Blue-black Grassquit

How to find it

Look in fields and along fence lines. Scan fence lines and grass stalks for a small black bird that leaps up from its perch. The buzzy phrase given at the top of each jump helps you find it. Roadsides work well, especially outside the breeding season when flocks gather. On a trip we build, town edges can work too: a visitor photographed one darting in and out of long grass and bamboo along a stream beside a parking lot in Alajuela. Gardens hold it only if they have a large unmowed area.

How to recognise it

This is a tiny bird, about 9 to 11 cm long, with a fairly long cone-shaped bill. Adult males are mostly black with a dark blue shine. A white patch under the wing usually shows only in flight.

The glossy blue-black breeding plumage of the male is seen only in the wet summer season. Young and molting birds show patches of blue-black and brown.

Females are warm brown above with faint darker streaks, and warm buff below, sometimes with a cinnamon wash on the breast. Two faint wing bars may show. A Costa Rican source says she is streaked more heavily below than the other small seedeaters.

What it sounds like

Recording: Rodrigo Paiva Lázaro, CC BY 4.0, source, read 4 Nov 2026.

Behaviour and diet

Breeding males sing from a perch on a fence or grass stem. They hop up briefly, flash the white under the wing, then land on the same perch, and they may repeat this for minutes. Males sing and display for long periods, and the jump may help other grassquits see the male through thick grass. Sometimes a male claps his wings together while jumping, making a mechanical sound.

It eats mainly seeds. Outside the breeding season it usually travels in flocks, often with other seedeaters (Sporophila), and is easy to spot beside roads.

Where it lives

It is found across Costa Rica except the Central Highlands, with an upper elevation limit in the country of about 1,700 m. A Costa Rican source calls it a common resident from both coasts up to that height, and also local at higher elevations in the central part of the country.

Across its whole range it is common in brushy and weedy fields, farms and other open grassland in the tropical lowlands. It is scarcer where forest dominates and is mostly found below 1,000 m. In Costa Rica it also uses disturbed, urban edge areas.

When to see it

The male's glossy blue-black breeding plumage is worn only in the wet summer season, so the best looks at a fully glossy male come then. At other times males look patchy blue-black and brown.

Similar birds

The Blue Seedeater looks much like a male Blue-black Grassquit but is more sparrow-shaped and skulks in cloud forest, while the grassquit is the bird of open lowland fields. Two other small black finches are dull black with larger, stronger bills, whereas the grassquit male is metallic blue with a slimmer bill. Breeding male Indigo Bunting is much lighter blue overall. Blue-black Grassquit, Yellow-faced Grassquit and Variable Seedeater are the three most common small seed-eaters a visitor will meet.

Names and lore in Costa Rica

Besides the official Spanish name, Costa Rican names listed for it are Brea, Pius, Piusillo Negro and Saltapalito. The scientific species name comes from a Tupi word for a bird that flies up and down, which fits its jumping display.

Status and conservation

It is a resident (R) on the AOCR list, considered common in Costa Rica and Least Concern globally, with a very large and increasing population.

Photography tips

Watch a fence line or grass stem where a male is singing, since he returns to the same perch after each jump. The buzzy note at the top of each jump tells you when to be ready.