Yellow-crowned Tyrannulet

The yellow-crowned tyrannulet (Tyrannulus elatus) is a species of bird in subfamily Elaeniinae of family Tyrannidae, the tyrant flycatchers. It is found in Costa Rica, Panama, and in every mainland South American country except Argentina, Chile, Paraguay, and Uruguay. == Taxonomy and systematics == The yellow-crowned tyrannulet was originally described as Sylvia elata in 1790; it was reclassified in genus Tyrannulus in 1816. It is the only member of genus Tyrannulus and has no subspecies. == Description == 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.…