Yellow-crowned Tyrannulet

The yellow-crowned tyrannulet is 10 to 11 cm (3.9 to 4.3 in) long and weighs 6.5 to 8 g (0.23 to 0.28 oz). Adult males have a slate-gray to dark brown or blackish crown with a bright yellow to orange-yellow stripe along its middle. Their nape and back are bright olive-green. They have a grayish supercilium, a thin dark line through the eye, and a pale gray lower face. Their wings are dusky with two white to yellowish white bars. Their tail is dusky olive. Their throat is pale gray and their underparts pale to medium yellow with an olive wash on the breast. Females are smaller than males and have a paler gray crown and mid-crown stripe and slightly paler upperparts. Both sexes have a brown iris, a short and rounded black bill, and gray legs and feet.

The yellow-crowned tyrannulet has a disjunct distribution with two principal populations. One is found from north-central Puntarenas Province and northern San José Province on the Pacific slope of Costa Rica through Panama, south through western Colombia into western Ecuador as far as central Guayas Province, and east through northern Colombia into northwestern Venezuela. The other population is east of the Andes from eastern Colombia south through Ecuador and Peru into northern Bolivia and east through eastern Venezuela, the Guianas, and most of Amazonian Brazil. The yellow-crowned tyrannulet is a bird of the lowlands and foothills. It inhabits humid evergreen forest, especially its edges and shrubby openings in its interior, though also in the interior canopy. It also inhabits secondary forest, light woodland, coffee and citrus plantations, gardens, and suburban parks. In elevation it occurs up to 1,200 m (3,900 ft) in Costa Rica, 1,000 m (3,300 ft) in Colombia, 600 m (2,000 ft) in Ecuador, 1,050 m (3,400 ft) in Peru, and 1,200 m (3,900 ft) in Venezuela and Brazil.

The yellow-crowned tyrannulet feeds on insects and small fruits, especially mistletoe (Loranthaceae) berries. It forages singly or in pairs and only rarely joins mixed-species feeding flocks. It forages mostly in the forest's canopy, taking prey by gleaning while perched and while briefly hovering.