The lanceolated warbler 
(Chích đầm lầy nhỏ, Locustella lanceolata)

The lanceolated warbler (Locustella lanceolata) is a species of Old World warbler in the grass warbler genus Locustella.
The bird breeds from northeast European Russia across the Palearctic to northern Hokkaidō, Japan. 
It is migratory, wintering in Southeast Asia.

The genus name Locustella is from Latin and is a diminutive of locusta, "grasshopper".
The specific lanceolata is Latin for "spear-shaped" and refers to the streaks on the breast.