Olivaceous thornbill

The olivaceous thornbill (Chalcostigma olivaceum) is a species of hummingbird in the "coquettes", tribe Lesbiini of subfamily Lesbiinae. It is found in Bolivia and Peru.

The olivaceous thornbill is 12 to 15 cm (4.7 to 5.9 in) long. One male specimen weighed 8.2 g (0.29 oz) and a female one 6.6 g (0.23 oz). Both sexes have a short black bill. Adult males of the nominate subspecies are mostly dull dark bronzy or olive green, including the tail. The face and throat are dark sooty gray. It has a narrow gorget that is glittering green at the throat and shades through yellow, pink, and purple to blue at its bottom. The adult nominate female is essentially the same but the gorget is much smaller or may be absent. Juveniles have tan margins on some feathers; males' throats are gray brown and females' gray brown with pale margins. C. o. pallens is similar to the nominate but smaller and overall paler. The upperparts have a grayish cast to the bronzy or olive green, the tail is bronzy olive brown, and the underparts are dark sooty brown.