Abstract
In the past, the Arctic Warbler Phylloscopus borealis (Blasius 1858) was considered a polytypic species by many authors. Recently, however, re-examination of the taxonomy of this species was conducted, and it was divided into three separate species; namely, the Arctic Warbler Phylloscopus borealis, Kamchatka Leaf Warbler P. examinandus, and Japanese Leaf Warbler P. xanthodryas. In contrast to the distinct genetic and vocalization differences, the morphological differences between these species are slight. Therefore, species identification is sometimes difficult in the field. In recent years, species identification for breeding males using discriminant analysis has been developed by the authors. However, species identification for females remains to be established. Here, we explain a method for the identification of the three allospecies of Phylloscopus [borealis] superspecies based on morphology. We hope that this study will serve as a useful identification guide to these species in the field, especially in bird banding.
