Western Olivaceous Flatbill

The western olivaceous flatbill is 13.5 to 15 cm (5.3 to 5.9 in) long and weighs 14 to 24.5 g (0.49 to 0.86 oz). The sexes have the same plumage. Adults of the nominate subspecies R. a. aequinoctialis have a dark olive head with a somewhat indistinct white eye-ring. Their entire upperparts are dark olive. Their wings are dusky with yellowish edges on the wing coverts and secondaries that form two dull wing bars. Their tertials have buffy to yellow edges. Their tail is a dusky with paler outer edges on the feathers. Voice: Researchers have identified three vocalizations of the western olivaceous flatbill. Its song is a "series of typically 5-10 whistles, initially flat and buzzy, gradually shifting to louder purer whistles which accelerate and rise in pitch" and which sometimes are followed by a series of stutters.