Oustalet's Tyrannulet

Oustalet's tyrannulet is about 12 cm (4.7 in) long and weighs 9.4 to 10.5 g (0.33 to 0.37 oz). The sexes have the same plumage. Adults have yellowish lores whose color extends to a wide eye-ring. Their face is otherwise bright yellow with a blackish line through the eye that continues as a crescent around the ear coverts. Their crown and upperparts are olive. Their wings are dusky olive with yellowish olive edges on the flight feathers. Their wing coverts are dusky with yellowish tips that form two wing bars. Their tail is olive. Their underparts are yellow with a heavy wash of olive on the breast. Both sexes have a brown iris, a long, pointed, black bill, and gray legs and feet.

Oustalet's tyrannulet is found along a narrow band in southeastern Brazil from southern Bahia south to eastern Santa Catarina. It inhabits humid forest in the subtropical and tropical zones. It primarily is found in the forest interior and only occasionally at its borders. In elevation it ranges between 500 and 900 m (1,600 and 3,000 ft).

Oustalet's tyrannulet feeds primarily on insects and also other arthropods like spiders in its diet. It forages actively, mostly in the forest's sub-canopy and canopy. It typically perches horizontally on a branch, usually with its tail cocked up sometimes to the vertical, and makes short sallies to snatch or hover-glean prey from leaves and twigs. It typically forages in pairs or small family groups and almost always as part of a mixed-species feeding flock.