A brilliantly colored, tiny, and active species of dense woodlands where it feeds at upper levels, primarily on mistletoe berries and sometimes joins mixed flocks. Easy to miss despite bright colors and flitting movements. Its blue crown, bright underparts (geographically varying from yellow green to orange), small size, and tiny bill eliminate other species. Its calls include a lively “beep” given singly or in series, a rapid “whip-ip,” a rough “djip,” and a plaintive “wheee.” Song is a rapid jumble of tinkling, squeaky, and whistled notes.