Choco Vireo

The Choco vireo is about 12.5 cm (4.9 in) long and weighs about 11 to 11.5 g (0.39 to 0.41 oz). The sexes have the same plumage. Adults have an olive crown, a yellow buff to dingy yellowish supercilium, white arcs above and below the eye, a dusky stripe from the lores through the eye, and yellow-buff ear coverts. Their nape and upperparts are olive that becomes brighter by the rump. Their wing coverts are dusky gray with wide white tips that show as two wing bars. Their primaries and secondaries are dark brown with thin yellow-green or white edges. Their central pair of rectrices are olive and the rest dark brown; the outer three pairs have pale dingy white to pale brown edges. Their throat is yellow-tinged whitish, their breast buff yellow, their belly dingy white with olive sides, and their undertail coverts straw yellow. They have a dark brown iris, a blackish maxilla, a pale dusky mandible with a paler base, and bluish gray legs and feet. Juveniles have a paler supercilium, more yellow-tinged wing bars, and paler, more creamy, underparts than adults.

The Choco vireo is a bird of the Chocó region, which is famed for its high biological diversity. As of 2023 it was known from only four locations between Colombia's Alto de Pisiones in the north and near La Delicia, Pichincha Province, Ecuador in the south. Searches between those areas have not found the species. The Choco vireo primarily inhabits the interior and edges of primary rainforest on both level ground and on steep slopes. Its habitat is characterized by a canopy about 20 to 30 m (65 to 100 ft) high with gaps made by fallen trees; the trees are heavy with moss and epiphytes. One source states that its elevational span is 1,200 to 2,100 m (3,900 to 6,900 ft) and another says 800 to 1,600 m (2,600 to 5,200 ft).

The Choco vireo's diet is not known in detail but includes both adult and larval insects. It takes most prey by gleaning from the undersides of leaves while perched and sometimes hanging upside-down. It typically feeds singly or in pairs, and usually in the forest's subcanopy and canopy though sometimes lower at edges and in treefall gaps. It often joins mixed-species feeding flocks as they pass through its territory but seldom continues beyond the territory's boundary.