Great-billed Seed-Finch

The great-billed seed finch is sexually dimorphic. They have an extremely large and thick bill, that is chalky white in males and black in females. The beak volume is about 840mm³. The males are black with white or white and black under wing-coverts. The females have a warm brown back and a buffy brown belly with white under wing-coverts. The females are very similar to other adult females of the Sporophila genus. Both the male and female great-billed seed finch are very similar in appearance to the male and female large-billed seed finch. It is a medium-sized finch at around 14.5–16.5 cm (5.7–6.5 in) in length. The juvenile is similar in appearance to the female. Sexual dimorphism presents itself in males when they begin to sing. The male juvenile eventually moults its black feathers, having a patchy appearance for several months until it is fully black. Due to their similarity with other species, sexual dimorphism, and juvenile appearance, great-billed seed finches can be very difficult to identify morphologically. The eggs of the great-billed seed finch are grayish white with black blotches and light brown spots.

The great-billed seed finch exists in two separate populations in South America. The southern population is found in the Cerrado and in the Cerrado enclaves into the transition zones in Atlantic Forest. The northern population is found in the northern Amazon rainforest. The great-billed seed finch is specialized to live in humid environments and is often associated with flooded areas and marshy borders.

The great-billed seed finch is predominantly granivorous and feeds mainly on seeds of many species in the Cyperaceae family. They are usually found in pairs. Not much more is known.