Masked Crimson Tanager

The masked crimson tanager is about 17 cm (6.7 in) long and weighs 27 to 36 g (0.95 to 1.3 oz). It has a heavy bill with a wide base to the mandible. The species is sexually dimorphic though not dramatically so. Adult males have a black mask from the base of the forehead and the lower throat to past the eye. The rest of their head and neck and most of their body are shiny red. Their mantle, longer uppertail coverts, wings, and tail are jet-black. The center of their breast and belly and their thighs are also black. Their rear flanks and undertail coverts usually have some black mixed in the red. Adult females have a similar pattern to males but are usually duller overall and their breast and belly patch are dusky rather than black. Both sexes have a reddish brown iris, a black maxilla, a white mandible with a black tip, and dark horn-gray legs. Immature birds resemble adults but are brick red and dusky instead of bright red and black.

The masked crimson tanager is a bird of the western and central Amazon Basin. It is found from the Bogotá area of Colombia south and southeast to the east of the Andes to Ecuador and Peru. There are also small isolated populations in Guaviare and Guainía departments. From Colombia its range continues south through eastern Ecuador and eastern Peru. It might also continue into Bolivia but the South American Classification Committee has only unconfirmed records in that country. From extreme southeastern Colombia and eastern Peru its range continues east into Brazil mostly south of the Amazon almost to its mouth in northeastern Pará. The masked crimson tanager inhabits várzea forest, brushy areas, secondary forest, and other vegetative communities along oxbow lakes and rivers. It sometimes is found a short distance from water in brushy forest clearings. In elevation it ranges up to 500 m (1,600 ft) in Colombia, to 600 m (2,000 ft) in Ecuador, and to 600 m (2,000 ft) and locally to 1,100 m (3,600 ft) in Peru.

The masked crimson tanager feeds on arthropods and fruits. It typically forages in groups of as many as 12 individuals that usually include both adults and young or first-year birds. The groups are described as "ebullient [and] flashy...enlivening the scene wherever they go". The groups sometimes forage with silver-beaked tanagers (R. carbo) or as part of a mixed-species feeding flock but more often away from them. It usually forages up to the forest's mid-level but occasionally as high as 25 m (80 ft) or more above the ground. It takes most arthropods from foliage. At a feeding station in Peru the species was dominant over silver-beaked tanagers.