Tropical Gnatcatcher Polioptila plumbea

Tiny gray-and-white bird with long cocked tail and rather long slender bill. Fairly common in humid tropical forest canopy and edge. Extensive range across much of northern South America (east of the Andes, including the Marañón Valley) to eastern Brazil. Often in pairs, traveling with mixed-species flocks. Male has a black cap, gray on female.