Arctic Warbler

The Arctic warbler (Phylloscopus borealis) is a widespread leaf warbler in birch or mixed birch forest near water throughout its breeding range in Fennoscandia and the northern Palearctic. It has established a foothold in North America, breeding in Alaska. This warbler is strongly migratory; the entire population winters in southeast Asia. It therefore has one of the longest migrations of any Old World insectivorous bird.

It traditionally included populations that breed in Kamchatka, the Kuril Islands and Japan, but genetic and vocal evidence strongly suggested these should be treated as separate species, and are all now considered distinct with the Kamchatka leaf warbler in Kamchatka, Hokkaido and the Kuril Islands, and the Japanese leaf warbler in Japan (except Hokkaido).