Black-bellied Tanager

The Huallaga tanager is 16 to 18 cm (6.3 to 7.1 in) long; one male weighed 25 g (0.88 oz). It has a heavy bill with a wide base to the mandible. The species is sexually dimorphic though not dramatically so. Adult males of the nominate subspecies have a dark red or reddish brown head, breast, and upper back. The rest of their of their back is black and their rump and undertail coverts bright red. Their wings and tail are black. The center of their belly is black and the rest of their underparts below the breast bright red. Adult females have a similar pattern to males but are usually duller overall and have no black. Their head is reddish brown with often a paler red area around the bill. Their back, throat, upper breast, wings, and tail are reddish brown and their rump and uppertail coverts redder. Their lower breast, belly, and undertail coverts are cinnamon-red with no black center. Subspecies R. m. transitus is similar to the nominate. However, males have a redder center to their back and a paler throat and breast with less contrast with the lower breast. Both sexes of both subspecies have a reddish brown iris, dusky gray legs, and a dusky maxilla. Males have a silvery white mandible with a black tip and females a bluish gray mandible.

The Huallaga tanager is restricted to the valleys of the Mayo and Huallaga rivers, mostly in San Martín and Huánuco departments of north-central Peru. In elevation it ranges between 500 and 1,800 m (1,600 and 5,900 ft). The nominate subspecies is the more northerly; it is found from the Mayo valley south to the central Huallaga valley. Subspecies R. m. transitus is found in the upper Huallaga valley. The species primarily inhabits secondary forest. It occurs in lesser numbers on the edges of lowland evergreen forest, forest along rivers, and in scrublands.

The Huallaga tanager's diet and foraging behavior have not been studied but they are believed to be similar to those of the silver-beaked tanager (R. carbo), which see here.