Small, sleek warbler; white belly contrasts with olive and green upperparts. Very difficult to separate from Eastern Bonelli’s of Eastern Europe. Best character is the call, a two-parted whistle "hu-eef" instead of the sharp “tzip” of Eastern Bonelli’s. Song, a short trilled phrase, is also quite similar to Eastern Bonelli’s. Compare with other leaf warblers; note present species’ plain face, olive-green wing panel (but no bright wing bars), and bright white underparts. Breeds in deciduous forests with oaks and beech, as well as in mixed forest with pines. Non-breeding habitat includes open scrub and open woodlands.