What are two main distinctions between the east Siberian greenish warbler and the west Siberian greenish warbler?

The East Siberian Greenish Warbler (Phylloscopus trochiloides plumbeitarsus) is typically characterized by its more olive-green coloration, while the West Siberian Greenish Warbler (Phylloscopus trochiloides viridanus) tends to have a brighter yellowish hue. Additionally, their song differs; the East Siberian variety has a more varied and complex song, whereas the West Siberian has a simpler, more monotonous vocalization. These distinctions in plumage and vocalization help ornithologists differentiate between the two subspecies.