The Blue-black Grassquit, Volatinia jacarina, is a small bird of the family Thraupidae. Sometimes classified in the bunting and American sparrow family Emberizidae, more recent studies have shown it to belong in the Thraupidae. It breeds from southern Mexico through Central America, and South America as far as northern Chile, Argentina and Paraguay, and on Trinidad and Tobago. It is the only member of the genus Volatinia.
This is a common bird in semi-open areas, including cultivation and gardens. It makes a small cup nest, with a typical clutch of one to three pale green eggs blotched with reddish brown. Both sexes incubate for 9"?10 days, with about the same period again for the young to fledge.
Adult Blue-black Grassquits are 10.2cm long and weigh 9.3g. They have a slender conical black bill. The male is glossy blue-black, with a black tail and wings; the white inner underwing is visible in flight or display. Female and immature birds have brown upperparts and dark-streaked buff underparts.
Blue-black Grassquit feeds mainly on seeds. It is quite gregarious, and forms communal evening roosts.
The male has a jumping display, often performed for long periods, which gives rise to the local name Johnny Jump-up. This is accompanied by a persistent wheezing jweeee call.