Uncommon in thickets, bushy areas, and other dense low vegetation, particularly near water. Stays on the move in mid-level vegetation, often distinctively flicking its tail up high and fast like CAWA. Song a fast chattery trill, usually accelerating at end. ID: Small, round, and neckless. Long and narrow olive tail. In all plumages green above and yellow bellow. Differences subtle, so study contrast between darker ear coverts and crown with brighter yellow eyering and supercilium. Ad ?: solid black cap. Ad ?/1st-yr ?: reduced black cap variable in size. 1st-yr ?: little or no black in crown. In any birds with no black caps, always focus on shape, yellow supercilium, and tail flick.