About Myiobius barbatus sulphureipygius (P.L.Sclater, 1857)
This subspecies, the whiskered myiobius, is very similar in appearance to several of its close relatives. It has olive upperparts, a distinct yellow rump, and a usually well-concealed yellow patch on the crown. Long rictal bristles surround its beak, forming a basket-like structure. Its underparts are greyish-olive, with a pale yellow belly. The tail is black and somewhat rounded. This bird is usually silent, but it occasionally produces a staccato "psik" call. It is widely distributed across tropical South America, specifically found in the Amazon basin across the northern half of Brazil, northeastern Peru, eastern Ecuador, eastern Colombia, southern Venezuela, Guyana, Suriname, and French Guiana. Its typical habitat is the lower canopy of humid rainforest, at altitudes below 900 m (3,000 ft). Compared to the black-tailed myiobius (M. atricaudus), it is more often found in the interior of forests, and in Amazonia it occurs at lower elevations than the tawny-breasted myiobius (M. villosus). Like other myiobius species, its diet consists mostly of insects, many of which it catches while flying. It frequently forages in small mixed flocks. When perched, this bird often droops its wings and fans its tail feathers in a posture similar to that of Old World fantails of the genus Rhipidura.
