Arctic Warbler

It is greyish-green above and off-white below, and its single wing bar distinguishes it from most similar species except the greenish warbler, though it is larger than that species with a heavier, dagger-like bill with a dark tip to the lower mandible (Wikipedia, general species account). It is strongly migratory, the entire population wintering in Southeast Asia, one of the longest migrations of any Old World insectivorous bird. (Wikipedia, general species account).

Arctic Warbler is a widespread leaf warbler of birch or mixed birch forest near water throughout its breeding range in Fennoscandia and the northern Palearctic, with a foothold in Alaska. The nest is on the ground in a low shrub and the song is a fast trill (Wikipedia, general species account). The species is a widespread leaf warbler in birch or mixed birch forest near water throughout its breeding range in Fennoscandia and the northern Palearctic. (Wikipedia, general species account).