arctic warbler complex | Kamchatka Leaf Warbler\Arctic Warbler/Japanese Leaf Warbler

This matter is well above my paygrade but it makes for interesting reading.
It is probably not the latest on the subject but sofar it appears to have been widely accepted.

On the species separation of 3 Arctic Warbler type Phylloscopus Leaf Warblers.
Arctic Warbler | Phylloscopus borealis | コムシクイ
Kamchatka Leaf Warbler | Phylloscopus examinandus | オオムシクイ
Japanese Leaf Warbler | Phylloscopus xanthodryas | メボソムシクイ

It argues that Arctic Warbler, Kamchatka Leaf Warbler and Japanese Leaf Warbler are three branches of the same tree and very hard to distinguish in the field - under normal circumstances even impossible.
Call and song of these birds are good for a proper ID to species level. In the breeding areas in the breeding season a field record may be identifiable. During migration it is considered impossible.

https://www.researchgate.net/publication/227729552_The_Arctic_Warbler_Phylloscopus_borealis-_three_anciently_separated_cryptic_species_revealed
(pdf is downloadable from within this page itself)

Publicado el septiembre 14, 2021 09:29 MAÑANA por housecrows