Description wikipedia

The white-tailed tyrannulet (Mecocerculus poecilocercus) is a species of bird in subfamily Elaeniinae of family Tyrannidae, the tyrant flycatchers. It is found in Colombia, Ecuador, and Peru. The white-tailed tyrannulet is about 11 cm (4.3 in) long and weighs 10 to 11 g (0.35 to 0.39 oz). The sexes have the same plumage. Adults have a medium gray crown. They have a thin white supercilium and a faint blackish stripe through the eye on an otherwise whitish face. Their upperparts are mostly greenish olive with a bright greenish yellow rump and uppertail coverts. Their wings are dusky with pale yellow edges on the flight feathers. Their wing coverts have white to pale buff tips that show as two bars on the closed wing. Their tail is dusky olive with a mostly to fully white outermost pair of feathers. Their throat is grayish white, their breast and sides grayish white with a darker grayish wash, and their belly and undertail coverts yellowish white. Both sexes of have a brown iris, a thin and pointed black bill, and medium gray legs and feet.