|Taxonomic Notes :||It has been proposed that this species be split into three. Since these three taxa are practically inseparable in the field except by their vocalisations, they are all retained here under Arctic Warbler, and there has been no attempt to differentiate the images on OBI except where the photo was taken in the hand or in the breeding season well within the known breeding area.
The three suggested new species (with breeding ranges in parentheses) are:
1. Arctic Warbler Phylloscopus borealis (sensu stricto) (continental Eurasia and Alaska)
2. Kamchatka Leaf Warbler Phylloscopus examinandus (Kamchatka [at least the southern part], Sakhalin, Hokkaido and Kurile Islands)
3. Japanese Leaf Warbler Phylloscopus xanthodryas (Japan except Hokkaido).
Alström, P., Saitoh, T., Williams, D., Nishiumi, I., Shigeta, Y., Ueda, K., Irestedt, M., Björklund, M., and Olson, U. (2011). The Arctic Warbler Phylloscopus borealis – three anciently separated cryptic species revealed. Ibis 153(2): 395–410