[3] The genus name Phylloscopus is from Ancient Greek phullon, "leaf", and skopos, "seeker" (from skopeo, "to watch").

The single wing bar found in the southern and western populations distinguishes them from most similar species (except Arctic warbler P. borealis).

A latitude-based analysis of wintering birds indicated that more northerly P. trochiloides are smaller, i.e. this species does not seem to follow Bergmann's rule.

It breeds in lowland deciduous or mixed forest; non-breeding birds in the warmer parts of its range may move to montane habitat in summer.

P. t. plumbeitarsus is often split as distinct species, as it does not hybridize with viridianus in the narrow zone in the western Sayan Mountains where their ranges overlap.

Two-barred warbler, on the other hand, has a long song that can be clearly divided into a warbling part, followed by a series of up- and downslurred notes.