Sakhalin Leaf Warbler Phylloscopus borealoides

Small songbird, virtually identical in plumage to Pale-legged Leaf Warbler, of which it was formerly considered a subspecies. Vertical tail pumping distinguishes this species from most others in its range except Pale-legged. Forages through the different layers of forest and like Pale-legged (and unlike most other leaf warblers) sometimes forages on the ground. Call note is a hard metallic “pit,” similar to Pale-legged, but marginally lower in frequency (visible on spectrogram); song a series of rhythmic whistles with clear distinctions between each note, very unlike the high, rapid trill of Pale-legged. Breeds in forest edges and clearings; can be found in a range of wooded habitats in migration and on wintering grounds.