Red-billed Tyrannulet

The red-billed tyrannulet is 11.5 to 12 cm (4.5 to 4.7 in) long; four males weighed 11.3 to 13.8 g (0.40 to 0.49 oz) and two females 10.7 and 11.2 g (0.38 and 0.40 oz). The sexes have the same plumage. Adults have a pale gray or dusky olive crown. Their face, back, and rump are olive green. Their wing's lesser coverts are dusky with olive green tips and the median and greater coverts are dusky with pale greenish white edges. Their flight feathers are blackish with pale greenish white or white edges. Their tail is dusky with thin pale olive edges on the feathers. Voice: The red-billed tyrannulet's song has been described as "an accelerating and slightly descending series of clear notes, teeuw tew-tew-te-te-te-te-te-te-te or...a fast series of clear notes, the last two emphasized, tirtetetetete-whét-whét". Other authors describe it as "a rising chi-wheet, interspersed with a rich, chuckling pi'CHEE'CHEE'CHEE'CHEE".