A finch endemic to Cocos Island, Costa Rica, using the island's varied habitats.
Adult males are entirely black, while females are dark brown above with faint olive-brown streaking and buff underparts. The bird is about 12 cm long and weighs about 12.5 g. Its bill and legs are black; juveniles resemble females but have a yellow bill.
It moves actively in pairs or small groups. Its loose, ball-shaped nest has a side entrance and is placed 2–9 m high near a branch tip. It lays two white eggs marked with brown spots. Nesting occurs throughout the year, with most activity from January to May.
An extinction-risk assessment has not been added yet.