A small, common but skulking bird of upper-montane forest understory. Dark brown upperparts, pale brown underparts and usually a white throat. Races differ, some males having a dark chest band and others uniformly buffy or pale below. Males usually have paler eyes than females. Similar to Large Scrubwren, but Mountain Mouse-Warbler lacks the rusty face. Variable, almost thrushlike song of loud, whistled notes. Also give scolding “chak!” and rasping calls.