Chico's Tyrannulet

Chico's tyrannulet is about 10 cm (3.9 in) long; one male weighed 5.5 g (0.19 oz). The sexes have the same plumage; males are larger than females. Adults have an olive-green crown, back, and rump. Their face is slightly paler and more green. Their wings are dull blackish with a faint olive cast. The wing coverts have yellow edges and the secondaries and outer primaries have thinner yellow edges. Their tail is dull blackish with a faint olive cast. Their throat is pale green, their breast green washed with yellow, and their belly and undertail coverts bright yellow. Voice: Chico's tyrannulet has at least four vocalizations, all made by both sexes, though recordings are sparse. The most commonly heard is a call, "a distinctly double-noted 'tweep-tweep' (occasionally single- or triple-noted), with variants and different inflections". What is thought to be its dawn song is a single "tweep" note repeated at intervals of three to five seconds.