Description wikipedia

The mottle-cheeked tyrannulet (Phylloscartes ventralis) is a generally common, small species of bird in the family Tyrannidae, the tyrant flycatchers. It is found in Argentina, Bolivia, Brazil, Paraguay, Peru, and Uruguay. The mottle-cheeked tyrannulet is about 12 cm (4.7 in) long and weighs about 9 g (0.32 oz). The sexes have the same plumage, and the subspecies also have essentially the same plumage as well. Adults have a short thin whitish supercilium, an indistinct broken whitish eye-ring, a dusky line through the eye, a wide whitish and dusky crescent below the eye, a dusky "moustache", and the eponymous whitish and dusky mottled cheeks. Their crown, nape, back, and rump are dark olive. Their wings are dusky with bright olive-yellow outer webs at the base of the flight feathers. Their wing coverts have pale yellow to yellow tips that form two wing bars. Their tail is dusky with bright olive-yellow outer webs at the base of the feathers. Their chin and upper throat are whitish. The rest of their underparts vary from olive grayish to mostly yellowish with faint olive markings. Their belly and undertail coverts can be a paler yellow. Both sexes of all subspecies have a dark brown iris, a long, flat, pointed black bill with a pinkish to yellowish base to the mandible, and slate to bluish gray legs and feet.