Description wikipedia

The white-crested tyrannulet (Serpophaga subcristata) is a small species of bird in the family Tyrannidae, the tyrant flycatchers. It is found in Argentina, Bolivia, Brazil, Paraguay, and Uruguay. The white-crested tyrannulet is 11 cm (4.3 in) long and weighs 6 to 8.6 g (0.21 to 0.30 oz). The sexes have the same plumage. Adults of the nominate subspecies have a gray crown and nape with white central crown feathers that are usually hidden but sometimes raised as a crest. They have a thin white supercilium, a white partial eye-ring, and a dusky line through the eye on an otherwise grayish white face. Their upperparts are grayish olive. Their wings are dusky to blackish with pale buffy edges to most of the flight feathers and two whitish to pale buffy wing bars. Their tail is dusky with whitish edges on the outer feathers. Their chin and throat are white, their breast gray, and their belly pale yellow. Juveniles have buff wing bars and little or no white on the crown. Subspecies S. s. straminea is very similar to the nominate but with a brighter yellow belly. S. s. munda is larger than the nominate. Its upperparts are gray with a faint olive tinge, its wing bars are white, and its belly is white with sometimes a faint creamy yellow tinge. Both sexes of all subspecies have a dark brown iris, a black bill, and gray legs and feet.