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. Voice: The yellow-crowned tyrannulet's song is a "2-noted, clear, plaintive 'wih-weér' (or 'free beer'), 2nd note higher, shorter, and stressed". It apparently differs little across the species' range.