Chestnut-bellied Euphonia

The chestnut-bellied euphonia is about 11 cm (4.3 in) long and weighs 15 to 16.5 g (0.53 to 0.58 oz). It is a smallish euphonia with a stout bill. The species is sexually dimorphic. Adult males have a glossy metallic blue head, breast, and upperparts. Their flight feathers and tail are dusky with a metallic blue tinge and metallic blue feather edges. A patch of elongated golden-yellow pectoral feathers protrudes in front of the wing. Their underparts below the breast are dark chestnut. Adult females have a yellowish forecrown and face, a gray crown and nape, and olive upperparts, wings, and tail. Their sides and flanks are yellow-olive, their vent and undertail coverts dark rufous, and the rest of their underparts gray. Both sexes have a dark brown iris, a blackish maxilla, a blue-gray mandible with a blackish tip, and dark gray legs and feet.

The chestnut-bellied euphonia has a small isolated population in eastern Brazil's Pernambuco and Alagoas states. Its contiguous range in Brazil extends south from central Mato Grosso and southern Bahia to central Rio Grande do Sul and continues west into eastern Paraguay and far northeastern Argentina's Misiones Province. It inhabits the canopy, edges, and clearings of humid forest. It is found in lowlands in Argentina but reaches 1,300 m (4,300 ft) in Brazil.

The chestnut-bellied euphonia feeds primarily on small fruits, and also includes smaller amounts of arthropods in its diet. It mostly forages singly, in pairs, and in small groups, and regularly joins mixed-species feeding flocks. It forages primarily from the forest's mid-level to the canopy.