Thick-billed Seed-Finch

How to find it

Scan roadside hedgerows and weedy edges, where it mixes with common seedeaters and grassquits that are usually easy to watch. Go through each flock rather than stopping at the first black bird, because it can sit among many Variable Seedeaters. One birder and a local guide found it along the approach road to the Arenal Hanging Bridges, near the Lake Arenal dam, a first sighting for a guide who had lived in the area all his life. Early morning is worth the effort, since the one listener who described the song heard it only then. A boat trip on the Medio Queso wetlands has also put a few in view.

How to recognise it

Start with the bill. Both sexes have a notably large, thick bill, and in the male the upper edge is straight.

The male is almost all black, with a small white patch on the wing. In flight he shows white at the base of the flight feathers, forming a white wing band.

The female is plain rich brown and lacks the white.

The whole bird is tiny, about 11.5 cm long, so the heavy bill stands out all the more. A Costa Rican guide advises ignoring the black colour and the white wing spot and looking at bill shape. Photos can make the shape look less clear-cut than it is in life.

What it sounds like

Recording: keesgroenendijk, CC BY 4.0, source, read 4 Nov 2026.

Behaviour and diet

It eats mainly grain and seeds, plus some fruit and insects. One photo from Costa Rica shows it feeding on the Müller bodies of a young guarumo (Cecropia) tree.

It shares pasture, roadsides and young second growth with common seedeaters and grassquits. Across its range the nest is a cup of fine rootlets, grass and hair, set 0.8 to 2.5 m up in a shrub or tree, and the female lays two eggs.

Where it lives

In Costa Rica it occurs in wet and very wet forest, secondary growth, forest edges, open areas and roadsides. Across its wider range it prefers tall grass along rivers, weedy fallow fields and scrub, which fits the hedgerows and pasture edges where birders find it here.

One subspecies (salvini) covers the country except the southwest, where a second (ochrogyne) lives, so birds can be found in both the north and the south. One male was photographed in Caribbean rainforest at about 281 m, and a song was recorded at 50 m in Puntarenas.

When to see it

Costa Rican sightings reported include February at Arenal and Las Esquinas, January at Sarapiquí, March in San Carlos and July at Ciudad Neily, but none shows a seasonal pattern. Across its range the breeding season is given as April to September.

Similar birds

The male looks much like the all-black Caribbean-slope form of the Variable Seedeater, but the seed-finch has a larger bill with a straight upper edge, where the seedeater's is shorter and stubbier. On the Pacific slope, male Variable Seedeaters have a white belly, rump and collar, so they are not easily mistaken there. The female seed-finch is rich brown, while the female Variable Seedeater is plain brownish olive. The female also resembles the female Blue Seedeater (Amaurospiza concolor), but the seed-finch is larger. The Nicaraguan (Pink-billed) Seed-Finch has a massive pinkish bill in the male, and some Costa Rican records may be that split species.

Names and lore in Costa Rica

Costa Ricans use the name Semillero Picogrueso. Other Spanish names elsewhere are semillero piquigrueso, semillero de pico grueso and arrocero piquigrueso (Colombia).

Status and conservation

The Official List of the Birds of Costa Rica marks it as a resident (R), and the IUCN lists it as Least Concern.

Photography tips

Scan roadside hedgerows and weedy edges, where it shares pasture, roadsides and young second growth with common seedeaters and grassquits. Check bill shape in the field, since photos can make it look less clear-cut than it is in life.