Marsh Grassbird

The marsh grassbird is smaller than a sparrow. The upperparts are brown with dark lengthwise streaks, there is a conspicuous white eyebrow, and the belly is beige. The tail is long and rounded. The song consists of crackling trills, and the alarm call is a sharp chak, chak. It sings either perched on reed tops or by rising in a steep arc, like the sedge warbler and its close relatives. (Russian Wikipedia, general species account)

It occurs in China, Japan (Honshu), Mongolia and Russia, and has been recorded in South Korea. In China it has two areas: the northeast coast of the Liaodong Gulf, where it is migratory, and the lower Yangtze, where it is resident. In Mongolia it has been noted in the far east, and in Russia at Lake Khanka and in the Uldza delta at Barun-Torey in the Daurski Reserve, where it disappeared with the drying of the river and the degradation of the reedbeds. It nests in marshes with large stands of reed. (Russian Wikipedia, general species account)