breeds in southern parts of Central and Eastern Siberia as far east as Korea and Manchuria.

Leaf warblers were formerly included in the Old World warbler family but are now considered to belong to the family Phylloscopidae, introduced in 2006.
The name Phylloscopus combines the Ancient Greek phullon meaning "leaf" and skopos meaning "seeker" (from skopeo, "to watch").