The red-flanked bluetail (Tarsiger cyanurus), also known as the orange-flanked bush-robin, is a small passerine bird that was formerly classed as a member of the thrush family Turdidae, but is now more generally considered to be an Old World flycatcher, Muscicapidae. It, and related species, are often called chats.
It is a migratory insectivorous species breeding in mixed coniferous forest with undergrowth in northern Asia and northeastern Europe, from Finland east across Siberia to Kamchatka and south to Japan. It winters mainly in southeastern Asia, in the Indian Subcontinent, the Himalayas, Taiwan, and northern Indochina. The breeding range is slowly expanding westwards through Finland (where up to 500 pairs now breeding), and it is a rare but increasing vagrant to western Europe, mainly to Great Britain. There have also been a few records in westernmost North America, mostly in western Alaska. source