Pallas' Grasshopper Warbler

Pallas's grasshopper warbler, also known as the rusty-rumped warbler, is an Old World warbler of the genus Helopsaltes. The adult has a streaked brown back and whitish-grey underparts, unstreaked except on the undertail, and young birds are yellower below. It is very like the common grasshopper warbler but slightly larger, with white tips to the tail and tertials and a warmer brown rump (Wikipedia, general species account).

It breeds in the eastern Palearctic from the Altai, Mongolia and Transbaikalia to north-eastern China, the Korean Peninsula and the Sakhalin and Kuril Islands, and winters from India eastward to Indonesia. Four to seven eggs are laid in a ground nest in grass. The song is not the mechanical, insect-like reeling of the common grasshopper warbler but an inventive, Acrocephalus-like melody (Wikipedia, general species account).