Abstract
The Arctic Warbler Phylloscopus borealis (Blasius) breeds across the northern Palaearctic and northwesternmost Nearctic, from northern Scandinavia to Alaska, extending south to southern Japan. Seven subspecies have been described based on subtle morphological characteristics, although the taxonomy varies considerably among different authors. To elucidate this issue, we studied molecular phylogeny, morphometrics and bioacoustics among breeding populations throughout the range of the Arctic Warbler. In addition, to determine the correct application of available scientific names, mitochondrial DNA was sequenced from three name-bearing type specimens collected on migration or in their winter quarters. Based on the congruent variation in mitochondrial DNA, morphology and vocalizations, we propose that three distinct species be recognized: Arctic Warbler Phylloscopus borealis (continental Eurasia and Alaska), Kamchatka Leaf Warbler Phylloscopus examinandus (Kamchatka, Sakhalin, Hokkaido and Kurile Islands), and Japanese Leaf Warbler Phylloscopus xanthodryas (Japan except Hokkaido). We also propose Japanese names for each species: Arctic Warbler Ko-mushikui, Kamchatka Leaf Warbler O-mushikui and Japanese Leaf Warbler Meboso-mushikui.
