The Cocos Island Finch is the most common land bird in Costa Rica, averaging at 12 cm long. The males are all black and have a thin bill. The females have a blackish-brown back and their underparts are indistinctly streaked olive-brown. They live in many different habitats including hibiscus thickets along the coast, woodland, open country and closed-canopy forest. They eat fruits, especially Cecropia pittieri, they also feed on nectar from Hibiscus tiliaceus, and they eat the vegetation primarily on the vine tangles. Their call is a prolonged and buzzy song, rising at the end, and often preceded by piercing, metallic note.