Small songbird, a member of the Arctic Warbler complex, this species looks essentially identical to Arctic Warbler and Kamchatka Leaf Warbler but is more evenly yellowish. Normally only distinguished in the field by breeding range and song: breeds in forests on all of the main Japanese islands except Hokkaido, where it is replaced in summer by Kamchatka Leaf Warbler. Favors foothill to montane areas with dense brushy understory; can be found in more open wooded habitats in migration and on wintering grounds. Song resembles that of Arctic in general pitch and register but is less uniform, like a more rising and falling version of Arctic’s song. Call also similar but averages lower in pitch.