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The Blue-Black Grassquit is a very small bird. It was previously classified in the bunting and American sparrow family but has now been re-classified as a bird in the tanager family, Thraupidae.          

Male adult Blue-Black Grassquits have glossy blue-black plumage with a black tail and wings; the white inner underwing is visible in flight or display. Female and immature birds have brown upper parts and dark-streaked buff underparts. They have a slender conical black bill and there feet are grey. Adults are around  10 cm long and weigh 9 grams. Blue-Black Grassquit sings from a perch. It utters persistent wheezy, buzzy “duezz-uu”, usually while it performs short vertical jumps with fanned tail. The call is a sharp, high-pitched, slightly liquid “tsick” or “sip”.

Blue-Black Grassquits are a wide spread species of Central America from Mexico, southwards through Brazil to northern Chile and Argentina.  They frequent grassy clearings, weedy pastures, open places such as cultivated areas and gardens. It can be seen at forest edges. It is visible up to 2200 metres of elevation.

Blue-Black Grassquits are basically small seed-eaters, but they will also feed on small insects. The type of seeds eaten depend on what plant species are available. They will also invite themselves to garden feeders when available.  When feeding they are usually seen alone or in pairs, sometimes in loose flocks at the food sources. 

Breeding season probably occurs from May-June to late August. Blue-Black Grassquits seem to be monogamous. The courtship display consists of several repeated vertical jumps up to 90 cm from a perch. These short flights allow the male to display a white axillary spots on the underwings while it utters a short buzzy song. It descends head first, and repeats this display every few seconds.The nest is cup-shaped and made with stiff plant fibres at the bottom, and marsh grasses. It is often built among clumps of grass or low in shrubs. This nest is very rigid and built in a loose manner. It is usually unlined. The female lays between 2 to 3 greenish or bluish-white eggs, with brown markings. The eggs are incubated for around 12, mainly by female, but the male will replace her when she wants to forages for food. Both parents feed the young. The nesting period is relatively short and the nestlings fledge after 12 days. Blue-Black Grassquits are known to use the same nest-site or territory for several years.

Blue-Black Grassquits is a common species and even abundant in suitable habitat. This species is not threatened at this moment and therefore it is classified as a species ”of least concern”.

Photos of the Blue-Black Grassquits were taken at Morro do Moreno - Vila Velha - ES